| 摘要 |
PROBLEM TO BE SOLVED: To achieve overheat protection only through signal processing using components indispensable for motor control as they are by calculating the heating temperature of motor winding based on the detected operating state of a motor and protecting the motor when the heating temperature exceeds a specified level. SOLUTION: A control circuit 12 calculates the heating temperature of motor winding based on the r.p.m., voltage and current of a motor 1 detected, respectively, at a rotation detecting section 13, a voltage detecting section 14 and a current detecting section 15. The control circuit 12 is preset with a protection temperature. When the motor 1 is driven, the winding temperature normally increases but the calculated winding temperature is settled at a level lower than the protection temperature. When friction increases, a load is applied to the motor 1 and the current flowing through the motor 1 increases. When winding temperature calculated from increased current exceeds the protection temperature, current supply from a motor drive circuit 11 to the motor 1 is interrupted to stop rotation thus protecting the motor 1 against overheat. |
