| 摘要 |
PURPOSE:To extend a speed controlling range of a polyphase AC motor by detecting the effective and reactive currents of the output phase without delay by the calculation of sinusoidal and cosine values corresponding to the real current value and the instantaneous voltage phase of the output phase of a stationary power converter. CONSTITUTION:An input current to an induction motor 3 is detected by current transformers 5a-5c, and V and W phase current detection signals 12v, 12w are applied through subtractor 7a and multiplier 7b of an effective current detector 7 to a D/A converter 7c. A U phase current detection signal 12u is applied to a D/A converter 7d as it is. Further, a pulse train 13 synchronized with the U phase voltage phase is applied from a controller 4 to the detector 7, is counted by a counter 7e and is inputted to memories 7f, 7g, which store in advance cosine and sinusoidal values and output addressed data. Converters 7c, 7d output the product of the input signals and feed back effective current signal 14' of the output of an adder 7h. The reactive current can be obtained by partly modifying the structure of the detector 7. |
