Method and device for detection of current and automatic prevention of missetting of the nominal current values in electric motors

摘要

The invention relates to a method and a device for the detection of current and automatic prevention of missetting of the nominal current limit values in the case of electronic motor circuit-breakers. The motor current detected is, in this case, on the one hand compared with a nominal current limit value which can be altered by the user and, on the other hand, also compared with the same value so that I(Mot)/I(Nom) x is considered as a working comparison condition. An electronic functional unit, on which the start-up time and start-up current value can be adjusted, additionally generates motor status signals as well as a suitable envelope curve for further comparisons. The results of the comparisons are finally combined with each other, analysed and output. This guarantees a rapid switch-off which is not susceptible to interference, for protection of the motor (especially in the event of disasters), and simultaneously prevents excessively high and excessively low settings of the nominal current limit values.