Patent ID: 6236947
Filing Date: 2001-05-22
Classification: G01R

Abstract:
A method of checking placement of voltage and current probes on corresponding phases of a polyphase induction motor, comprising the steps of:(a) simultaneously sensing an instantaneous current signal supplied to the motor as a function of time for all three phases of the motor;(b) simultaneously sensing an instantaneous voltage signal supplied to the motor as a function of time for all three phases of the motor.(c) demodulating the sensed current and voltage signals to provide an RMS value and per phase values for the three current and the three voltage signals;(d) comparing each of the voltage and current probe signals to a first predetermined value of voltage and current respectively;(e) comparing a difference between the demodulated phase values of the three voltage signals and a particular voltage threshold (typically 30 degrees) in order to verify that any two or all of the voltage probes are not placed on the same phase;(f) requiring that the differences between the demodulated phase values of the three current signals are all greater than a particular current threshold in order to verify that any two or all of the current probes are not placed on the same phase; and(g) requiring that a cosine of the resulting power factor angles, respectively, of the three phases are positive and that a difference between a maximum and a minimum of the power factor angles of the three phases is less than a particular power factor threshold (typically 30 degrees) in order to verify that none of the current probes or voltage probes are switched or reversed.