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Ee2259 lab-manual

G
Gopinath.B.L Naidu

This document contains the syllabus and procedures for experiments in the Electrical Machines I Lab. The experiments focus on obtaining characteristics of DC machines like generators and motors, as well as transformers. Key experiments include open/load characteristics of DC generators and motors, efficiency tests, and open/short circuit tests for transformers. Precautions are outlined and tabular columns provided to record readings and calculate performance parameters like efficiency.

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RAJALAKSHMI ENGINEERING COLLEGE THANDALAM – 602 105. DEPARTMENT OF EEE LAB MANUAL CLASS : II YEAR EEE SEMESTER : IV SEM SUBJECT CODE : EE2259 SUBJECT : Electrical Machines I Lab
SYLLABUS EE2259 -- ELECTRICAL MACHINES LABORATORY – I AIM To expose the students to the operation of D.C. machines and transformers and give them experimental skill. 1. Open circuit and load characteristics of separately and self excited DC shunt generators. 2. Load characteristics of DC compound generator with differential and cumulative connection. 3. Load characteristics of DC shunt and compound motor. 4. Load characteristics of DC series motor. 5. Swinburne’s test and speed control of DC shunt motor. 6. Hopkinson’s test on DC motor – generator set. 7. Load test on single-phase transformer and three phase transformer connections. 8. Open circuit and short circuit tests on single phase transformer. 9. Sumpner’s test on transformers. 10. Separation of no-load losses in single phase transformer.
Ex.No.1 OPEN CIRCUIT CHARACTERISTICS OF SELF EXCITED DC SHUNT GENERATOR AIM: To obtain open circuit characteristics of self excited DC shunt generator and to find its critical resistance. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-1)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1250Ω , 0.8A Wire Wound 2 4 SPST Switch - - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be in minimum resistance position at the time of starting and stopping the machine. 2. The field rheostat of generator should be in maximum resistance position at the time of starting and stopping the machine. 3. SPST switch is kept open during starting and stopping. PROCEDURE: 1. Connections are made as per the circuit diagram.
2. After checking minimum position of motor field rheostat, maximum position of generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. By adjusting the field rheostat, the motor is brought to rated speed. 4. Voltmeter and ammeter readings are taken when the SPST switch is kept open. 5. After closing the SPST switch, by varying the generator field rheostat, voltmeter and ammeter readings are taken. 6. After bringing the generator rheostat to maximum position, field rheostat of motor to minimum position, SPST switch is opened and DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: Field Armature S.N Current Voltage o. If (Amps) Eo (Volts) MODEL GRAPH: Eo (Volts) Critical Resistance = Eo / If Ohms If Eo If (Amps)
RESULT: Thus open circuit characteristics of self excited DC shunt generator are obtained and its critical resistance is determined.
Ex.No.2 LOAD CHARACTERISTICS OF SELF EXCITED DC SHUNT GENERATOR AIM: To obtain internal and external characteristics of DC shunt generator. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MC 1 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1200Ω , 0.8A Wire Wound 2 4 Loading Rheostat 5KW, 230V - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be at minimum position. 2. The field rheostat of generator should be at maximum position. 3. No load should be connected to generator at the time of starting and stopping. PROCEDURE:
1. Connections are made as per the circuit diagram. 2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field rheostat of generator. 4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted. 5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of DC shunt motor to minimum position, DPST switch is opened.
Ee2259 lab-manual
DETERMINATION OF ARMATURE RESISTANCE: Fuse + - + A 27A (0-20)A D MC P S A1 T + 220V DC G V (0-300)V S MC Supply W - I T LOAD C 5 KW, 230V A2 H 27A - Fuse PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I
TABULAR COLUMN: S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) TABULAR COLUMN: Field Load Terminal Ia = IL + If S.No. Current Current Voltage Eg =V + Ia Ra (Amps) If (Amps) IL (Amps) (V) Volts (Volts) FORMULAE:
Eg = V + Ia Ra (Volts) Ia = IL + If (Amps) Eg : Generated emf in Volts V : Terminal Voltage in Volts Ia : Armature Current in Amps IL : Line Current in Amps If : Field Current in Amps Ra : Armature Resistance in Ohms MODEL GRAPH: VL, E (Volts) E Vs IL (Int Char) V Vs IL (Ext Char) RESULT: If, IL (Amps)
Thus the load characteristics of self excited DC shunt generator is obtained.
Ex.No.3 OPEN CIRCUIT CHARACTERISTICS OF SEPARATELY EXCITED DC SHUNT GENERATOR AIM: To obtain open circuit characteristics of separately excited DC shunt generator. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-1)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1250Ω , 0.8A Wire Wound 2 4 Tachometer (0-1500)rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be in minimum resistance position at the time of starting and stopping the machine. 2. The field rheostat of generator should be in maximum resistance position at the time of starting and stopping the machine.
PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking minimum position of motor field rheostat, maximum position of generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. By adjusting the field rheostat, the motor is brought to rated speed. 4. By varying the generator field rheostat, voltmeter and ammeter readings are taken. 5. After bringing the generator rheostat to maximum position, field rheostat of motor to minimum position, DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: Field Current Armature Voltage S.No. If (Amps) Eo (Volts) MODEL GRAPH: Eo (Volts) If (Amps)
RESULT: Thus open circuit characteristics of separately excited DC shunt generator is obtained.
Ex.No.4 LOAD CHARACTERISTICS OF SEPARATELY EXCITED DC SHUNT GENERATOR AIM: To obtain internal and external characteristics of DC separately excited DC shunt generator. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MC 1 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1200Ω , 0.8A Wire Wound 2 4 Loading Rheostat 5KW, 230V - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be at minimum position. 2. The field rheostat of generator should be at maximum position. 3. No load should be connected to generator at the time of starting and stopping. PROCEDURE: 1. Connections are made as per the circuit diagram.
2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field rheostat of generator. 4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted. 5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of DC shunt motor to minimum position, DPST switch is opened.
DETERMINATION OF ARMATURE RESISTANCE:
Fuse + - + A 27A (0-20)A D MC P S A1 T + 220V DC G V (0-300)V S MC Supply W - I T LOAD C 5 KW, 230V A2 H 27A - Fuse PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I TABULAR COLUMN:
S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) TABULAR COLUMN: Field Load Terminal Ia = IL + If S.No. Current Current Voltage Eg =V + Ia Ra (Amps) If (Amps) IL (Amps) (V) Volts (Volts) FORMULAE: Eg = V + Ia Ra (Volts) Ia = IL + If (Amps)
Eg : Generated emf in Volts V : Terminal Voltage in Volts Ia : Armature Current in Amps IL : Line Current in Amps If : Field Current in Amps Ra : Armature Resistance in Ohms MODEL GRAPH: VL, E (Volts) E Vs IL (Int Char) V Vs IL (Ext Char) RESULT: If, IL (Amps) Thus load characteristics of separately excited DC shunt generator is obtained.
Ex.No.5 LOAD TEST ON DC SHUNT MOTOR AIM: To conduct load test on DC shunt motor and to find efficiency. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostat 1250Ω , 0.8A Wire Wound 1 4 Tachometer (0-1500) rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. DC shunt motor should be started and stopped under no load condition. 2. Field rheostat should be kept in the minimum position. 3. Brake drum should be cooled with water when it is under load. PROCEDURE: 1. Connections are made as per the circuit diagram.
2. After checking the no load condition, and minimum field rheostat position, DPST switch is closed and starter resistance is gradually removed. 3. The motor is brought to its rated speed by adjusting the field rheostat. 4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no load condition. 5. The load is then added to the motor gradually and for each load, voltmeter, ammeter, spring balance readings and speed of the motor are noted. 6. The motor is then brought to no load condition and field rheostat to minimum position, then DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: Spring Balance Output Input Voltage Current Speed Torque Reading Power Power Efficiency S.No. V I (S1∼ S2)Kg N T Pm Pi η % (Volts) (Amps) S1(Kg) S2(Kg) (rpm) (Nm) (Watts) (Watts) Circumference of the Brake drum = cm.
