Troubleshooting, Maintenance and Protection of AC Electrical Motors and Drives

Introduction

The program will introduce delegates to the different types of motors and drives and their associated terminology. The application of the different types of motors will be discussed along with their suitability for different operational duties. The operation, troubleshooting, and maintenance will be dealt with in-depth. It is estimated that electrical drives and other rotating equipment consume about 50% of the total electrical energy consumed in the world today. The cost of maintaining electrical motors can be a significant amount in the budget item of the manufacturing and mining industries. This workshop gives you a thorough understanding of electrical motor's working, maintenance, and failure modes and gives you the tools to maintain and troubleshoot electrical motors. You will gain valuable insight into the selection of the protection necessary to ensure your motors are protected against fault conditions, so as to ensure reliability and long life. You will gain a fundamental understanding of the installation, operation, and troubleshooting of electric motors. Typical applications of electric motors in mining, manufacturing, materials handling, and process control are covered in detail. You will learn the basic steps in specifying, installing, wiring, and commissioning motors. The concluding section of the course gives you the fundamental tools in troubleshooting motors confidently and effectively.

Objectives

The objectives of this course:-

• Have an understanding of the different types of motors and drives.
• Be able to operate motors as close as possible to the design efficiency.
• Will be able to monitor efficiency, availability, and reliability.
• Have learned about selection, operation, and maintenance strategies.
• Be able to troubleshoot motor and drive problems.
• To present the operation and construction of AC electric 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 discuss maintenance procedures both for motors and drives following well-established industrial procedures as outlined in standards.
• To familiarize with troubleshooting methods for both motors and drives following methodologies that have been developed by manufacturers in order to reduce downturn time dramatically.
• To become familiar with how to utilize single-line drawings and other documentation to successfully perform commissioning, maintenance and troubleshooting.
• To analyze case studies and learn from such experience.
• Specify, select and install motors
• Specify protection requirements for motors
• Specify speed control requirements for motors
• Install and commission motors
• Fix faults on motors
• Interpret motor performance curves
• Interface control circuits of motors with PLCs/DCSs
• Reduce downtime on electrical motors
• Improve plant safety
• Improve plant throughput
• Reduce spares usage and requirements

Training Methodology

This is an interactive course. There will be open question and answer sessions, regular group exercises and activities, videos, case studies, and presentations on best practice. Participants will have the opportunity to share with the facilitator and other participants on what works well and not so well for them, as well as work on issues from their own organizations. The online course is conducted online using MS-Teams/ClickMeeting.

Who Should Attend?

Anyone associated with the use of electrical motors in the industrial or automation environment. The workshop will also benefit those working in system design as well as site commissioning, maintenance, and troubleshooting. Typical personnel who would benefit are:

• Plant Engineers
• Instrument Technicians
• Operations Personnel
• Electrical Maintenance Technicians & Supervisors
• Instrument and Control Engineers
• Process Control Engineers
• Electrical and mechanical engineers.
• Technicians and plant operations and maintenance personnel.
• Supervisors, team leaders, and professionals in maintenance engineering departments.
• Anyone who wishes to update their knowledge on one of the most important equipment combinations, i.e. motor/drive, and how to get the best of their trouble-free operation in the plant if possible.
• Mechanical Engineers
• Service Technicians
• Maintenance Personnel

Course Outline

Day 1: Introduction

• An Introduction to Motor Types
• Induction, DC, servo, synchronous, linear, etc.
• Induction Motors
• Introduction to AC induction motors and their construction, rotor slip and principles of operation, equivalent circuit, torque-speed characteristics, motoring and regenerative region of operation
• Starting of induction motors and associated techniques
• Speed control methods of induction motors
• Characteristics of motors, enclosures, and cooling methods, application data, design characteristics, insulation of AC motors
• DC Motors
• Introduction to DC motors and their construction, principles of operation, and torque-speed characteristics.
• Conversion of AC to DC
• Motor Selection
• Torque/speed, ripple, peak
• Acceleration
• Load/power density
• Thermal capacity
• Efficiency

Day 2: Motor Diagnostics & Troubleshooting

• Identification of damage mechanisms & remediation
• Damage Mechanisms
• Dynamic defects - imbalance, misalignment, looseness
• Insulation degradation
• Stator faults
• Rotor faults
• Controller faults
• Monitoring Techniques
• Vibration analysis
• Thermography
• Motor current analysis
• Motor resistance/capacitance analysis
• Troubleshooting
• Motor Control
• Drives, protection systems, and controllers
• Drives
• Induction motor starters & drive panel instrumentation & control
• DC drives, protection & control
• Protection Systems
• Short circuit
• Ground
• Single phasing
• Rotor Lock, etc.

Day 3: Variable Speed 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, reg generation
• 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, 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

Day 4: 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.

Day 5: 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.