Technical Data Bulletin

© 2020 Schneider Electric
All Rights Reserved
12/2/2020
7-47
www.se.com/us
Instantaneous Trip Circuit Breakers Motor Circuit Protectors
Class 600 / Refer to Catalog 0612CT0101
Instantaneous Trip Circuit Breakers for Motor Protection
Applications
Adjustable instantaneous-trip circuit breakers are intended for use in combination with
motor starters with overload relays for the protection of motor circuits from short circuits.
Other specific applications include rectifiers and resistance welders. These circuit
breakers contain a magnetic trip element in each pole with the trip point adjustable from
the front. Interrupting ratings are determined by testing the instantaneous-trip circuit
breakers in combination with a contactor and overload relay.
Select instantaneous-trip circuit breakers as follows:
This selection table is suitable for motors, other than NEMA Design E, with locked-rotor
indicating code letters per NEC
®
Table 430.7 (b) as follows:
Table 7.94: Locked-Rotor Indicating Codes
Horsepower
Motor Code Letter
1/2 or less
3/4 to 1-1/2
2 to 3
5 to 25
30 to 125
150 or more
A–L
A–K
A–J
A–H
A–G
A–F
•
For other motors order a special thermal-magnetic circuit breaker with magnetic trip
settings for the specific motor— specify motor horsepower, voltage, frequency, full-
load current and code letter or locked rotor current.
•
Determine motor hp rating from the motor nameplate.
•
Refer to the tables and select an instantaneous-trip circuit breaker with an ampere
rating recommended for the hp and voltage involved.
•
Select an adjustable trip setting of at least 800%, not to exceed 1300%, of the motor
full-load amperes (FLA) for other than Design E motors. For Design E motors, select
an adjustable trip setting of at least 1100% not to exceed 1700% of FLA.
•
The NEC 1300% maximum setting may be inadequate for instantaneous-trip circuit
breakers to withstand current surges typical of the magnetization current of
autotransformer type reduced voltage starters, or open transition wye-delta starters
during transfer from “start” to “run,” constant hp multi-speed motors, and motors
labeled “high efficiency.” Select thermal-magnetic circuit breakers for those
applications.
•
Part-winding motors, per NEC 430.4, should have two circuit breakers selected from
the above at not more than one half the allowable trip setting for the horsepower
rating. The two circuit breakers should operate simultaneously as a disconnecting
means per NEC 430.103.
•
Based on NEC 430.52 and NEC Table 430.250.
7
MINIATURE AND MOLDED CASE
CIRCUIT BREAKERS