FORMULAE: Circumference R = ------------------- m 100 x2π Torque T = (S1 ∼ S2) x R x 9.81 Nm Input Power Pi = VI Watts 2π NT Output Power Pm = ------------ Watts 60 Output Power Efficiency η % = -------------------- x 100% Input Power
MODEL GRAPHS: Torque T (Nm) Speed N (rpm) Efficiency % Speed N (rpm) y y3 y2 y1 η N T x Torque T (Nm) Output Power (Watts) RESULT: Thus load test on DC shunt motor is conducted and its efficiency is determined.
Ex.No.6 LOAD TEST ON DC COMPOUND MOTOR AIM: To conduct load test on DC compound motor and to find its efficiency. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostat 1250Ω , 0.8A Wire Wound 1 4 Tachometer (0-1500) rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. DC compound motor should be started and stopped under no load condition. 2. Field rheostat should be kept in the minimum position. 3. Brake drum should be cooled with water when it is under load.
PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking the no load condition, and minimum field rheostat position, DPST switch is closed and starter resistance is gradually removed. 3. The motor is brought to its rated speed by adjusting the field rheostat. 4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no load condition. 5. The load is then added to the motor gradually and for each load, voltmeter, ammeter, spring balance readings and speed of the motor are noted. 6. The motor is then brought to no load condition and field rheostat to minimum position, then DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: Spring Balance Output Input Voltage Current Speed Torque Reading Power Power Efficiency S.No. V I (S1∼ S2)Kg N T Pm Pi η % (Volts) (Amps) S1(Kg) S2(Kg) (rpm) (Nm) (Watts) (Watts)
FORMULAE: Circumference R = ------------------- m 100 x2π Torque T = (S1 ∼ S2) x R x 9.81 Nm Input Power Pi = VI Watts 2π NT Output Power Pm = ------------ Watts 60 Output Power Efficiency η % = -------------------- x 100% Input Power
MODEL GRAPHS: y3 y2 y1 Torque T (Nm) Speed N (rpm) Efficiency % η Speed N (rpm) N y T Output Power (Watts) x RESULT: Torque T (Nm) Thus load test on DC compound motor is conducted and its efficiency is determined.
Ex.No.7 LOAD CHARACTERISTICS OF DC COMPOUND GENERATOR AIM: To obtain the load characteristics of DC Compound generator under cumulative and differential mode condition. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MC 1 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1200Ω , 0.8A Wire Wound 2 4 Loading Rheostat 5KW, 230V - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be at minimum position. 2. The field rheostat of generator should be at maximum position. 3. No load should be connected to generator at the time of starting and stopping.
PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field rheostat of generator. 4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted. 5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of DC shunt motor to minimum position, DPST switch is opened. 6. The connections of series field windings are reversed the above steps are repeated. 7. The values of voltage for the particular currents are compared and then the differential and cumulative compounded DC generator is concluded accordingly.
Ee2259 lab-manual
TABULAR COLUMN: Cumulatively Compounded Differentially Compounded S.No. V (Volts) IL (Amps) V (Volts) IL (Amps) MODEL GRAPH: V (Volts) Cumulatively Compounded Differentially Compounded IL (Amps)
RESULT: Thus load characteristics of DC compound generator under cumulative and differential mode condition are obtained
Ex.No.8 LOAD TEST ON DC SERIES MOTOR AIM: To conduct load test on DC Series Motor and to find efficiency. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20)A MC 1 2 Voltmeter (0-300)V MC 1 (0-3000) 3 Tachometer Digital 1 rpm 4 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The motor should be started and stopped with load 2. Brake drum should be cooled with water when it is under load.
PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking the load condition, DPST switch is closed and starter resistance is gradually removed. 3. For various loads, Voltmeter, Ammeter readings, speed and spring balance readings are noted. 4. After bringing the load to initial position, DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: Spring Balance Output Input Voltage Current Speed Torque Reading Power Power Efficiency S.No. V I (S1∼ S2)Kg N T Pm Pi η % (Volts) (Amps) S1(Kg) S2(Kg) (rpm) (Nm) (Watts) (Watts)
FORMULAE: Circumference R = ------------------- m 100 x2π Torque T = (S1 ∼ S2) x R x 9.81 Nm Input Power Pi = VI Watts 2π NT Output Power Pm = ------------ Watts 60 Output Power Efficiency η % = -------------------- x 100% Input Power
MODEL GRAPH: Torque T (Nm) Speed N (rpm) Efficiency % y3 y2 y1 T E N RESULT: Thus load test on DC series motor is conducted and its efficiency is determined. Output Power (Watts)
Ex. No. 9 SWINBURNE’S TEST AIM: To conduct Swinburne’s test on DC machine to determine efficiency when working as generator and motor without actually loading the machine. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300) V MC 1 Wire 3 Rheostats 1250Ω , 0.8A 1 Wound 4 Tachometer (0-3000) rpm Digital 1 5 Resistive Load 5KW,230V - 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: The field rheostat should be in the minimum position at the time of starting and stopping the motor PROCEDURE:
1. Connections are made as per the circuit diagram. 2. After checking the minimum position of field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. By adjusting the field rheostat, the machine is brought to its rated speed. 4. The armature current, field current and voltage readings are noted. 5. The field rheostat is then brought to minimum position DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMNS: AS MOTOR: Total Output Input V IL Ia 2 Ia Ra Losses Efficiency S. No. Power Power (Volts) (Amps) (Amps) (Watts) W η % (Watts) (Watts) (Watts)
AS GENERATOR: Total Output Input V I1 Ia Ia2Ra Efficiency S. No. Losses Power Power (Volts) (Amps) (Amps) (Watts) η % (Watts) (Watts) (Watts)
TABULAR COLUMN: If Io V S.No. (Amps) (Amps) (Volts) DETERMINATION OF ARMATURE RESISTANCE: Fuse + - + A 27A (0-20)A D MC P S A1 T + 220V DC M V (0-300)V S MC Supply W - I T LOAD C 5 KW, 230V A2 H 27A - Fuse
PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I TABULAR COLUMN: S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) FORMULAE:
Hot Resistance Ra = 1.2 X R Ω Constant losses = VIo – Iao2 Ra watts Where Iao = (Io – If) Amps AS MOTOR: Load Current IL = _____ Amps (Assume 15%, 25%, 50%, 75% of rated current) Armature current Ia = IL – If Amps Copper loss = Ia2 Ra watts Total losses = Copper loss + Constant losses Input Power = VIL watts Output Power = Input Power – Total losses Output power Efficiency η % = ---------------------- X 100% Input Power AS GENERATOR: Load Current IL = _____ Amps (Assume 15%, 25%, 50%, 75% of rated current) Armature current Ia = IL + If Amps Copper loss = Ia2 Ra watts Total losses = Copper loss + Constant losses Output Power = VIL watts
Input Power = Input Power +Total losses Output power Efficiency η % = ----------------------- X 100% Input Power MODEL GRAPH: As a Generator %η As a Motor OUTPUT POWER P0 (W) RESULT: Thus the efficiency of the D.C machine is predetermined by Swinburne’s test.
