www.irf.com

1

International Rectifier

• 233 Kansas Street, El Segundo, CA 90245 USA

IGBT Protection in AC or BLDC Motor Drives

by Toshio Takahashi

The new IR2137 IGBT Gate Driver IC integrates Ground Fault and Over-Current Protection

with Soft Shutdown, thus providing a compact and comprehensive IGBT protection scheme.

1. INTRODUCTION

In the last decade, industrial AC drives have become more advanced in performance and more

compact in size. This is largely due to the rapid development of power silicon technology, including

the enhancement of IGBTs and of High Voltage Integrated Circuits. Additionally, this technological

growth has been particularly accelerated for low horsepower (< 5 Hp) AC Drives. Yet the ground fault

protection, a feature sought increasingly in motor drives of all power levels, is available widely only in

the high-end models due to the sensors and other circuitry involved. The market, however, continues

to demand a fully protected, yet inexpensive, system. To meet this demand, International Rectifier

has introduced the IR2137: a new generation 3-phase IGBT gate driver, featuring full IGBT protec-

tion and advanced soft shutdown features.

To understand traditional methods of IGBT protection, read Section 2. To understand the working of

the IR2137 skip to Section 3.

2. TRADITIONAL METHODS OF IGBT PROTECTION

2-1 Background Theory for Protecting Against Failure

One of the most common, and fatal, AC drive faults for IGBTs is the Over-Current condition. Table 1

outlines the causes for the three most common Over-Current modes.

Over-Current Mode

Potential Causes

Line-to-Line Short

Mis-wiring, Motor leads shorting, Motor phase-to-phase

insulation breaking down

Ground Fault

Motor phase-to-phase insulation breaking down

Shoot Through

False IGBT turn-on

Table 1: Potential Causes of Over-Current