| 摘要 |
<p>METHOD AND SYSTEM FOR STARTING A MOTOR-COMMUTATED SCR INVERTER Highly reliable and consistent starting of an SCR inverter-motor system is achieved by first initializing the rotor position, namely establishing the rotor in a known starting position. Thereafter, the inverter is operated synchronously in a second mode with predetermined pairs of the inverter SCRs being sequentially gated into conduction at an increasing frequency to current pulse enerqize the motor to effect step-by-step rotation of the rotor at a faster and faster rate, the motor current being reduced to zero at the termination of each energizing pulse to force commutate the conducting pair of SCRs. After the motor has reached a preset speed, operation in a third mode occurs and the inverter is synchronized with the motor, gating of the SCRs being controlled by the motor voltage in order that the rotor position will be synchronized to the revolving magnetic field created by the stator. During this third operating mode the motor speed continues to increase and the SCRs are forced commutated, as a result of which the rotor follows the stator magnetic field very closely and synchronization will be perfected. When the motor subsequently reaches a given speed sufficiently high to permit motor commutation exclusively, the starting system switches to a fourth and normal running mode wherein the gating of the inverter SCRs continues to be synchronized with the motor and controlled by the motor voltage, but the SCRs will now be commutated only by the motor voltage,</p> |
