AC Electrical Motor & Drives Troubleshooting, Maintenance & Protection

The course covers all topics relating to both AC motors and their drives. AC motors represent industry's workhorse in all applications. It is no exaggeration to suggest that more than half of the energy consumed worldwide is converted by AC motors into work and these are controlled by drives.

Understanding maintenance and troubleshooting procedures of such vital industrial equipment means that reduced downtime and increased productivity for the company. The protection a requirement along with their function and integration with the overall system ensures that such expensive apparatus is well guarded against failures which further offer safety for operations personnel as well.

This course will feature

• Understanding types of AC motors and their starting methods
• Principle of operation of variable speed drives
• Identification of the various types of variable speed drive
• Trouble shooting and maintenance of variable speed drives
• Protection of motors and drives

Course Objectives

By the end of this course, participants will be able to:

• Understand the various types of AC motors and starters
• Determine the components and operations of variable speed drives
• Explain the different types of variable speed drives
• Analyze the common faults in a variable speed drive
• Design the protection requirements for motors and drives

Who Should Attend?

This course will benefit all levels of professional in an electrical installation. It will enable them to understand operation, maintenance and troubleshooting of AC motors and drives

This course is suitable to a wide range of technical professionals but will greatly benefit:

• Electricians
• Electrical supervisors
• Plant electricians
• Operations & maintenance engineers, supervisors & technicians
• Maintenance technicians

Course Outline

Day One
AC Motors

• Discussion - Goals
• Introduction to magnetic, 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.

Day Two
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.

Day Three
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.

Day Four
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.

Day Five
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.
• Case studies, selection and design of systems and their protection.

Course Methodology

A variety of methodologies will be used during the course that includes:

• (30%) Based on Case Studies
• (30%) Techniques
• (30%) Role Play
• (10%) Concepts
• Pre-test and Post-test
• Variety of Learning Methods
• Lectures
• Case Studies and Self Questionaires
• Group Work
• Discussion
• Presentation

Course Fees

This rate includes participant’s manual, Hand-Outs, buffet lunch, coffee/tea on arrival, morning & afternoon of each day.

Course Timings

Daily Course Timings
08:00 - 08:20       Morning Coffee / Tea
08:20 - 10:00       First Session
10:00 - 10:20       Coffee / Tea / Snacks
10:20 - 12:20       Second Session
12:20 - 13:30       Lunch Break & Prayer Break
13:30 - 15:00       Last Session