This course gives you a fundamental understanding of the basic components that form a SMPS design and the installation, operation and troubleshooting of variable speed drives. You will understand how the selection of components affects the different performance parameters and operation of the SMPS. Typical practical applications of VSDs in process control and materials handling, such as those for pumping, ventilation, conveyers, compressors and hoists are covered in detail. The course also covers the basic setup of parameters, control wiring and safety precautions in installing a VSD.The various drive features such as operating modes, braking types, automatic restart and many others will be discussed in detail.

The course also covers the four basic requirements for a VSD to function properly with emphasis on typical controller faults, their causes and how they can be repaired. Even though the focus of the course is on the direct application of this technology, you will gain a thorough understanding of the problems that can be introduced by SMPSs and VSDs such as ripple, harmonics, electrostatic discharge and EMC/EMI problems.

NB: The course description of all EIT "Certificate" courses has been changed to "Professional Certificate of Competency". Some course brochures are not yet updated. The actual certificate received by successful students will include the new title.


At the end of this workshop you will be able to:

  • Demonstrate a sound understanding of how switch mode power supplies operate
  • Correctly select components and topology for a switch mode power supply
  • Evaluate the performance and stability of a switch mode power supply design
  • Demonstrate a sound understanding of how AC Variable Speed Drives (VSD's) work
  • Select the right VSD for a given application
  • Troubleshoot VSD's competently
  • Competently explain how flux-vector control works for drive applications
  • Understand squirrel cage induction motors
  • Identify the protection and control system requirements for VSD's
  • Understand the causes of motor burnout
  • Deal effectively with VSD harmonics and EMC/EMI problems

Course Outline

MODULE 1: Introduction to Power Electronic Circuits and Devices

  • Introduction
  • Definitions and basic principles
  • Power diodes and thyristors
  • Principles of commutation
  • Power electronic rectifiers
  • Power electronic inverters
  • Gate commutated converters
  • Gate controlled devices - GTO, FCT, GTR, FET, IGBT
  • Block diagram of power electronic circuits

MODULE 2: Introduction to Switch Mode Power Supplies

  • Basic principles of PSU circuits
  • Linear and SMPS comparison
  • Comparison of topologies
  • Non-isolated topologies
  • Isolated topologies
  • PWM controller review
  • Speed critical path
  • Choice of topology based on power supply Specifications

MODULE 3: Switch Mode Power Supply Design 1

  • Component selection and design criteria for input section
  • Input rectifiers
  • Input filter capacitors
  • High frequency transformer design
  • Basic transformer theory
  • Core material and geometry selection
  • Design of a power transformer for a PWM push-pull converter.
  • Losses and temperature rise
  • Winding techniques

MODULE 4: Switch Mode Power Supply Design 2

  • Output rectification and filtering
  • Power rectifier characteristics
  • Output power inductor design
  • Output filter capacitor design
  • Heat sinking
  • The thermal equation
  • Selecting a heatsink
  • Custom heatsink

MODULE 5: Switch Mode Power Control and Stability

  • Transfer functions
  • Criteria for stability
  • Control to output gain
  • Design compensation network
  • Control stability measurements

MODULE 6: Introduction to Variable Speed Drives

  • Need for variable speed drives
  • Fundamental principles of speed control
  • Efficiency, torque, inertia, horsepower/power factor
  • Torque-speed curves
  • How the motor produces torque
  • Types of variable speed drives

MODULE 7: 3-Phase Induction Motors

  • Basic construction and physical
  • configuration
  • Principles of operation and performance
  • Equivalent circuit and fundamental equations
  • Starting, acceleration, running and stopping
  • Power, torque and thermal rating

MODULE 8: Protection of Motors

  • AC frequency converter protection
  • Fault diagnostics
  • Electric motor protection
  • Thermal overload protection – current sensors
  • Thermal overload protection – direct Temperature

MODULE 9: Control System for AC Variable Speed Drives

  • Overall control system
  • Power supply to the control system
  • DC bus charging system
  • VSD control loops (open-loop, closedloop)
  • Vector control and its applications
  • Current feedback in AC variable speed drives
  • Speed feedback from the motor

MODULE 10: Selection of AC Converters for Variable Speed Drives Applications

  • Basic selection procedure
  • Load ability of converter fed induction motors
  • Operation in the constant power region
  • Nature of the machine load
  • Starting and stopping VSDs (motor braking)
  • How to calculate acceleration torques and times
  • How to select the correct motor and converter for pump and fan loads
  • How to select the correct motor and converter for constant torque loads, such as conveyors
  • Summary of the selection procedure

MODULE 11: Electromagnetic Compatibility (EMC)

  • Sources of electromagnetic interference
  • Noise specifications and RFI sources in SMPS
  • Filters for RFI suppression
  • Harmonics on the power supply side of AC converters
  • Effect of harmonic distortion on other connected equipment
  • Methods of reducing the effect of supply side harmonics

MODULE 12: Installation and Fault Finding Techniques

  • Troubleshooting of SMPS
  • General installation and environmental requirements
  • Power supply connections and earthing
  • Where to install the contactors in the power circuit
  • Installing AC converters into metal enclosures


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