| 摘要 |
PURPOSE:To eliminate the speed of a motor due to its overheat by discriminating the abnormal temperature of the motor based on a temperature detection signal and switching the speed command signal from the first speed signal generator to the second speed signal generator. CONSTITUTION:The rotating speed of a motor 3 for a sewing machine is controlled by passing a signal of the first speed signal generator 17 and a signal of the second speed signal generator 18 for instructing a rotating speed lower than the signal of the first generator through a switching circuit 19. A temperature detector 15 is provided at a housing of a motor 2, the signal of the detector is inputted to a discriminator 16, and the circuit 19 is controlled by the output signal of the discriminator. Accordingly, when the motor 2 continues the maximum speed operation to be overheated, a command signal is automatically switched from the generator 17 to the generator 18, thereby lowering the rotating speed, and improving the working efficiency without stopping the motor 3 at every overheated time. |
