A Practical Guide to Understanding Bearing （了解轴承的实用指南）.pdf

A PRACTICAL GUIDE TO UNDERSTANDING BEARING DAMAGE RELATED TO PWM DRIVES Don Macdonald Will Gray IEEE Member IEEE Member Toshiba International Corporation Toshiba International Corporation Abstract – The performance and reliability of AC Adjustable Speed Drives (ASDs) is continually improving. One of the Stator key reasons for improvement has been the advent, development and use of Pulse Width Modulated (PWM) Bearing Bearing drives utilizing faster switching devices, primarily Insulated Rotor Gate Bipolar Transistors (IGBTs). As with many other Shaft developments, improvements in some areas may cause problems in others. An increased bearing failure rate in motors is one of the negative effects of these types of drives. To mitigate bearing current damage in motors, as well as in loads and other auxiliary equipment attached to the motor shaft, it is important to understand how these currents are generated. In addition to theoretical explanations, actual field Base cases and solutions will be reviewed. Fig. 1 Inductive circulating currents 1. INTRODUCTION few turns within the slot. Since p