Ex.No. 10 SPEED CONTROL OF DC SHUNT MOTOR AIM: To obtain speed control of DC shunt motor by a. Varying armature voltage with field current constant. b. Varying field current with armature voltage constant APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300) V MC 1 1250Ω , 0.8A Wire 3 Rheostats Each 1 50Ω , 3.5A Wound 4 Tachometer (0-3000) rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. Field Rheostat should be kept in the minimum resistance position at the time of starting and stopping the motor. 2. Armature Rheostat should be kept in the maximum resistance position at the time of starting and stopping the motor. PROCEDURE:
1. Connections are made as per the circuit diagram. 2. After checking the maximum position of armature rheostat and minimum position of field rheostat, DPST switch is closed (i) Armature Control: 1. Field current is fixed to various values and for each fixed value, by varying the armature rheostat, speed is noted for various voltages across the armature. (ii) Field Control: 1. Armature voltage is fixed to various values and for each fixed value, by adjusting the field rheostat, speed is noted for various field currents. 2. Bringing field rheostat to minimum position and armature rheostat to maximum position DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: (i) Armature Voltage Control: If1 = If2 = If3 = Armature Speed Armature Speed Armature Speed S.No. Voltage N (rpm) Voltage N (rpm) Voltage N (rpm) Va ( Volts) Va ( Volts) Va ( Volts) (ii) Field Control: Va1 = Va2 = Va3 = Field Speed Field Speed Field Speed S.No. Current N (rpm) Current N (rpm) Current N (rpm) If (A) If (A) If (A) Speed N (rpm) Speed N (rpm) If1 If2 If3 MODEL GRAPHS: Va1 Va3 Va2 If (Amps) Va (Volts)
RESULT: Thus the speed control of DC Shunt Motor is obtained using Armature and Field control methods. Ex.No. 11
HOPKINSON’S TEST AIM: To conduct Hopkinson’s test on a pair of identical DC machines to pre-determine the efficiency of the machine as generator and as motor. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-1)A MC 1 1 Ammeter (0-20) A MC 2 (0-300) V MC 1 2 Voltmeter (0-600)V MC 1 Wire 3 Rheostats 1250Ω , 0.8A 2 Wound 4 Tachometer (0-3000) rpm Digital 1 5 Resistive Load 5KW,230V - 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECATUIONS: 1. The field rheostat of the motor should be in the minimum position at the time of starting and stopping the machine. 2. The field rheostat of the generator should be in the maximum position at the time of starting and stopping the machine. 3. SPST switch should be kept open at the time of starting and stopping the machine.
PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking the minimum position of field rheostat of motor, maximum position of field rheostat of generator, opening of SPST switch, DPST switch is closed and starting resistance is gradually removed. 3. The motor is brought to its rated speed by adjusting the field rheostat of the motor. 4. The voltmeter V1 is made to read zero by adjusting field rheostat of generator and SPST switch is closed. 5. By adjusting field rheostats of motor and generator, various Ammeter readings, voltmeter readings are noted. 6. The rheostats and SPST switch are brought to their original positions and DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: Motor Generator Total Stray Supply Armature Armature Stray Loss S.No. Voltage I1 I2 I3 I4 I1 + I2 Cu Loss Cu Loss losses Per M/c w/2 V(Volts) (Amps) (Amps) (Amps) (Amps) (Amps) W (watts) W(watts) W (watts) (watts)
AS MOTOR: Motor Total Armature stray Output Input V I1 I2 I3 Field Loss Losses Efficiency S.No. Cu Loss losses Power Power (Volts) (Amps) (Amps) (Amps) (Watts) W η % W (Watts) /2(Watts) (Watts) (Watts) (Watts) AS GENERATOR: Motor Armature Total Stray Output Cu Loss Field Loss Losses Input Power Efficiency V I1 I2 losses Power S.No. W (Watts) W (Watts) η % (Volts) (Amps) (Amps) /2(Watts) (Watts) (Watts) (Watts)
Ee2259 lab-manual
PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I TABULAR COLUMN: S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) FORMULAE:
Input Power = VI1 watts Motor armature cu loss = (I1+ I2)2 Ra watts Generator armature cu loss = I22 Ra watts Total Stray losses W = V I1 - (I1+I2)2 Ra + I22 Ra watts. Stray loss per machine = W/2 watts. AS MOTOR: Input Power = Armature input + Shunt field input = (I1+ I2) V + I3V = (I1+I2+I3) V Total Losses = Armature Cu loss + Field loss + stray loss = (I1 + I2)2 Ra + VI3 + W/2 watts Input power – Total Losses Efficiency η % = ------------------------------------- x 100% Input Power AS GENERATOR: Output Power = VI2 watts Total Losses = Armature Cu loss+ Field Loss + Stray loss = I22 Ra + VI4 + W/2 watts Output power Efficiency η % = -------------------------------------- x 100% Output Power+ Total Losses
MODEL GRAPH: As a Generator %η As a Motor OUTPUT POWER P0 (W) RESULT: Thus Hopkinson’s test is conducted on a pair of identical DC machines the efficiency of the machine as generator and as motor are pre- determined Ex.No. 12
LOAD TEST ON A SINGLE PHASE TRANSFORMER AIM: To conduct load test on single phase transformer and to find efficiency and percentage regulation. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-10)A MI 1 1 Ammeter (0-5) A MI 1 (0-150)V MI 1 2 Voltmeter (0-300) V MI 1 (300V, 5A) Upf 1 3 Wattmeter (150V, 5A) Upf 1 1φ , (0- 4 Auto Transformer - 1 260)V 5 Resistive Load 5KW, 230V - 1 6 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. Auto Transformer should be in minimum position. 2. The AC supply is given and removed from the transformer under no load condition. PROCEDURE: 1. Connections are made as per the circuit diagram.
2. After checking the no load condition, minimum position of auto transformer and DPST switch is closed. 3. Ammeter, Voltmeter and Wattmeter readings on both primary side and secondary side are noted. 4. The load is increased and for each load, Voltmeter, Ammeter and Wattmeter readings on both primary and secondary sides are noted. 5. Again no load condition is obtained and DPST switch is opened.
Ee2259 lab-manual
TABULAR COLUMN: Primary Secondary Input Output Efficiency % S.No. Load V1 I1 W1 V2 I2 W2 Power Power η Regulation (Volts) (Amps) (Watts) (Volts) (Amps) (Watts) W1 x MF W2 x MF %
FORMULAE: Output Power = W2 x Multiplication factor Input Power = W1 x Multiplication factor Output Power Efficiency η % = -------------------- x 100% Input Power VNL - VFL (Secondary) Regulation R % = ------------------------------ x 100% VNL MODEL GRAPHS: Efficiency η % Regulation R % η R RESULT: Thus the load test on single phase transformer is conducted. Output Power (Watts)
Ex.No. 13 OPEN CIRCUIT & SHORT CIRCUIT TEST ON A SINGLE PHASE TRANSFORMER AIM: To predetermine the efficiency and regulation of a transformer by conducting open circuit test and short circuit test and to draw equivalent circuit. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MI 1 1 Ammeter (0-5) A MI 1 2 Voltmeter (0-150)V MI 2 (150V, 5A) LPF 1 3 Wattmeter (150V, 5A) UPF 1 4 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. Auto Transformer should be in minimum voltage position at the time of closing & opening DPST Switch. PROCEDURE: OPEN CIRCUIT TEST:
1. Connections are made as per the circuit diagram. 2. After checking the minimum position of Autotransformer, DPST switch is closed. 3. Auto transformer variac is adjusted get the rated primary voltage. 4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted. 5. Auto transformer is again brought to minimum position and DPST switch is opened. SHORT CIRCUIT TEST: 1. Connections are made as per the circuit diagram. 2. After checking the minimum position of Autotransformer, DPST switch is closed. 3. Auto transformer variac is adjusted get the rated primary current. 4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted. 5. Auto transformer is again brought to minimum position and DPST switch is opened.
