×

Method and apparatus for standstill recognition when restarting a power converter-fed AC motor without a tachometer generator

  • US 5,635,811 A
  • Filed: 06/07/1995
  • Issued: 06/03/1997
  • Est. Priority Date: 06/30/1994
  • Status: Expired due to Term
First Claim
Patent Images

1. A method for recognizing a standstill condition of a three-phase AC motor driven by an inverter, the method comprising the steps of:

  • a) driving the inverter for a first time duration to induce a DC current through a phase of the three-phase AC motor;

    b) during the first time duration, measuring a time characteristic of a motor current and recording an energy component of the motor current and a reactive component of the motor current;

    c) after the first time duration has lapsed, turning off the inverter for a second time duration;

    d) after the second time duration has lapsed, driving the inverter for a third time duration so as to short-circuit the three-phase AC motor;

    e) during the third time duration, measuring the time characteristic of the motor current and recording the energy component of the motor current and the reactive current component of the motor current;

    f) after the third time duration has lapsed, calculating an average value from the energy component of the motor current recorded during the third time duration;

    g) comparing the average value to a preselected limiting value;

    h) comparing an upper range value of the energy component of the motor current, recorded during the third time duration, to a predefined limiting value; and

    i) determining that the three-phase AC motor is at a standstill if the average value during the third time duration is greater than the predefined limiting value and the upper range value is positive.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×