| 摘要 |
PURPOSE:To prevent the breakdown of a semiconductor switch group by judging a DC voltage value between upper and lower arms exceeds a fixed value of a DC current value and turning a breaker OFF. CONSTITUTION:A brushless-motor protective device is constituted of a semiconductor switching group 2 controlling conduction currents to a winding 3 for a brushless motor, a phase detecting means 5 detecting the position of the magnetic pole of a rotor 4, a drive means 6 for said switching group 2, a DC voltage detecting means 8 and a DC current detecting means 9 detecting a DC voltage value between upper and lower arms, a DC current decision means 10, a timer means 11, and a make and break means 12 between said switching group 2 and the motor winding 3. The strength of external air force is detected by DC voltage, and the breaker 12 is kept OFF for a fixed time when the strength of external air force reaches a fixed value or more. When external air force increases on operation and the state of overload is detected and a DC current value exceeds a prescribed value, all elements in the semiconductor switching group 2 are kept OFF for a fixed time.
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