Electronic circuit breaker using digital circuit having instantaneous trip function

PURPOSE: To prevent erroneous tripping by setting short, long and instantaneous time constants and generating a trip signal when a signal from a current transformer exceeds respective values. CONSTITUTION: The electronic circuit breaker comprises a normally closed three-pole single throw switch 10, an electromechanical actuator 47, current transformers 14-16, over sampling Δ-Σ modulators 31-33, decimation filter 34-36, short time constant/long time constant trip signal generation circuits 44-46, and an OR gate. Short, long and instantaneous time constants are set previously. A signal from the decimation filter 34 is multiplied and integrated before being compared with the short and long time constants and it is also compared with the instantaneous time constant. A short, long or instantaneous trip is generated when a short, long or instantaneous time constant is exceeded. According to the arrangement, an arbitrary conductor can be protected. COPYRIGHT: (C)1991,JPO