Switched Reluctance Motor (SRM) drives have some unique features: phase independence and high reliability, low cost of manufacture, unidirectional current requirement simplifying the converter arrangement, availability of a large number of converter arrangements, no shoot-through fault hazard and inherent suitability for high speed operation. Because of these features, they are presently considered for high volume, low cost applications and also in special applications such as in aircraft motor generator system.

The demand for research and development engineers is increasing to find ways to realize drive systems with and without position sensors and to provide auto-tuning with the process/load. Further, the end users of variable speed drives need to be knowledgeable about the latest developments in this field, its current status and its future direction to enable them to plan new capital investments wisely and to have the latest technology incorporated in their plans for plant modernization.

This course is intended to address these requirements for engineers specializing in the drives technology and end users in many aspects of this technology. A state-of-art coverage of the subject matter based on research publications is developed in this short-term course.

Course is $1695 per participant.

  • Principle of operation of the SRM drive is introduced.
  • A review of various type of SRMs is given.
  • The equivalent circuit of the SRM is derived to enhance a conceptual understanding of its operation.

The key to computing the performance characteristics of the SRM is to have their flux linkage vs. current vs. rotor position relationships. It is analytically derived in terms of the machine dimensions, excitation current, rotor position and magnetic material characteristics to understand the impact of each of these variables and constants on the three dimensional relationships. Even though finite element analysis provides the same results with a little more accuracy, emphasis is placed on the analytical relationships as they contribute to the understanding of the underlying phenomenon.

  • With the three dimensional relationship, the machine design is introduced.
  • To facilitate the use of knowledge base form other machine design, a design procedure based on the output equation is chosen.
  • A systematic analysis of losses, and impact of machine pole arc to pole pitch ratio, pole tapering, and current rise and fall times on machine torque are derived.
  • Based on these and other criteria, the machine dimensions for stator poles, rotor poles, number of turns in the coil and its wire size, air gap and its impact, back iron thickness are derived.
  • Thus the machine design by analytic means is achieved.
  • A procedure for computing the steady state and dynamic torque is developed.
  • Linear SRM drives and their various configurations, basic operation, elementary guidelines for design and its implementation for traction, elevator and maglev applications are presented.

The converter is an integral part of the SRM and therefore a review of useful converter arrangements and their functioning are systematically developed. Switching strategies for these converters are discussed. Design information is developed for the converters that are predominantly considered for emerging applications. Wherever appropriate, some comparison among them is drawn.

Control strategies form the heart of the drive systems and have a critical impact on the performance of the drive system. Torque and speed controls are implemented mostly with the simple proportional integral (PI) controllers and a design procedure is developed for them. As the torque ripple is of significant concern in applications, control methods to reduce it are presented. Modern control methods using artificial neural networks and fuzzy controllers are discussed. The modeling for the simulation of the integrated drive system is developed and illustrated with a number of operational cases.

Position and current sensorless operation of the SRMs is of immense interest to industry. A review of sensor based feedback measurements and their estimation without using a sensor or using low cost sensors as in the case of currents is given. Particular emphasis is placed on the various methods of position estimation and their performance in a drive system.

Acoustic noise is of major concern in applications. The sources of noise, their mitigation methods and current research knowledge on the SRM acoustic noise are put in proper perspective. Some helpful design measures are summarized for practice.

  • Some applications of SRM drives will be discussed.
Photo of R. Krishnan, Ph.D.

Dr. Krishnan Ramu (writes under the name of R. Krishnan):  Professor Emeritus of electrical and computer engineering at Virginia Polytechnic Institute and State University. His research interests are in electric motor drives, electric machines, power electronics.

Books: (a) Author of: (i)  Electric Motor Drives (also translated into  Chinese, Greek) , (ii) Switched Reluctance Motor Drives, (iii) Permanent Magnet Synchronous and Brushless DC Motor Drives (translated into Chinese also). (b) coauthored one book (iv) Control in Power Electronics.

Publications: 170+ technical papers. Patents: 30 patents (27 US and 3 Japanese) and  6+ pending.

Awards:  (i) IEEE Industrial Electronics Society’s Dr. Eugene-Mittelmann Achievement Award for outstanding technical contributions to the field of industrial electronics, (ii) Anthony Hornfeck award for outstanding service to IEEE IE Society, (iii) IEEE Fellowship for contributions to ac and switched reluctance motor drives, (iv) Archer award for IP contributions from Regal Beloit Corp., (v) IEEE Industrial Electronics Distinguished Lecturer, (vi) Best book award from Ministry of Education and Sport, Poland, in 2003 for my coauthored book, Control in Power Electronics, (vii) six Best Paper Prize Awards from the IEEE Industry Applications Society, (viii) First Prize Paper Award from the IEEE Transactions on Industry Applications, (ix) Best Paper Award from the IEEE Industrial Electronics Magazine in 2007, and (ix) Life membership of AdCom, IEEE IE Society.

Teaching Experience: (i) College of Engineering, Guindy, Anna University, 1972-79, (ii) Concordia University, Canada 1979-81 and (iii) Virginia Tech 1985 – present.

Short courses: Delivered and organized a large number of short courses to industry in Electric motor drives, Power electronics, PM synchronous motor drives, Induction motor drives and Switched reluctance motor drives (all in USA, France, Italy, France, Greece, Korea, Portugal, and Denmark).

Specific Contributions in SRM Drives: He made original contributions in SRM drives in their modeling, simulation, analysis and design. He led the development of the computer aided analysis tools for SRM drives in 1986. His original work covers analysis and novel configurations and designs of axial field, radial field and linear SR machines for various applications from electric bikes, fans, pumps, air conditioner compressor motor drives, and air craft actuators, various power converters including low cost patented ones (one-switch power converters for four-quadrant operation) and their control for various applications, control strategies and control implementations for SRM drives, rotor position sensor-less control of SRM drive, linear motor drives for traction and maglev with SRM systems.

Consulting: Served as a consultant to more than 18 companies in USA.

Industrial Experience: Served in two US companies full time: (i) Principal engineer in Gould Inc, Rolling Meadows, Ill (‘82-‘85), and (ii) Business Leader and CTO of Ramu Inc., Regal Beloit America, Blacksburg, VA (’11-‘14).

Founder of two motor drives companies: (i) Panaphase Technologies which was acquired by Delta-Gee in 2007, and (ii) Ramu Inc., which was acquired by Regal Beloit Corporation in 2011 and also served as founding CEO and CTO for them. He has the distinct honor to be the only faculty in his area of research in the world to have started, operated and sold two successful companies in motor drives.

Current interests: (i) Writing books on motor drives, power electronics and control and he is writing an advanced control book on PMSM motor drives at present, (ii) Starting companies in the same areas and making them successful, and (iii) Inventions in PM and SR motors and power converters for them and their controls.