| 摘要 |
PROBLEM TO BE SOLVED: To reduce noise and accurately estimate a value of a current applied to a motor while a motor is not turned over. SOLUTION: A frequency of a pulse current Im supplied to an inverter 15 from a diode bridge 11 is reduced in an estimation period and increased in a non-estimation period. A current I applied to a motor 30 is estimated by a current detection circuit 22 according to a voltage drop Vm produced in a resistor 14 by a pulse current Im in the estimation period, and the estimation result is supplied to a control circuit 20 as an output Va. The control circuit 22 estimates the preheating temperature of the motor 30 according to the output Va. |
