ABSTRACT
The protection of motors varies considerably and is generally less standard-
ized 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 con-
necting 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 to 600 V level and higher. Not covered specifically
or directly are motors for which the protection is built into the motor or
starter, or for which fuses are the only protection.
