| 摘要 |
PROBLEM TO BE SOLVED: To achieve stable and reliable changeover from synchronous operation to position detecting operation by changing the operation of a brushless DC motor to a position detecting operation provided that a present current phase or voltage phase has reached a given phase with which a stable changeover is made possible. SOLUTION: After a brushless DC motor 3 is started forcedly with a synchronous operation, a current effective value of the DC part of a three-phase inverter 2 is calculated and a present electric potential phase or current phase is obtained by applying the current effective value of the DC part of the three-phase inverter 2 calculated for a specific relation. Then, it is judged whether or not the obtained phase is within a preset range of an operation changeover phase. When the obtained phase is judged to be within the range, the operation is changed over to a position detecting one. This enables the operation of the brushless DC motor 3 to be stably and reliably changed over to the position detecting operation. |