Ee2259 lab-manual
Ee2259 lab-manual
TABULAR COLUMN: OPEN CIRCUIT TEST: Vo Io Wo (Volts) (Amps) (Watts) SHORT CIRCUIT TEST: Vsc Isc Wsc (Volts) (Amps) (Watts) FORMULAE: Core loss: Wo = VoIo cos φ o
Wo Wo cos φ o = ------- φ o = cos-1 ------- Vo Io Vo Io Iω = Io cos φ o (Amps) Iµ = Io sin φ o (Amps) V0 V0 Wsc Ro = ------- Ω Xo = ------- Ω Ro2 = ------- Ω Iω Iµ Isc2 Vsc Xo2 = ( Zo2 - Ro22)1/2 Zo2 = ------- Ω Isc V2 R02 X02 K= ------- = 2 Ro1 = ------- Ω Xo1 = ------- Ω V1 K2 K2 Percentage Efficiency: for all loads and p.f. Output Power (X) x KVA rating x 1000 x cos φ Efficiency η % = -------------------- = ------------------------------------------------ Input Power Output power + losses
(X) x KVA rating x 1000 x cos φ = ------------------------------------------------------------- (X) x KVA rating x 1000 x cos φ + Wo + X2Wsc Percentage Regulation: (X) x Isc (Ro2 cos φ ± Xo2sin φ ) x 100 = lagging + - = leading R% = -------------------------------------- V2 Where X is the load and it is 1 for full load, ½ for half load, ¾ load, ¼ load etc.. and the power factor is, upf, o.8 p.f lag and 0.8 p.f lead ISC R X o o1 EQUIVALENT CIRCUIT: o1 R I o L V O o A D R X o o ZL′ = ZL/K2 N
MODEL GRAPHS: Efficiency η % % lagging Output power (Watts) Power factor % leading
RESULT: Thus the efficiency and regulation of a transformer is predetermined by conducting open circuit test and short circuit test and the equivalent circuit is drawn.
Ex.No. 14 SUMPNER’S TEST AIM : To predetermine the efficiency and regulation of a given single phase Transformer by conducting back-to-back test and also to find the parameters of the equivalent circuit. APPARATUS REQUIRED: S. No. Name of the Apparatus Range Type Quantity 1 Auto Transformer (0-270) V - 2 300 V, 10A LPF 1 2 Wattmeter 75 V, 5 A UPF 1 (0-2) A MI 1 3 Ammeter (0-20) A MI 1 (0-75) V MI 1 4 Voltmeter (0-150) V MI 1 5 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. Auto Transformer whose variac should be in zero position, before switching on the ac supply. 2. Transformer should be operated under rated values.
PROCEDURE: 1. Connections are made as shown in the circuit diagram. 2. Rated voltage of 110V is adjusted to get in voltmeter by adjusting the variac of the Auto Transformer which would be in zero before switching on the supply at the primary side. 3. The readings of voltmeter, ammeter and wattmeter are noted on the primary side. 4. A voltmeter is connected across the secondary and with the secondary supply off i.e switch S is kept open. The voltmeter reading is noted. 5. If the reading of voltmeter reads higher voltage, the terminals of any one of secondary coil is interchanged in order that voltmeter reads zero. 6. The secondary is now switched on and SPST switch is closed with variac of auto transformer is zero. 7. After switching on the secondary the variac of transformer (Auto) is adjusted so that full load rated secondary current flows. 8. Then the readings of wattmeter, Ammeter and voltmeter are noted. 9. The Percentage Efficiency and percentage regulation are calculated and equivalent circuit is drawn.
Ee2259 lab-manual
FORMULAE: W1 Core loss of each transformer Wo = ----- Watts 2 W2 Full load copper loss of each transformer Wc = ------ Watts. 2 Wo Io Wo = V1I1 Cos ϕ o ϕ o = Cos-1 --------- I1 = ---- A V1 I1 2 Iw = I1 CosΦ o Iμ = I1 CosΦ V2 = Vs/2 x A Ro = V1 / Iw Xo = V1 / Iμ Ro2 = Wc / I22 Zo2 = V2 / I2 Xo2 = √ Zo22 – Ro22 Copper loss at various loads = I22 Ro2
PERCENTAGE REGULATION: 1. Upf : I2 / V (Ro2 CosΦ o) X 100 2. Lagging pf : I2 / V (Ro2 CosΦ o + Xo2SinΦ o) X 100 3. Leading pf : I2 / V (Ro2 CosΦ o - Xo2SinΦ o) X 100 Output Power (1) Upf : 3Kw (2) Pf : 3Kw CosΦ o Input Power = Output Power + Core loss + Cu loss Output power Efficiency η % = -------------------------- X 100% Input Power
EQUIVALENT CIRCUIT: ISC R X o o1 o1 R I o L V O o A X D o R o N MODEL GRAPHS: Cos φ = 1 % Regulation % Efficiency Cos φ = 0.8 (Lead & Lag Cos φ = 1 Cos φ = 0.8 Lag Cos φ = 0.8 Lead Secondary Current (Amps) Secondary Current (Amps)
RESULT: Thus the efficiency and regulation of a given single phase Transformer is carried out by conducting back-to-back test and the equivalent circuit parameters are found out.
Ex.No. 15 SEPARATION OF NO LOAD LOSSES IN A SINGLE PHASE TRANSFORMER AIM: To separate the eddy current loss and hysteresis loss from the iron loss of single phase transformer. APPARATUS REQUIRED: S. No. Name of the Apparatus Range Type Quantity 1 Rheostat 1250Ω , 0.8A Wire Wound 2 2 Wattmeter 300 V, 5A LPF 1 3 Ammeter (0-2) A MC 1 4 Voltmeter (0-300) V MI 1 5 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. The motor field rheostat should be kept at minimum resistance position. 2. The alternator field rheostat should be kept at maximum resistance position. PROCEDURE: 1. Connections are given as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. The DC motor is started by using the 3 point starter and brought to rated speed by adjusting its field rheostat. 4. By varying the alternator filed rheostat gradually the rated primary voltage is applied to the transformer. 5. The frequency is varied by varying the motor field rheostat and the readings of frequency are noted and the speed is also measured by using the tachometer.
6. The above procedure is repeated for different frequencies and the readings are tabulated. 7. The motor is switched off by opening the DPST switch after bringing all the rheostats to the initial position.
Ee2259 lab-manual
TABULAR COLUMN: S.No. Speed Frequency Voltage Wattmeter Iron loss Wi / f N (rpm) f (Hz) V (Volts) reading Wi (Watts) Joules Watts FORMULAE USED: 1. Frequency, f =(P*NS) / 120 in Hz P = No.of Poles & Ns = Synchronous speed in rpm. 2. Hysteresis Loss Wh = A * f in Watts A = Constant (obtained from graph) 3. Eddy Current Loss We = B * f2 in Watts B = Constant (slope of the tangent drawn to the curve) 4. Iron Loss Wi = Wh + We in Watts Wi / f = A + (B * f) Here the Constant A is distance from the origin to the point where the line cuts the Y- axis in the graph between W i / f and frequency f. The Constant B is Δ(Wi / f ) / Δf Wf y MODEL GRAPH: x A f
RESULT: Thus separation of eddy current and hysteresis loss from the iron loss on a single-phase transformer is conducted.

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Ee2259 lab-manual

  • 1. RAJALAKSHMI ENGINEERING COLLEGE THANDALAM – 602 105. DEPARTMENT OF EEE LAB MANUAL CLASS : II YEAR EEE SEMESTER : IV SEM SUBJECT CODE : EE2259 SUBJECT : Electrical Machines I Lab
  • 2. SYLLABUS EE2259 -- ELECTRICAL MACHINES LABORATORY – I AIM To expose the students to the operation of D.C. machines and transformers and give them experimental skill. 1. Open circuit and load characteristics of separately and self excited DC shunt generators. 2. Load characteristics of DC compound generator with differential and cumulative connection. 3. Load characteristics of DC shunt and compound motor. 4. Load characteristics of DC series motor. 5. Swinburne’s test and speed control of DC shunt motor. 6. Hopkinson’s test on DC motor – generator set. 7. Load test on single-phase transformer and three phase transformer connections. 8. Open circuit and short circuit tests on single phase transformer. 9. Sumpner’s test on transformers. 10. Separation of no-load losses in single phase transformer.
