Woodworker's Journal 1993-17-2, страница 19

Troubleshooting Electric Motors

What to do when the motor quits

by Jim Barrett

Because a woodshop environment is tough on electric motors, sooner or later you'll be faced with motor repairs or outright replacement. When motor troubles do arise, the usual course of action is to take the motor to a qualified repair shop or service center: there, the problem can be quickly diagnosed and fixed. However, you'll be a step ahead of the game if you can learn to identify some of the more common motor problems and determine whether or not the motor is actually damaged, or if the trouble stems from some external cause that you can remedy yourself,

I must tell you up front, though, that it's not a good idea to take any clcctric motor apart unless you have the experience and tools to do it. After interviewing the technical representatives at several major motor companies (Marathon, Baldor, and Emerson), all agreed that troubleshooting and repair of internal motor parts should be handled only by a qualified repair shop. While the motor manufacturers are looking at it largely from a product liability standpoint, there are several good reasons for this viewpoint.

The most important reason you shouldn't attempt to repair March/April 1993

electric motors yourself is that most involve lethal amounts of electrical current: if you happen to reassemble a motor incorrectly, there's a possibility of electrifying the motor frame, which in turn could give you a potentially deadly electrical shock when you use the tool {not to mention frying the motor itself). Also, you usually need specialized tools and diagnostic equipment to troubleshoot and replace most internal motor parts—bearings, internal switches, motor windings, rotors, and so on. Finally, if the motor is still under warranty, any attempted repairs made by the user will void the warranty.

In this article, I'll discuss what can go wrong with motors, which troubleshooting procedures and repairs you can do yourself, and which should be left to a pro.

Motor Basics

Two basic types of problems can occur with an electric motor: electrical and mechanical.

Electrical problems are those that relate to the motor circuitry—typically switches, wiring, and related electrical components. Examples are a faulty sw itch or capacitor, worn