| 摘要 |
PURPOSE:To generate torque of an electric AC motor almost to a fixed value controlling the total sum of an output DC current to a fixed value by decreasing a commutation overlapping angle of a separately excited inverter increasing an upper limit of an operation possible frequency. CONSTITUTION:When a commutation signal G1 is input, a switch 18 is closed with a firing signal Ph8a obtaining a value corresponding to e-B by a subtracter 22 and with a firing signal Ph8b obtaining a value e+B by an adder 21. As a result, both converters (8a), (8b) obtain in their output DC currents Ipa, Ipb the characteristic as shown in a period G1 of (a), (b). When a commutation signal G2 is input, a switch 19 is closed with the firing signal Ph8a obtaining the value e+B by an adder 20 and with the firing signal Ph8b obtaining the value e-B by a subtracter 23. Thus, the DC current is decreased, only at the time of its commutation, to both inverters decreasing a commutation overlapping angle. A sum of both the currents Ipa+Ipb to each inverter is in a fixed value not changed. In this way, an electric AC motor generates torque almost not fluctuating. |
