| 摘要 |
In a PWM-controlled motor, a motor rotation frequency f, lock determination frequency d, and power supply voltage E are acquired (S 1 to S 3 ). The d is compared to the f (S 4 ). When f is not less than that of d, Max.Duty is calculated by the following equation for setting: Max.Duty=D 0 *Kf (S 5 , S 6 ). D 0 is an allowable Duty value and can be calculated by [DP 0 =a-bE] (a: fixed Duty value, b: Duty characteristic coefficient). Kf is a frequency adjustment coefficient. Kf corrects the allowable Duty value D 0 in accordance with the motor rotation frequency f and can be calculated by the following equation: Kf=1+(f-d)/c (c: restriction start frequency, d: lock determination frequency). When f is less than d, Max.Duty=D 0 is set (S 7 , S 6 ). When the motor enters a locked state, the Duty value is suppressed to not more than the allowable Duty value D 0 to thereby suppress a lock current. This reduces a lock current at low temperature time to prevent demagnetization of a magnet as well as reduces a load of a switching device.
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