| 摘要 |
<p>A device is provided for determining the phase shift between the voltage and current supplied to a motor and a comparator means for comparing the determined phase shift to a predetermined limit value. A device is responsive to the comparator for varying the power supplied to the motor when the limit value is exceeded. The comparator is adapted to compare the determined phase shift to a lower limit value and to a higher limit value, the device responsive to the comparator being arranged to vary the power supplied to the motor when the determined phase shift is greater than the higher limit value or less than the lower limit value. - The device responsive to the comparator comprises a switch for interrupting the power supplied to the motor when a limit is exceeded. The comparator comprises a counter operative to count pulses generated by an oscillator during the time period extending between the time the voltage has passed through a predetermined phase value and the time the current reaches the same phase value. (19pp Dwg.NO.1/1)</p> |
