Course willrevise the basics of transformers, generators, induction motors and synchronous motors. The need of speed control befits of VSD technology and their components will be discussed. Moderns VSDs driven by multi-level inverters will be presented. Closed loop control of VSDs, PID tuning, power quality issues, dv/dt, pwm waveforms, common mode voltage and their mitigation techniques will be discussed. Grounding, isolation, safety precautions to be taken, international standards and practices, protection of MV VFDs, switchgear and maintenance, trouble shooting of VSDs will be discussed.
At the end of this course, participants should be able to:
Able to draft the general specifications for a VFD system
Module 1: Introduction to motors, type soft motors, induction motors, applications
Module 2:Motor characteristics, Motor parameters, LV and MV motors (induction motor and synchronous motor) , MV motor specifications, data sheets. Open-end winding induction motors. Calculation of motor parameters form the name plate data, motor class, and protection. International standards on motors.
Module 3: Starting of motors, need for starters, speed control of motor -constant flux and flux weakening operation. Induction motor as induction generator. Calculation of motor efficiency,
Module 4: Introduction to variable speed drives, Components of a drive. Selection of drive, Computing the torque, sped and voltage for given load, load character tics, types of load. Connecting load to motor shaft, calculation of motor shaft torque, selection of gears, gear losses, output power at load end.
Module 5: AC to DC converters –operation, circuits, illustration and demonstration of a three phase AC to DC converter.
Module 6:DC to AC Inverter Principle of operation, CSI and VSI . PWM techniques
Module 7: Multi –level inverters, operation and improvement on motor voltages. Input side PWM rectifiers and advantages on power quality. Regenerative breaking using breaking resistor and regeneration of power using input side PWM rectifier
Module 8: Variable speed drive- Stator voltage control, constant v/f control, vector control and direct torque control of induction motor, rotor side control using inverters, control of open-end winding induction motors
Module 9: Variable speed drive- constant v/f control, vector control and direct torque control of synchronous motor
Module10: dv/dt, common mode voltage, PWM nature of voltages, its impact on motor, long cable operation with PWM signals, common mode voltages, bearing leakage currents, bearing failures, mitigation techniques, filters at the output of inverter, selection and design.
Module11: Power quality issues, impact of VSDs/VFDs on power system, harmonics, power factor issues, mitigation techniques, input side filters, line reactors, input side transformers, derating of transformers
Module 12: HSE requirements, precautions, fault identification, fault isolation and troubleshooting, using instruments for VSDs
Chapter 11: International standards on MV, MV-VFDs, Harmonics, power factor correction circuits.
Chapter 12: MV switchgear principles and standards, protection circuits
Chapter 13: Grounding of inverter driven motors, impact of PWM voltages and high dv/dt on motor insulation
Chapter 14: Condition monitoring of MV motors: Stator faults, rotor faults, air gap irregularities, bearings faults
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