ABSTRACT
The protection of motors varies considerably and is generally less standardized than the protection of the other apparatus or parts of the power system. This results from the wide variety of sizes, types, and applications of motors. The protection is principally based on the importance of the motor, which usually is closely related to the size. This chapter deals with motors and the protection applied directly to them. Backup often associated with the connecting circuits is discussed in Chapter 9. The present discussion is for motors that are switched by a circuit breaker, contactors, or starters and for which the protection is separate from these devices and from the motor. Essentially, this covers motors at the 480-600 V level and higher. Not covered specically or directly are motors for which the protection is built into the motor or starter or for which fuses are the only protection.
