Induction motor load monitor and control apparatus

Abstract

Induction motor load conditions are monitored by sensing the slip speed of the motor which is linear over a large operating range including the 100% load condition. Electronic trigger pulses are derived from motor shaft rotation to operate a one-shot waveform generator having a selected signal pulse time duration set at the 100% motor load condition to produce a 3.5 millisecond difference from the time between two trigger pulses. Thus, as the slip speed varies the signal pulse duration varies and thus becomes a monitor of the load condition. Both analog and digital embodiments are described, and utilization devices may be an analog meter display or an alarm circuit triggered by means of an intervening threshold comparison circuit. The monitoring circuits are used to sense variations of speed and indicate on a meter a scale factor of load or horsepower, etc. as related to various drive means without interconnections other than shaft speed detectors.

Dependencies are inferred from the claim text.