Method and measuring instrument for determining the slip frequency of asynchronous motors

摘要

The invention relates to a method and a measuring instrument for determining the slip frequency of asynchronous motors, a measurement being made by an inductive measuring sensor in the leakage field of the asynchronous motor and the inductive measuring sensor registering a resultant total voltage from the magnetic leakage field, which voltage results from superposition of the field voltage of the stator and the rotor voltage, the resultant total voltage detected by the receiver coil being squared in a subsequent squaring component, in which case a steep-edged bandpass is connected downstream of the squaring component, which bandpass is provided with a first and second low pass with separate signal paths, the output signals of which are connected to a subtractor. The voltage signals for the field frequency and the slip frequency are in each case counted in counters which are controlled by a microcomputer.