Electrical Motors & Drives: Troubleshooting, Maintenance & Protection

This AC Electrical Motors and Drives: Troubleshooting, Maintenance and Protection training will teach the course content as outlined.

Programme Outline

AC Motor

• Introduction to magnetics, excitation and the generation of back emf.
• Fundamentals of rotating machines theory, AC motors and their construction, rotor slip and principles of operation, equivalent circuit, torque-speed characteristics, motoring and regenerative region of operation, efficiency, inertia, horsepower, power factor. 
• Single-phase and three-phase AC motors, types of single-phase motors, split-phase and capacitor. 
• Starting of induction motors and associated techniques, accelerating. 
• Speed control requirements of AC motors and load matching. 

Drives

• Basic principles of AC Variable-Speed Drives (VSD's), constant torque region, constant power (extended speed) region, four quadrant operation. 
• Power semiconductors, diode, thyristor (SCR), IGBT, MOSFET, GTO and others. 
• Inverters, voltage-source and current-source, pulse width modulated (PWM) inverters. 
• Two-level pulse width modulated inverter, DC link energy and capacitor sizing, regeneration or dynamic slowdown, dynamic breaking, regeneration. 
• PWM waveforms and analysis, effects of PWM on motor bearings and insulation and life expectancy, volts/ Hertz control, start up and operation, dynamics, PWM rectifier inverter systems. 
• Switching transients, harmonics and power factor.

• AC drive line power factor, effect of AC input on drive operation, switching transients, insulation voltage stress, motor winding voltage distribution, radiated and conducted electromagnetic interferences (EMI), EMI filtering. 
• Troubleshooting and Maintenance of Motors 
• Characteristics of motors, enclosures and cooling methods, application data, design characteristics, insulation of AC motors. 
• Failures in three-phase stator windings, predictive maintenance, motor troubleshooting, diagnostic testing for motors. 

• Troubleshooting and maintenance of AC motors, routine care, dirt and corrosion, lubrication, heat, noise and vibration, insulation. 
• Slow acceleration or refusal to starting of an AC motor, overheating and noise making of the motor, running of bearings at high temperature or making noise. 
• Standards and testing. 

Troubleshooting and Maintenance of Drives

• Converter failures, common failure modes, fault current limit, device explosion rating, device application, thyristor failures and testing, identification of failed thyristor and diode, testing of thyristor and diode. 
• Reversing circuits for single-phase and three-phase AC motors, finding open and short-circuit, detection of AC motor symptoms. 
• Preventative maintenance, approaches, guidelines and scheduling, checking, dynamic and static inspections, detecting phase unbalances, loss of phases, and phase reversal. 
• Protection of Motors and Drives 
• Protection of AC motors, requirements, overload protection, currents during starting and stalled point, operation of motors under three-phase unbalanced power supply, motor de-rating due to unbalanced currents, stator and rotor protection, single-phase over-current relays, phase unbalance relays, faults in stator and rotor windings, earth faults, phase-to-phase faults, modern relay design and applications, protection targeting AC synchronous motors, over-voltage and under-frequency protection. 
• Fuses, circuit breakers, magnetic and thermal, overload, eutectic, bimetal and solid-state, others. 
• Motor protection curves, back-up protection.
• Protection of inverters and electronic converters driving motors.