  • 3. Ex.No.1 OPEN CIRCUIT CHARACTERISTICS OF SELF EXCITED DC SHUNT GENERATOR AIM: To obtain open circuit characteristics of self excited DC shunt generator and to find its critical resistance. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-1)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1250Ω , 0.8A Wire Wound 2 4 SPST Switch - - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be in minimum resistance position at the time of starting and stopping the machine. 2. The field rheostat of generator should be in maximum resistance position at the time of starting and stopping the machine. 3. SPST switch is kept open during starting and stopping. PROCEDURE: 1. Connections are made as per the circuit diagram.
  • 4. 2. After checking minimum position of motor field rheostat, maximum position of generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. By adjusting the field rheostat, the motor is brought to rated speed. 4. Voltmeter and ammeter readings are taken when the SPST switch is kept open. 5. After closing the SPST switch, by varying the generator field rheostat, voltmeter and ammeter readings are taken. 6. After bringing the generator rheostat to maximum position, field rheostat of motor to minimum position, SPST switch is opened and DPST switch is opened.
  • 6. TABULAR COLUMN: Field Armature S.N Current Voltage o. If (Amps) Eo (Volts) MODEL GRAPH: Eo (Volts) Critical Resistance = Eo / If Ohms If Eo If (Amps)
  • 7. RESULT: Thus open circuit characteristics of self excited DC shunt generator are obtained and its critical resistance is determined.
  • 8. Ex.No.2 LOAD CHARACTERISTICS OF SELF EXCITED DC SHUNT GENERATOR AIM: To obtain internal and external characteristics of DC shunt generator. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MC 1 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1200Ω , 0.8A Wire Wound 2 4 Loading Rheostat 5KW, 230V - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be at minimum position. 2. The field rheostat of generator should be at maximum position. 3. No load should be connected to generator at the time of starting and stopping. PROCEDURE:
  • 9. 1. Connections are made as per the circuit diagram. 2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field rheostat of generator. 4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted. 5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of DC shunt motor to minimum position, DPST switch is opened.
  • 11. DETERMINATION OF ARMATURE RESISTANCE: Fuse + - + A 27A (0-20)A D MC P S A1 T + 220V DC G V (0-300)V S MC Supply W - I T LOAD C 5 KW, 230V A2 H 27A - Fuse PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I
  • 12. TABULAR COLUMN: S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) TABULAR COLUMN: Field Load Terminal Ia = IL + If S.No. Current Current Voltage Eg =V + Ia Ra (Amps) If (Amps) IL (Amps) (V) Volts (Volts) FORMULAE:
  • 13. Eg = V + Ia Ra (Volts) Ia = IL + If (Amps) Eg : Generated emf in Volts V : Terminal Voltage in Volts Ia : Armature Current in Amps IL : Line Current in Amps If : Field Current in Amps Ra : Armature Resistance in Ohms MODEL GRAPH: VL, E (Volts) E Vs IL (Int Char) V Vs IL (Ext Char) RESULT: If, IL (Amps)
  • 14. Thus the load characteristics of self excited DC shunt generator is obtained.
  • 15. Ex.No.3 OPEN CIRCUIT CHARACTERISTICS OF SEPARATELY EXCITED DC SHUNT GENERATOR AIM: To obtain open circuit characteristics of separately excited DC shunt generator. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-1)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1250Ω , 0.8A Wire Wound 2 4 Tachometer (0-1500)rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be in minimum resistance position at the time of starting and stopping the machine. 2. The field rheostat of generator should be in maximum resistance position at the time of starting and stopping the machine.
  • 16. PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking minimum position of motor field rheostat, maximum position of generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. By adjusting the field rheostat, the motor is brought to rated speed. 4. By varying the generator field rheostat, voltmeter and ammeter readings are taken. 5. After bringing the generator rheostat to maximum position, field rheostat of motor to minimum position, DPST switch is opened.
  • 18. TABULAR COLUMN: Field Current Armature Voltage S.No. If (Amps) Eo (Volts) MODEL GRAPH: Eo (Volts) If (Amps)
  • 19. RESULT: Thus open circuit characteristics of separately excited DC shunt generator is obtained.
  • 20. Ex.No.4 LOAD CHARACTERISTICS OF SEPARATELY EXCITED DC SHUNT GENERATOR AIM: To obtain internal and external characteristics of DC separately excited DC shunt generator. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MC 1 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1200Ω , 0.8A Wire Wound 2 4 Loading Rheostat 5KW, 230V - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be at minimum position. 2. The field rheostat of generator should be at maximum position. 3. No load should be connected to generator at the time of starting and stopping. PROCEDURE: 1. Connections are made as per the circuit diagram.
  • 21. 2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field rheostat of generator. 4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted. 5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of DC shunt motor to minimum position, DPST switch is opened.
  • 23. Fuse + - + A 27A (0-20)A D MC P S A1 T + 220V DC G V (0-300)V S MC Supply W - I T LOAD C 5 KW, 230V A2 H 27A - Fuse PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I TABULAR COLUMN:
  • 24. S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) TABULAR COLUMN: Field Load Terminal Ia = IL + If S.No. Current Current Voltage Eg =V + Ia Ra (Amps) If (Amps) IL (Amps) (V) Volts (Volts) FORMULAE: Eg = V + Ia Ra (Volts) Ia = IL + If (Amps)
  • 25. Eg : Generated emf in Volts V : Terminal Voltage in Volts Ia : Armature Current in Amps IL : Line Current in Amps If : Field Current in Amps Ra : Armature Resistance in Ohms MODEL GRAPH: VL, E (Volts) E Vs IL (Int Char) V Vs IL (Ext Char) RESULT: If, IL (Amps) Thus load characteristics of separately excited DC shunt generator is obtained.
  • 26. Ex.No.5 LOAD TEST ON DC SHUNT MOTOR AIM: To conduct load test on DC shunt motor and to find efficiency. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostat 1250Ω , 0.8A Wire Wound 1 4 Tachometer (0-1500) rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. DC shunt motor should be started and stopped under no load condition. 2. Field rheostat should be kept in the minimum position. 3. Brake drum should be cooled with water when it is under load. PROCEDURE: 1. Connections are made as per the circuit diagram.
  • 27. 2. After checking the no load condition, and minimum field rheostat position, DPST switch is closed and starter resistance is gradually removed. 3. The motor is brought to its rated speed by adjusting the field rheostat. 4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no load condition. 5. The load is then added to the motor gradually and for each load, voltmeter, ammeter, spring balance readings and speed of the motor are noted. 6. The motor is then brought to no load condition and field rheostat to minimum position, then DPST switch is opened.
  • 29. TABULAR COLUMN: Spring Balance Output Input Voltage Current Speed Torque Reading Power Power Efficiency S.No. V I (S1∼ S2)Kg N T Pm Pi η % (Volts) (Amps) S1(Kg) S2(Kg) (rpm) (Nm) (Watts) (Watts) Circumference of the Brake drum = cm.
  • 30. FORMULAE: Circumference R = ------------------- m 100 x2π Torque T = (S1 ∼ S2) x R x 9.81 Nm Input Power Pi = VI Watts 2π NT Output Power Pm = ------------ Watts 60 Output Power Efficiency η % = -------------------- x 100% Input Power
  • 31. MODEL GRAPHS: Torque T (Nm) Speed N (rpm) Efficiency % Speed N (rpm) y y3 y2 y1 η N T x Torque T (Nm) Output Power (Watts) RESULT: Thus load test on DC shunt motor is conducted and its efficiency is determined.
