Self-test method for digital or microprocessor-controlled overload protection arrangement

摘要

The method involves detecting a current flowing in three phases over a pre-settable period of time, and using a fraction of a smallest current value in the three phases detected during the pre-settable period as a test value of an over-current, instead of a predetermined over-current value of a normal operation. A period of time between the setting of the test over-current value and the point in time, in which the current flowing in all three phases falls under a pre-settable fraction of the nominal current value is determined. One sixth of the current value in the three phases detected during the pre-settable period is preferably used as the test over-current value.