| 摘要 |
<p>1,051,411. Inverting; control of A.C. motors. LICENTIA PATENT-VERWALTUNGSG.m.b.H. Jan. 29. 1964 [Jan. 30, 1963; March 27, 1963], No. 3782/64. Headings H2F and H2J. The Specification relates to inverters whose output voltage and frequency can both be controlled, and is an improvement upon inverters of the type having an arrangement associated with each controllable element whereby the element can be turned off at a desired instant independently of the turning on of the next element in sequence. Such arrangements are used for induction or synchronous motor control (Fig. 1, not shown). An inverting arrangement comprises an inverter whose frequency is controllable but whose valves always have the maximum conduction angle (e.g. 120 degrees in a three-phase inverter) supplied from a D.C. source through a chopping arrangement comprising elements, such as thyristors with associated turn-off circuits, in one or both D.C. lines which operate at a higher frequency than the inverter and by varying their on-off ratio determine the input voltage to the inverter and hence the final alternating output voltage. The basic arrangement is shown in Fig. 2 in which battery Ug drives motor M through a three-phase inverter comprising thyristors 101 to 106. Feedback diodes and capacitors to aid commutation are connected as shown. Two methods of controlling the chopper elements are described. In Fig. 3 (not shown), which is a single-phase version of Fig. 2, one chopper element comprises a main thyristor 120 having in parallel with it the series combination of a further thyristor 122 and capacitor 121. When the main thyristor is not conducting the capacitor is charged through a diode and resistor connected in parallel with the further thyristor. To turn off the main thyristor the further thyristor is fired, so discharging the capacitor across the main thyristor to reverse bias it. In the arrangement of Fig. 4 (not shown), and Fig. 5, a bridge of thyristors switches a commutating capacitor across the D.C. lines. Free-wheeling diodes may be provided (Fig. 6, not shown).</p> |