  • 32. Ex.No.6 LOAD TEST ON DC COMPOUND MOTOR AIM: To conduct load test on DC compound motor and to find its efficiency. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20)A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostat 1250Ω , 0.8A Wire Wound 1 4 Tachometer (0-1500) rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. DC compound motor should be started and stopped under no load condition. 2. Field rheostat should be kept in the minimum position. 3. Brake drum should be cooled with water when it is under load.
  • 33. PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking the no load condition, and minimum field rheostat position, DPST switch is closed and starter resistance is gradually removed. 3. The motor is brought to its rated speed by adjusting the field rheostat. 4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no load condition. 5. The load is then added to the motor gradually and for each load, voltmeter, ammeter, spring balance readings and speed of the motor are noted. 6. The motor is then brought to no load condition and field rheostat to minimum position, then DPST switch is opened.
  • 35. TABULAR COLUMN: Spring Balance Output Input Voltage Current Speed Torque Reading Power Power Efficiency S.No. V I (S1∼ S2)Kg N T Pm Pi η % (Volts) (Amps) S1(Kg) S2(Kg) (rpm) (Nm) (Watts) (Watts)
  • 36. FORMULAE: Circumference R = ------------------- m 100 x2π Torque T = (S1 ∼ S2) x R x 9.81 Nm Input Power Pi = VI Watts 2π NT Output Power Pm = ------------ Watts 60 Output Power Efficiency η % = -------------------- x 100% Input Power
  • 37. MODEL GRAPHS: y3 y2 y1 Torque T (Nm) Speed N (rpm) Efficiency % η Speed N (rpm) N y T Output Power (Watts) x RESULT: Torque T (Nm) Thus load test on DC compound motor is conducted and its efficiency is determined.
  • 38. Ex.No.7 LOAD CHARACTERISTICS OF DC COMPOUND GENERATOR AIM: To obtain the load characteristics of DC Compound generator under cumulative and differential mode condition. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MC 1 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300)V MC 1 3 Rheostats 1200Ω , 0.8A Wire Wound 2 4 Loading Rheostat 5KW, 230V - 1 5 Tachometer (0-1500)rpm Digital 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The field rheostat of motor should be at minimum position. 2. The field rheostat of generator should be at maximum position. 3. No load should be connected to generator at the time of starting and stopping.
  • 39. PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field rheostat of generator. 4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted. 5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of DC shunt motor to minimum position, DPST switch is opened. 6. The connections of series field windings are reversed the above steps are repeated. 7. The values of voltage for the particular currents are compared and then the differential and cumulative compounded DC generator is concluded accordingly.
  • 41. TABULAR COLUMN: Cumulatively Compounded Differentially Compounded S.No. V (Volts) IL (Amps) V (Volts) IL (Amps) MODEL GRAPH: V (Volts) Cumulatively Compounded Differentially Compounded IL (Amps)
  • 42. RESULT: Thus load characteristics of DC compound generator under cumulative and differential mode condition are obtained
  • 43. Ex.No.8 LOAD TEST ON DC SERIES MOTOR AIM: To conduct load test on DC Series Motor and to find efficiency. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20)A MC 1 2 Voltmeter (0-300)V MC 1 (0-3000) 3 Tachometer Digital 1 rpm 4 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. The motor should be started and stopped with load 2. Brake drum should be cooled with water when it is under load.
  • 44. PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking the load condition, DPST switch is closed and starter resistance is gradually removed. 3. For various loads, Voltmeter, Ammeter readings, speed and spring balance readings are noted. 4. After bringing the load to initial position, DPST switch is opened.
  • 46. TABULAR COLUMN: Spring Balance Output Input Voltage Current Speed Torque Reading Power Power Efficiency S.No. V I (S1∼ S2)Kg N T Pm Pi η % (Volts) (Amps) S1(Kg) S2(Kg) (rpm) (Nm) (Watts) (Watts)
  • 47. FORMULAE: Circumference R = ------------------- m 100 x2π Torque T = (S1 ∼ S2) x R x 9.81 Nm Input Power Pi = VI Watts 2π NT Output Power Pm = ------------ Watts 60 Output Power Efficiency η % = -------------------- x 100% Input Power
  • 48. MODEL GRAPH: Torque T (Nm) Speed N (rpm) Efficiency % y3 y2 y1 T E N RESULT: Thus load test on DC series motor is conducted and its efficiency is determined. Output Power (Watts)
  • 49. Ex. No. 9 SWINBURNE’S TEST AIM: To conduct Swinburne’s test on DC machine to determine efficiency when working as generator and motor without actually loading the machine. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300) V MC 1 Wire 3 Rheostats 1250Ω , 0.8A 1 Wound 4 Tachometer (0-3000) rpm Digital 1 5 Resistive Load 5KW,230V - 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: The field rheostat should be in the minimum position at the time of starting and stopping the motor PROCEDURE:
  • 50. 1. Connections are made as per the circuit diagram. 2. After checking the minimum position of field rheostat, DPST switch is closed and starting resistance is gradually removed. 3. By adjusting the field rheostat, the machine is brought to its rated speed. 4. The armature current, field current and voltage readings are noted. 5. The field rheostat is then brought to minimum position DPST switch is opened.
  • 52. TABULAR COLUMNS: AS MOTOR: Total Output Input V IL Ia 2 Ia Ra Losses Efficiency S. No. Power Power (Volts) (Amps) (Amps) (Watts) W η % (Watts) (Watts) (Watts)
  • 53. AS GENERATOR: Total Output Input V I1 Ia Ia2Ra Efficiency S. No. Losses Power Power (Volts) (Amps) (Amps) (Watts) η % (Watts) (Watts) (Watts)
  • 54. TABULAR COLUMN: If Io V S.No. (Amps) (Amps) (Volts) DETERMINATION OF ARMATURE RESISTANCE: Fuse + - + A 27A (0-20)A D MC P S A1 T + 220V DC M V (0-300)V S MC Supply W - I T LOAD C 5 KW, 230V A2 H 27A - Fuse
  • 55. PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I TABULAR COLUMN: S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) FORMULAE:
  • 56. Hot Resistance Ra = 1.2 X R Ω Constant losses = VIo – Iao2 Ra watts Where Iao = (Io – If) Amps AS MOTOR: Load Current IL = _____ Amps (Assume 15%, 25%, 50%, 75% of rated current) Armature current Ia = IL – If Amps Copper loss = Ia2 Ra watts Total losses = Copper loss + Constant losses Input Power = VIL watts Output Power = Input Power – Total losses Output power Efficiency η % = ---------------------- X 100% Input Power AS GENERATOR: Load Current IL = _____ Amps (Assume 15%, 25%, 50%, 75% of rated current) Armature current Ia = IL + If Amps Copper loss = Ia2 Ra watts Total losses = Copper loss + Constant losses Output Power = VIL watts
  • 57. Input Power = Input Power +Total losses Output power Efficiency η % = ----------------------- X 100% Input Power MODEL GRAPH: As a Generator %η As a Motor OUTPUT POWER P0 (W) RESULT: Thus the efficiency of the D.C machine is predetermined by Swinburne’s test.
  • 58. Ex.No. 10 SPEED CONTROL OF DC SHUNT MOTOR AIM: To obtain speed control of DC shunt motor by a. Varying armature voltage with field current constant. b. Varying field current with armature voltage constant APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity 1 Ammeter (0-20) A MC 1 2 Voltmeter (0-300) V MC 1 1250Ω , 0.8A Wire 3 Rheostats Each 1 50Ω , 3.5A Wound 4 Tachometer (0-3000) rpm Digital 1 5 Connecting Wires 2.5sq.mm. Copper Few PRECAUTIONS: 1. Field Rheostat should be kept in the minimum resistance position at the time of starting and stopping the motor. 2. Armature Rheostat should be kept in the maximum resistance position at the time of starting and stopping the motor. PROCEDURE:
  • 59. 1. Connections are made as per the circuit diagram. 2. After checking the maximum position of armature rheostat and minimum position of field rheostat, DPST switch is closed (i) Armature Control: 1. Field current is fixed to various values and for each fixed value, by varying the armature rheostat, speed is noted for various voltages across the armature. (ii) Field Control: 1. Armature voltage is fixed to various values and for each fixed value, by adjusting the field rheostat, speed is noted for various field currents. 2. Bringing field rheostat to minimum position and armature rheostat to maximum position DPST switch is opened.
