Three phase delta connection
- 1. Three Phase Delta Connection:- • What is Delta Connection (Δ)? Delta or Mesh Connection (Δ) System is also known as Three Phase Three Wire System (3-Phase 3 Wire) and it is the most preferred system for AC power transmission while for distribution, Star connection is generally used. In Delta (also denoted by Δ) system of interconnection, the starting ends of the three phases or coils are connected to the finishing ends of the coil. Or the starting end of the first coil is connected to the finishing end of the second coil and so on (for all three coils) and it looks like a closed mesh or circuit. In more clear words, all three coils are connected in series to form a close mesh or circuit. Three wires are taken out from three junctions and the all outgoing currents from junction assumed to be positive. In Delta connection, the three windings interconnection looks like a short circuit, but this is not true, if the system is balanced, then the value of the algebraic sum of all voltages around the mesh is zero in Delta connection. When a terminal is open in Δ, then there is no chance of flowing currents with basic frequency around the closed mesh.
- 2. • NO NEUTRAL :- A true delta configuration has no neutral. It is a 3-phase, ungrounded power system where connection from any two nodes is the same voltage. It is possible tohave a delta system with a neutral, which is typically done by center-tapping one of the three transformers and pulling your neutral from ther • WHY DELTA CONNECTION IS USED?:- The phase voltage is lower than line voltage in star connection, so the motors or drives connected in star connection runs at lower speed as compared to delta connection. Star Connection is prefferable in transmission system as the voltage insulation required is less. Delta connection is used in Distribution system Delta Connections are often used in applications which require high starting torque. • DELTA ADVANTAGES - efficient - more torque - simple motor design - protection is simple and less costly - construction cost is cheaper (3 conductors instead of 4) - heavy duty applications - used in rotatory conveyors - less current per winding for the same power output - major applications in power generation, transmission and distribution - the transformer secondary provides all the 3 phases (if one is lost, you still have 2) DELTA DISADVANTAGES - no common neutral point - detecting earth ground faults is difficult - low voltage connection
- 3. • Voltage, Current and Power Values in Delta Connection (Δ) Line current, Line Voltage, Phase Current, Phase Voltages and Power in three phase Delta AC system. 1. Line Voltages (VL) and Phase Voltages (VPh) in Delta Connection:- In fig 2 that there is only one phase winding between two terminals (i.e. there is one phase winding between two wires). Therefore, in Delta Connection, the voltage between (any pair of) two lines is equal to the phase voltage of the phase winding which is connected between two lines. Since the phase sequence is R → Y → B, therefore, the direction of voltage from R phase towards Y phase is positive (+), and the voltage of R phase is leading by 120°from Y phase voltage. Likewise, the voltage of Y phase is leading by 120° from the phase voltage of B and its direction is positive from Y towards B. If the line voltage between; • Line 1 and Line 2 = VRY • Line 2 and Line 3 = VYB • Line 3 and Line 1 = VBR Then, we see that VRY leads VYB by 120° and VYB leads VBR by 120°. Let’s suppose, VRY = VYB = VBR = VL …………… (Line Voltage) Then VL = VPH I.e. in Delta connection, the Line Voltage is equal to the Phase Voltage.
- 4. 2.Line Currents (IL) and Phase Currents (IPh) in Delta Connection:- It will be noted from the below (fig-2) that the total current of each Line is equal to the vector difference between two phase currents in Delta connection flowing through that line. i.e.; • Current in Line 1= I1 = IR – IB • Current in Line 2 =I2 = IY – IR • Current in Line 3 =I3 = IB – IY {Vector Difference} The current of Line 1 can be found by determining the vector difference between IR and IB and we can do that by increasing the IB Vector in reverse, so that, IR and IB makes a parallelogram. The diagonal of that parallelogram shows the vector difference of IR and IB which is equal to current in Line 1= I1. Moreover, by reversing the vector of IB, it may indicate as (-IB), therefore, the angle between IRand -IB (IB, when reversed = -IB) is 60°. If, IR = IY = IB = IPH …. The phase currents Then; The current flowing in Line 1 would be; IL or I1 = 2 x IPHx Cos (60°/2)
- 5. = 2 x IPH x Cos 30° = 2 x IPH x (√3/2) …… Since Cos 30° = √3/2 IL= √3 IPH i.e. In Delta Connection, The Line current is √3 times of Phase Current. Similarly, we can find the reaming two Line currents as same as above. i.e., I2 = IY – IR … Vector Difference = √3 IPH I3 = IB – IY … Vector difference = √3 IPH As, all the Line current are equal in magnitude i.e. I1 = I2 = I3 = IL Hence IL = √3 IPH • Power in Delta Connection We know that the power of each phase; Power / Phase = VPH x IPH x CosФ And the total power of three phases; Total Power = P = 3 x VPH x IPH x CosФ ….. (1) We know that the values of Phase Current and Phase Voltage in Delta Connection; IPH = IL /√3 ….. (From IL = √3 IPH) VPH = VL Putting these values in power eq……. (1) P = 3 x VL x ( IL/√3) x CosФ …… (IPH = IL / /√3) P = √3 x√3 x VL x ( IL/√3) x CosФ …{ 3 = √3x√3 } P = √3 x VLx ILx CosФ … Hence proved; Power in Delta Connection, P = 3 x VPH x IPH x CosФ …. or P = √3 x VL x IL x CosФ
- 6. • CONCLUSION :- 1. After working or performing this project we get the detailed knoweledge about the delta connection . 2. We also get the knowledge about following points:- • Where we have to use the delta connection circuit. • What are the applications of delta circuit in the industry . • Why no neutral is there in the delta connection . • What is line voltage and phase voltage. • what is line current and phase current. • Relation between the line voltage ,phase voltage and line current and the phase current. • Power in the delta connection.