| 摘要 |
PURPOSE:To enable to preferably detect the frequency accurately in good response by reading out a counted value from a counter whenever a sampling pulse is multiplied by integer times, detecting the actual frequency, and comparing and operating it with a reference frequency. CONSTITUTION:When a pulse number at every 30 deg. of electric angle is used as a sampling pulse SPLS, the counted value FCNT of an oscillation pulses PULS from an oscillator 603 oscillated at the prescribed period at every 10Hz of AC voltage signal of a counter 602 is read out by a computer 402. In this case, the counted value FCNT read out by the computer 402 becomes a reference counted value corresponding to the reference frequency of an AC system, but when variation occurs, it becomes different from the reference value. In this case, the difference of both controls the frequency by correcting the DC current reference value of a voltage converter. |
