| 摘要 |
PCT No. PCT/SE95/00201 Sec. 371 Date Oct. 30, 1995 Sec. 102(e) Date Oct. 30, 1995 PCT Filed Feb. 24, 1995 PCT Pub. No. WO95/24073 PCT Pub. Date Sep. 8, 1995A device for controlling a three-phase induction motor that is driven by an inverter connection. The inverter is furnished to be fed with full-wave rectified grid alternating voltage (U) and supply the motor's various phases (R, S, T) with the drive voltages phase-displaced in the normal way and which consist of mainly square, in relation to a virtual zero reference level, positive and negative half-periods which alternate at a fixed or adjustable drive frequency corresponding to the required speed. The full-wave rectified grid alternating voltage (U) supplied to the inverter is arranged to be supplied to respective motor phase (R, S, T) via an electronic switch connection (TR1H, TR1L; TR2H, TR2L; TR3H, TR3L) whose respective on and off periods are determined by the drive frequency which is generated by an oscillator device (15; 25). The last mentioned is arranged to be supplied with a voltage (Um) which directly or indirectly represents the rectified grid alternating voltage (U) for the purpose of modulating the drive frequency with a signal that represents the variations in amplitude of the rectified grid alternating voltage. The invention also comprises a method of controlling an induction motor of the type specified. |
