| 摘要 |
1,170,203. Control of A.C. motors; converting circuits. BROWN, BOVERI & CO. Ltd. 23 April, 1968 [25 April, 1967], No. 19037/68. Headings H2F and H2J. A three-phase motor 4 is supplied from a . frequency charger circuit comprising a diode bridge 5, 6, 7, for each phase, and a controlled rectifier 8, 9, 10, shunted across each of the bridges. A supply transformer has secondary windings 1, 2, 3 connected in a cyclic manner to the motor phase windings U, V, W, and the controlled rectifiers are triggered by two pulse trains which have the same frequency but are mutually phase-displaced. The frequency applied to the motor is the difference between the supply frequency and the firing pulse frequency, the direction of rotation being dependant upon which is the greater. If the two frequencies are equal, unidirectional voltage is applied to the motor. The magnitude of the motor voltage is a function of the phase displacement angle. The firing pulses are derived from a generator having a frequency six times the control frequency, the generator being connected to a divider having two outputs in opposite sense and whose frequency is three times the control frequency. The outputs from the divider are applied to an OR gate, one through a pulse shaper, and the other through a pulse shaper and a time delay device. The output from the OR gate is applied to a three-stage ring counter which distributes the triggering pulses to the controlled rectifiers 8, 9, 10, Fig. 3 (not shown); In a modification, the supply transformer has six secondary windings and diode circuits for each phase, Fig. 4 (not shown). |
