PURPOSE: To protect a circuit breaker against overheating by making a decision whether a maximum detection signal has exceeded a set level upon detection of overcurrent and delivering a trip signal when the set level is exceeded thereby preventing the system down.
CONSTITUTION: A time limit operating time switching means 40 receives an overcurrent state detection signal from means 30 and a maximum value detection signal from means 20, makes a decision whether the maximum value detection signal has exceeded a set level upon detection of overcurrent, and switches the time limit operating time. A trigger means 50 delivers a trigger signal based on an output from the means 40 and detection signals from the means 20, 30. A trigger unit 158 functions based on the trigger signal. A trigger mechanism opens the circuit upon function of the trigger unit 158. This constitution prevents the system down caused by early triggering and protects a circuit breaker against overheat due to temperature rise.
TERAOKA WATARU
HAYAKAWA HIDEKI
HITACHI TECHNO ENG
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