Active front end drive
- 1. M A H E S H K U M A R S M S 2 E L E C T R I C A L B S M 0 5 6 6 ACTIVE FRONT END DRIVE OF KONECRANE
- 2. VARIABLE VOLTAGE VARIABLE FREQUENCY DRIVE (VVVF) • VVVF drive is a power electronics based device which converts a basic fixed frequency, fixed voltage sine wave power (line power) to a variable frequency, variable output voltage which is used to control speed of induction motor. • It regulates the speed of a three phase induction motor by controlling the frequency and voltage of the power supplied to the motor. Ns = 120*f P • Since the number of pole is constant the speed Ns can be varied by continuously changing frequency.
- 3. • Any reduction in the supply frequency without a change in the terminal voltage causes an increase in the air gap flux which will cause magnetic saturation of motor. Also the torque capability of motor is decreased. • Hence while controlling a motor with the help of VVVF Drive we always keep the V/f ratio constant.
- 4. • The mains AC supply voltage is converted into a DC voltage and current through a rectifier. The DC voltage and current are filtered to smooth out the peaks before being fed into an inverter, where they are converted into a variable AC voltage and frequency. • The output voltage is controlled so that the ratio between voltage and frequency remains constant to avoid over-fluxing the motor. AC DRIVE SYSTEM
- 5. PULSE WIDTH MODULATION: • Pulse-width modulation (PWM) is a modulation technique used to vary the width of the pulse. • PWM signals are pulse trains with fixed frequency and magnitude and variable pulse width. • Continuous change of the pulse width results in a continuous change of the average value of the voltage.
- 6. ACTIVE FRONT END DRIVE The diode rectifier does not allow power flow from the DC link to the supply side ,so diode rectifier is replaced with an IGBT rectifier. The 6-pulse PWM bridge converter with IGBTs is shown in figure and is electrically similar to a normal PWM inverter. As with the PWM inverter, it can transfer electrical energy in either direction, depending on the switching sequence of the IGBTs.
- 7. ELECTRIC MOTOR – SPEED / TORQUE Quadrant I -- Driving or motoring, forward accelerating quadrant with positive speed and torque Quadrant II -- Generating or braking, forward braking- decelerating quadrant with positive speed and negative torque Quadrant III - Driving or motoring, reverse accelerating quadrant with negative speed and torque Quadrant IV - Generating or braking, reverse braking decelerating quadrant with negative speed and positive torque.
- 9. MOTOR ARRANGEMENT IN CRANE
- 10. MOTOR & DRIVE DETAIL
- 11. OVERVIEW • The DynA Vector II family is a complete control system for every crane motion providing dynamic and safe crane operation. • The family includes DynAC Vector II (D2C) for travelling, • DynAHoist Vector II (D2H) for hoisting and DynAReg Vector II (D2R) for regenerative network braking. • Their robust construction ensures excellent tolerance to extreme ambient conditions.
- 12. • The three phase utility interface of variable speed D2C and D2H AC-drives can be improved effectively by applying the D2R PWM-rectifier. The PWM-rectifier costs more than a simple diode rectifier, but it provides numerous benefits. Bidirectional Power Flow • The regenerative network braking enables very efficient energy optimization. The crane operation requires frequent starting and stopping. During each braking period as well as during load lowering, the generated energy must be either wasted by resistor braking or, specially in process duty with high power ratings, fed back to the supply line with the D2R. Low Line Current Distortion • The line current distortion of a six pulse diode rectifier is seldom below 40 %. Distortion levels exceeding 100 % are not unusual. By included LCL line filter the total harmonic distortion of D2R can be typically decreased by a factor of 10. • Unity Power Factor • Basically, the displacement factor of a diode rectifier is good, but due to the line current harmonics the actual ratio of active and apparent power is not good. The D2R can be controlled to unity power factor with sinusoidal line currents, thus reducing the supply fuse sizes.
- 13. • Insensitivity To Line Voltage Variations • Due to the closed loop DC-voltage control, the dc-link becomes insensitive to line voltage variations. Voltage dips, for example, do not affect the operation provided that the maximum current is not exceeded. With the D2R the need to oversize the equipment is minimal - even for weak networks • Controllable DC-voltage • The DC-link voltage is controlled by the D2R, resulting to a constant voltage with a level higher than with a diode rectifier. The actual voltage level can be chosen almost independently from the line voltage - typically the level is adjusted 10 ... 25 % above that achieved with a diode rectifier. • Latest Technology • The D2R PWM-rectifier is of a state-of-the-art design with IGBT-switches. The space vector based control strategy provides extremely fast response and excellent accuracy. • Spare Parts • As the D2R belongs to the same family with D2C and D2H, a great number of common components minimize the spare part inventory and simplify the maintenance procedures.
- 14. TECHNICAL DATA
- 15. TYPE MARK CODING
- 16. PRE CHARGING CIRCUIT • The Active Front End unit requires an external pre-charging circuit. The purpose of the pre charging unit is to charge the voltage in the intermediate circuit to a level sufficient for connecting the Active Front End unit to the mains. • The Active Front End unit must not be connected to mains without pre- charging.
- 17. CONTROL UNIT The control unit of Vacon NX Active Front End consists of the control board and option boards (see Figure 49 and Figure 50) connected to the five slot connectors (A to E) on the control board.
- 18. CONNECTIONS ON CONTROL BOARD • Basic I/O board (Slot A) It has two board levels, one for electronics level signals (terminals 1-10) and one for control voltage signals (42- 240 Vac). • Relay / Thermistor board (Slot B) • SSU Speed Supervision board (Slot C) • I/O Extension board (Slot D) • Relay Extension board (Slot E) • Profibus board (Slot E) The board has the 9-pin female D-connector for the Profibus cable.
- 19. INVERTER • Inverter includes Power supply unit (PSU) and Control unit (CSU), which are separate parts , connected through fiber optic cable. • PSU includes supply, brake resistor and motor connections. IGBTs are placed to PSU. Microprocessors and ASIC are placed to CSU. Same CSU can be used in every power class.
- 20. CLOSED LOOP VECTOR CONTROL
- 21. ACTIVE FRONT END UNIT BLOCK DIAGRAM
- 22. Thank you!