Variable Speed-Drive Troubleshooting

What are the Goals?

The objectives of the training course are:

• To define the operation and construction of AC electrical motors and the electrical drives based on modern state-of-the-art inverter technology, and their characteristics that need to be matched with those of loads
• To review maintenance procedures both for motors and drives following well-established industrial procedures as outlined in standards
• To illustrate with troubleshooting methods for both motors and drives following methodologies that have been developed by manufacturers in order to reduce downturn time dramatically
• To analyse and familiarize on how to utilize single-line drawings and other documentation to successful perform commissioning, maintenance and troubleshooting
• To share case studies and learn from such experience

Who is this Training Course for?

Variable speed drive and troubleshooting is intended for:

• Electrical engineers
• Technicians and plant operations and maintenance professionals
• Team leaders and professionals in maintenance engineering departments
• Anyone who wishes to update their knowledge on one of the most important equipment combination, i.e. motor/drive and how to get the best of their trouble-free operation in the plant if possible

Daily Agenda

Day One: AC Motors

• Fundamentals of rotating machines theory, rotor types, rotor slip and principles of operation, equivalent circuit, torque-speed characteristics
• Three phase induction motors types, construction, principle of operation, characteristics and applications
• Three phase synchronous motors construction and characteristics
• Starting of induction motors and associated techniques, accelerating and soft starters
• Speed control requirements of AC motors and load matching
• Medium voltage three phase induction motors

Day Two: Drives-Introduction

• Variable speed drive motors verses general purpose motors, VSD selection
• Reasons and advantages of variable speed drives, DC drive and AC drive comparisons, VFD curves and tests
• Variable speed drives basic theory, voltage source inverter, current course inverter and pulse width modulation
• Variable speed drives disadvantages, harmonics mitigation
• Choosing the best variable frequency drives and installation considerations
• Variable speed drives parameter programming and applications

Day Three: Drives Fundamentals

• 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
• Operations of DC link energy and inverters, regeneration or dynamic slowdown, dynamic breaking, plugging
• 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, insulation voltage stress, electromagnetic interferences (EMI), EMI filtering, VFD shielded cables

Day Four: Troubleshooting and Maintenance of Drives

• Variable speed drives generic troubleshooting techniques
• Variable speed drives modes of operations, converter failures, common failure modes
• Variable speed drives motor bearing maintenance
• Testing and identification of failed thyristor and diode
• Test instruments and VSD analysers
• 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, Numerical relays for motor and drives protection
• VFD motor problem areas, voltage on shaft, shaft induced current
• Variable speed drives modular design and maintenance
• Methods of preventing bearing failures in VSDs
• Protection of inverters and electronic converters driving motors
• Medium voltage variable speed drives and protection