| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to synchronously operate a brushless DC motor without stopping its rotation by a method wherein the motor during an asynchronous rotation is set to a nonelectrified state, a voltage at a voltage frequency which is higher than a synchronizing signal corresponding to the rotor speed of the motor is output for a short time and the motor is returned to the synchronous operation at the synchronizing frequency. SOLUTION: A brushless DC motor 14 during an asynchronous operation is set to a nonelectrified state by turning off a switching-element group 2 as a whole, the initial biaxial output voltage and the initial output frequency of the motor 14 are computed on the basis of the biaxial-current increase rate of the motor 14, on the basis of respective characteristic values, on the basis of a rotor speed and on the basis of a rotor phase so as to be output to the motor 14 only during its start time. After the start time has elapsed, an output- voltage effective value is changed, also an output frequency is changed to a synchronizing frequency, and the motor 14 is set to a synchronous operation as it is. Thereby, the brushless DC motor which does not have a rotor-position detecting means coupled directly to the motor 14 can be started by a motor current in a short time. |
