Use of inverse time, adjustable instantaneous pickup circuit breakers for short circuit and ground fault protection of energy efficient motors

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:392601

Heath, D W ^[1]; Bradfield, H L ^[2]

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1. General Electric Co., Plainville, CT (United States)
2. Bechtel Corp., Houston, TX (United States)

Many energy efficient low voltage motors exhibit first half cycle instantaneous inrush current values greater than the National Electrical Code`s 13 times motor full load amperes maximum permissible setting for instantaneous trip circuit breakers. The alternate use of an inverse time circuit breaker could lead to inadequate protection if the breaker does not have adjustable instantaneous settings. Recent innovations in digital solid state trip unit technology have made available an inverse time, adjustable instantaneous trip circuit breaker in 15A to 150A ratings. This allows the instantaneous pickup to be adjusted to a value slightly above motor inrush so that low level faults will be cleared instantaneously while avoiding nuisance tripping at startup. Applications, settings and comparisons are discussed.

• OSTI ID: 392601
• Report Number(s): CONF-950920--; ISBN 0-7803-2909-0
• Country of Publication: United States
• Language: English

Related Subjects

24 POWER TRANSMISSION AND DISTRIBUTION
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
CIRCUIT BREAKERS
DESIGN
ELECTRIC MOTORS
ELECTRICAL FAULTS
ENERGY EFFICIENCY
OPERATION
SAFETY ENGINEERING
START-UP