MOTOR CONTROL APPARATUS WITH TRUE RMS NON SINUSOIDAL NEGATIVE SEQUENCE STATOR CURRENT PROTECTION MODE

摘要

58ABSTRACT OF THE DISCLOSUREA microprocessor-controlled motor starter inwhich the negative sequence component is determined bymonitoring the three-phase lines of a motor under startingconditions. The stator winding currents are converted tothe respective negative and positive sequence componentsin the microprocessor so that an RMS indication of theactual instantaneous current flowing in the stator windingsmay be had. This is true whether the current is sinusoidalor non-sinusoidal. By using an appropriate model for thethermal equivalent circuit for the rotor a predeterminedsafe value of current may be determined above which themotor starting or running action is aborted.