  • 61. TABULAR COLUMN: (i) Armature Voltage Control: If1 = If2 = If3 = Armature Speed Armature Speed Armature Speed S.No. Voltage N (rpm) Voltage N (rpm) Voltage N (rpm) Va ( Volts) Va ( Volts) Va ( Volts) (ii) Field Control: Va1 = Va2 = Va3 = Field Speed Field Speed Field Speed S.No. Current N (rpm) Current N (rpm) Current N (rpm) If (A) If (A) If (A) Speed N (rpm) Speed N (rpm) If1 If2 If3 MODEL GRAPHS: Va1 Va3 Va2 If (Amps) Va (Volts)
  • 62. RESULT: Thus the speed control of DC Shunt Motor is obtained using Armature and Field control methods. Ex.No. 11
  • 63. HOPKINSON’S TEST AIM: To conduct Hopkinson’s test on a pair of identical DC machines to pre-determine the efficiency of the machine as generator and as motor. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-1)A MC 1 1 Ammeter (0-20) A MC 2 (0-300) V MC 1 2 Voltmeter (0-600)V MC 1 Wire 3 Rheostats 1250Ω , 0.8A 2 Wound 4 Tachometer (0-3000) rpm Digital 1 5 Resistive Load 5KW,230V - 1 6 Connecting Wires 2.5sq.mm. Copper Few PRECATUIONS: 1. The field rheostat of the motor should be in the minimum position at the time of starting and stopping the machine. 2. The field rheostat of the generator should be in the maximum position at the time of starting and stopping the machine. 3. SPST switch should be kept open at the time of starting and stopping the machine.
  • 64. PROCEDURE: 1. Connections are made as per the circuit diagram. 2. After checking the minimum position of field rheostat of motor, maximum position of field rheostat of generator, opening of SPST switch, DPST switch is closed and starting resistance is gradually removed. 3. The motor is brought to its rated speed by adjusting the field rheostat of the motor. 4. The voltmeter V1 is made to read zero by adjusting field rheostat of generator and SPST switch is closed. 5. By adjusting field rheostats of motor and generator, various Ammeter readings, voltmeter readings are noted. 6. The rheostats and SPST switch are brought to their original positions and DPST switch is opened.
  • 66. TABULAR COLUMN: Motor Generator Total Stray Supply Armature Armature Stray Loss S.No. Voltage I1 I2 I3 I4 I1 + I2 Cu Loss Cu Loss losses Per M/c w/2 V(Volts) (Amps) (Amps) (Amps) (Amps) (Amps) W (watts) W(watts) W (watts) (watts)
  • 67. AS MOTOR: Motor Total Armature stray Output Input V I1 I2 I3 Field Loss Losses Efficiency S.No. Cu Loss losses Power Power (Volts) (Amps) (Amps) (Amps) (Watts) W η % W (Watts) /2(Watts) (Watts) (Watts) (Watts) AS GENERATOR: Motor Armature Total Stray Output Cu Loss Field Loss Losses Input Power Efficiency V I1 I2 losses Power S.No. W (Watts) W (Watts) η % (Volts) (Amps) (Amps) /2(Watts) (Watts) (Watts) (Watts)
  • 69. PROCEDURE: 1. Connections are made as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. Readings of Ammeter and Voltmeter are noted. 4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I TABULAR COLUMN: S.No. Voltage Current Armature Resistance V (Volts) I (Amps) Ra (Ohms) FORMULAE:
  • 70. Input Power = VI1 watts Motor armature cu loss = (I1+ I2)2 Ra watts Generator armature cu loss = I22 Ra watts Total Stray losses W = V I1 - (I1+I2)2 Ra + I22 Ra watts. Stray loss per machine = W/2 watts. AS MOTOR: Input Power = Armature input + Shunt field input = (I1+ I2) V + I3V = (I1+I2+I3) V Total Losses = Armature Cu loss + Field loss + stray loss = (I1 + I2)2 Ra + VI3 + W/2 watts Input power – Total Losses Efficiency η % = ------------------------------------- x 100% Input Power AS GENERATOR: Output Power = VI2 watts Total Losses = Armature Cu loss+ Field Loss + Stray loss = I22 Ra + VI4 + W/2 watts Output power Efficiency η % = -------------------------------------- x 100% Output Power+ Total Losses
  • 71. MODEL GRAPH: As a Generator %η As a Motor OUTPUT POWER P0 (W) RESULT: Thus Hopkinson’s test is conducted on a pair of identical DC machines the efficiency of the machine as generator and as motor are pre- determined Ex.No. 12
  • 72. LOAD TEST ON A SINGLE PHASE TRANSFORMER AIM: To conduct load test on single phase transformer and to find efficiency and percentage regulation. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-10)A MI 1 1 Ammeter (0-5) A MI 1 (0-150)V MI 1 2 Voltmeter (0-300) V MI 1 (300V, 5A) Upf 1 3 Wattmeter (150V, 5A) Upf 1 1φ , (0- 4 Auto Transformer - 1 260)V 5 Resistive Load 5KW, 230V - 1 6 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. Auto Transformer should be in minimum position. 2. The AC supply is given and removed from the transformer under no load condition. PROCEDURE: 1. Connections are made as per the circuit diagram.
  • 73. 2. After checking the no load condition, minimum position of auto transformer and DPST switch is closed. 3. Ammeter, Voltmeter and Wattmeter readings on both primary side and secondary side are noted. 4. The load is increased and for each load, Voltmeter, Ammeter and Wattmeter readings on both primary and secondary sides are noted. 5. Again no load condition is obtained and DPST switch is opened.
  • 75. TABULAR COLUMN: Primary Secondary Input Output Efficiency % S.No. Load V1 I1 W1 V2 I2 W2 Power Power η Regulation (Volts) (Amps) (Watts) (Volts) (Amps) (Watts) W1 x MF W2 x MF %
  • 76. FORMULAE: Output Power = W2 x Multiplication factor Input Power = W1 x Multiplication factor Output Power Efficiency η % = -------------------- x 100% Input Power VNL - VFL (Secondary) Regulation R % = ------------------------------ x 100% VNL MODEL GRAPHS: Efficiency η % Regulation R % η R RESULT: Thus the load test on single phase transformer is conducted. Output Power (Watts)
  • 77. Ex.No. 13 OPEN CIRCUIT & SHORT CIRCUIT TEST ON A SINGLE PHASE TRANSFORMER AIM: To predetermine the efficiency and regulation of a transformer by conducting open circuit test and short circuit test and to draw equivalent circuit. APPARATUS REQUIRED: S.No. Apparatus Range Type Quantity (0-2)A MI 1 1 Ammeter (0-5) A MI 1 2 Voltmeter (0-150)V MI 2 (150V, 5A) LPF 1 3 Wattmeter (150V, 5A) UPF 1 4 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. Auto Transformer should be in minimum voltage position at the time of closing & opening DPST Switch. PROCEDURE: OPEN CIRCUIT TEST:
  • 78. 1. Connections are made as per the circuit diagram. 2. After checking the minimum position of Autotransformer, DPST switch is closed. 3. Auto transformer variac is adjusted get the rated primary voltage. 4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted. 5. Auto transformer is again brought to minimum position and DPST switch is opened. SHORT CIRCUIT TEST: 1. Connections are made as per the circuit diagram. 2. After checking the minimum position of Autotransformer, DPST switch is closed. 3. Auto transformer variac is adjusted get the rated primary current. 4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted. 5. Auto transformer is again brought to minimum position and DPST switch is opened.
