METHOD OF CONTROL OF OPEN CIRCUIT CURRENT FOR WINDINGS OF LINEAR INDUCTION MOTOR Russian patent published in 1998 - IPC

FIELD: electrical engineering. SUBSTANCE: lift cabin door is moved by linear induction motor with controlled voltage and frequency. Motor is driven by open current circuit for setting up the required profile of voltage indicated by increment linear coder with removed transmission factor of proportional and integral regulator. Magnetizing current insufficient for overcoming the door mass is added with 90 deg. shift relative to linear force current, and frequency is predetermined by open circuit and preset method. Signals which control voltage of pulse-width modulation are used to supply unalterable voltages of current polarity through three- phase low-pass filter to motor windings within precise time intervals in order to synthesize required sinusoidal currents of windings. Voltage is added after every crossing of zero of winding sinusoidal currents so as to surmount its delays. Linear reduction of voltage prevents door from falling at the end of its opening and closing. EFFECT: more reliable control. 6 cl, 14 dwg