Plenary Session Speakers
Prof. Joachim Holtz

Joachim Holtz graduated in 1967 and received the Ph.D. degree in 1969 from the Technical University Braunschweig, Germany.

In 1969 he became Associate Professor and, in 1971, Full Professor and Head of the Control Engineering Laboratory, Indian Institute of Technology in Madras, India.

He joined the Siemens Research Laboratories in Erlangen, Germany, in 1972.

From 1976 to 1998, he was Professor and Head of the Electrical Machines and Drives Laboratory, Wuppertal University, Germany.

He is presently Professor Emeritus and a Consultant.

Dr. Holtz has extensively published, among others 12 invited papers in journals. He has earned 15 Prize Paper Awards. He is the coauthor of seven books, and holds 33 patents.

Dr. Holtz is the recipient of the IEEE Industrial Electronics Society Dr. Eugene Mittelmann Achievement Award, the IEEE Industrial Applications Society Outstanding Achievement Award, the IEEE Power Electronics Society William E. Newell Field Award, the IEEE Third Millennium Medal, the Anthony J. Hornfeck Service Award, and the IEEE Lamme Gold Medal. He is a Life Fellow of the IEEE.

Dr. Holtz is Past Editor-in-Chief of the IEEE Transactions on Industrial Electronics, Distinguished Lecturer of the IEEE Industrial Applications Society and IEEE Industrial Electronics Society.

Reducing IGBT Switching Losses by Gate Charge Control

Abstract – IGBTs are voltage controlled switching devices. Their fast switching characteristics generate high voltage gradients which stress the motor winding insulation and generate undesired bearing currents in ac drive systems.

Electromagnetic interference may happen with other electronic equipment. Also the current gradients are high. They increase the diode turn-off losses by generating high reverse recovery currents.

Voltage gradients are conventionally reduced by feeding the controlling gate voltage through resistors. The IGBT gate capacitance then delays the gate voltage changes, and thus increases the transition intervals between switching states at the expense of higher switching losses.

The existing drawbacks are overcome, not using the gate voltage rather the gate charge as controlling variable for turn-on and turn-off. It is demonstrated that IGBTs represent nonlinear oscillatory dynamic systems which is owed to internal charge transfer between its capacitances. Acquiring feedback signals for conventional closed loop control and generating adequate gate voltage profiles within microseconds is impossible. It is the novel method of event triggered control that is used instead. It enforces preset values of voltage and current gradients while reacting to extremely fast changes of the collector-emitter voltage and the collector current. Experimental results using 6.6 kV / 1.2 kA IBGTs show that di/dt is reduced to 2 kA/µs and dv/dt from 4 kV/µs to 1 kV/µs while reducing the switching losses to 70%.

Applications in industry are shown.