| 摘要 |
733,883. Converters; automatic speed control. MULLARD RADIO VALVE CO., Ltd. Dec. 4, 1952, No. 30787/52. Classes 38 (2) and 38 (4). [Also in Group XXXVII] A supply and control system for an electric motor 30 in which the motor may be either synchronous or asynchronous and in which the speed of the motor may be maintained constant and be made to follow a set programme by the requisite application of a control voltage at a point 42 comprises an inverter 1, 2, 3 supplied by a rectifier 40, the output of the inverter feeding the motor 30. The frequency of the. inverter is under the control of a variable frequency oscillator 10, of the transitron type, which is fed with the control voltage from the point 42. The pulses developed by the oscillator 10 are fed into a ring counting unit 20 from which they are distributed to the grids of thyratrons 1, 2, 3 in the inverter. The output frequency of the inverter is thus one third of the oscillator frequency and is variable by means of variation in the control voltage at 42 and a potentiometer in the oscillator itself. A refinement in this control is provided by a tachometer generator 35 driven by the motor 30 the output of the tachometer generator being compared with the control voltage in a comparator 43 and the resultant fed into the oscillator. The voltage output from the rectifier 40 which is fed into the inverter is controlled by a series of delay circuits 41 whereby the instant at which the thyratrons are ignited is controllable thus altering the output voltage of the rectifier. The circuits 41 may be under the control of a potentiometer contained therein or may be under the direct control of the control voltage 42. Thus the well known requirement of induction motors that the applied voltage be substantially proportional to the supply frequency can readily be met. The ring counting circuit may be of the type disclosed in Specification 708,170, [Group XL (c)]. |