  • 81. TABULAR COLUMN: OPEN CIRCUIT TEST: Vo Io Wo (Volts) (Amps) (Watts) SHORT CIRCUIT TEST: Vsc Isc Wsc (Volts) (Amps) (Watts) FORMULAE: Core loss: Wo = VoIo cos φ o
  • 82. Wo Wo cos φ o = ------- φ o = cos-1 ------- Vo Io Vo Io Iω = Io cos φ o (Amps) Iµ = Io sin φ o (Amps) V0 V0 Wsc Ro = ------- Ω Xo = ------- Ω Ro2 = ------- Ω Iω Iµ Isc2 Vsc Xo2 = ( Zo2 - Ro22)1/2 Zo2 = ------- Ω Isc V2 R02 X02 K= ------- = 2 Ro1 = ------- Ω Xo1 = ------- Ω V1 K2 K2 Percentage Efficiency: for all loads and p.f. Output Power (X) x KVA rating x 1000 x cos φ Efficiency η % = -------------------- = ------------------------------------------------ Input Power Output power + losses
  • 83. (X) x KVA rating x 1000 x cos φ = ------------------------------------------------------------- (X) x KVA rating x 1000 x cos φ + Wo + X2Wsc Percentage Regulation: (X) x Isc (Ro2 cos φ ± Xo2sin φ ) x 100 = lagging + - = leading R% = -------------------------------------- V2 Where X is the load and it is 1 for full load, ½ for half load, ¾ load, ¼ load etc.. and the power factor is, upf, o.8 p.f lag and 0.8 p.f lead ISC R X o o1 EQUIVALENT CIRCUIT: o1 R I o L V O o A D R X o o ZL′ = ZL/K2 N
  • 84. MODEL GRAPHS: Efficiency η % % lagging Output power (Watts) Power factor % leading
  • 85. RESULT: Thus the efficiency and regulation of a transformer is predetermined by conducting open circuit test and short circuit test and the equivalent circuit is drawn.
  • 86. Ex.No. 14 SUMPNER’S TEST AIM : To predetermine the efficiency and regulation of a given single phase Transformer by conducting back-to-back test and also to find the parameters of the equivalent circuit. APPARATUS REQUIRED: S. No. Name of the Apparatus Range Type Quantity 1 Auto Transformer (0-270) V - 2 300 V, 10A LPF 1 2 Wattmeter 75 V, 5 A UPF 1 (0-2) A MI 1 3 Ammeter (0-20) A MI 1 (0-75) V MI 1 4 Voltmeter (0-150) V MI 1 5 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. Auto Transformer whose variac should be in zero position, before switching on the ac supply. 2. Transformer should be operated under rated values.
  • 87. PROCEDURE: 1. Connections are made as shown in the circuit diagram. 2. Rated voltage of 110V is adjusted to get in voltmeter by adjusting the variac of the Auto Transformer which would be in zero before switching on the supply at the primary side. 3. The readings of voltmeter, ammeter and wattmeter are noted on the primary side. 4. A voltmeter is connected across the secondary and with the secondary supply off i.e switch S is kept open. The voltmeter reading is noted. 5. If the reading of voltmeter reads higher voltage, the terminals of any one of secondary coil is interchanged in order that voltmeter reads zero. 6. The secondary is now switched on and SPST switch is closed with variac of auto transformer is zero. 7. After switching on the secondary the variac of transformer (Auto) is adjusted so that full load rated secondary current flows. 8. Then the readings of wattmeter, Ammeter and voltmeter are noted. 9. The Percentage Efficiency and percentage regulation are calculated and equivalent circuit is drawn.
  • 89. FORMULAE: W1 Core loss of each transformer Wo = ----- Watts 2 W2 Full load copper loss of each transformer Wc = ------ Watts. 2 Wo Io Wo = V1I1 Cos ϕ o ϕ o = Cos-1 --------- I1 = ---- A V1 I1 2 Iw = I1 CosΦ o Iμ = I1 CosΦ V2 = Vs/2 x A Ro = V1 / Iw Xo = V1 / Iμ Ro2 = Wc / I22 Zo2 = V2 / I2 Xo2 = √ Zo22 – Ro22 Copper loss at various loads = I22 Ro2
  • 90. PERCENTAGE REGULATION: 1. Upf : I2 / V (Ro2 CosΦ o) X 100 2. Lagging pf : I2 / V (Ro2 CosΦ o + Xo2SinΦ o) X 100 3. Leading pf : I2 / V (Ro2 CosΦ o - Xo2SinΦ o) X 100 Output Power (1) Upf : 3Kw (2) Pf : 3Kw CosΦ o Input Power = Output Power + Core loss + Cu loss Output power Efficiency η % = -------------------------- X 100% Input Power
  • 91. EQUIVALENT CIRCUIT: ISC R X o o1 o1 R I o L V O o A X D o R o N MODEL GRAPHS: Cos φ = 1 % Regulation % Efficiency Cos φ = 0.8 (Lead & Lag Cos φ = 1 Cos φ = 0.8 Lag Cos φ = 0.8 Lead Secondary Current (Amps) Secondary Current (Amps)
  • 92. RESULT: Thus the efficiency and regulation of a given single phase Transformer is carried out by conducting back-to-back test and the equivalent circuit parameters are found out.
  • 93. Ex.No. 15 SEPARATION OF NO LOAD LOSSES IN A SINGLE PHASE TRANSFORMER AIM: To separate the eddy current loss and hysteresis loss from the iron loss of single phase transformer. APPARATUS REQUIRED: S. No. Name of the Apparatus Range Type Quantity 1 Rheostat 1250Ω , 0.8A Wire Wound 2 2 Wattmeter 300 V, 5A LPF 1 3 Ammeter (0-2) A MC 1 4 Voltmeter (0-300) V MI 1 5 Connecting Wires 2.5sq.mm Copper Few PRECAUTIONS: 1. The motor field rheostat should be kept at minimum resistance position. 2. The alternator field rheostat should be kept at maximum resistance position. PROCEDURE: 1. Connections are given as per the circuit diagram. 2. Supply is given by closing the DPST switch. 3. The DC motor is started by using the 3 point starter and brought to rated speed by adjusting its field rheostat. 4. By varying the alternator filed rheostat gradually the rated primary voltage is applied to the transformer. 5. The frequency is varied by varying the motor field rheostat and the readings of frequency are noted and the speed is also measured by using the tachometer.
  • 94. 6. The above procedure is repeated for different frequencies and the readings are tabulated. 7. The motor is switched off by opening the DPST switch after bringing all the rheostats to the initial position.
  • 96. TABULAR COLUMN: S.No. Speed Frequency Voltage Wattmeter Iron loss Wi / f N (rpm) f (Hz) V (Volts) reading Wi (Watts) Joules Watts FORMULAE USED: 1. Frequency, f =(P*NS) / 120 in Hz P = No.of Poles & Ns = Synchronous speed in rpm. 2. Hysteresis Loss Wh = A * f in Watts A = Constant (obtained from graph) 3. Eddy Current Loss We = B * f2 in Watts B = Constant (slope of the tangent drawn to the curve) 4. Iron Loss Wi = Wh + We in Watts Wi / f = A + (B * f) Here the Constant A is distance from the origin to the point where the line cuts the Y- axis in the graph between W i / f and frequency f. The Constant B is Δ(Wi / f ) / Δf Wf y MODEL GRAPH: x A f
  • 97. RESULT: Thus separation of eddy current and hysteresis loss from the iron loss on a single-phase transformer is conducted.