| 摘要 |
PURPOSE:To protect a motor from deteriorated service life by eliminating circulation current, the circuitry uses connecting a negative resistance element which undergoes breakover when a given voltage is applied across speed terminals to be connected. CONSTITUTION:Setting the speed changeover switch 14 to the high-speed contact 141 allows current to flow through the high-speed terminal 12 and the motor 7. This also applies power voltage to the motor 8 causing the negative resistance element 18 to undergo breakover, and, as a result, the current passes through the high- speed terminal 13 to perform high-speed running. If, due to some reason, both motors 7, 8 differ in speed to cause a potential difference between the low-speed terminals 15, 16, the negative resistance element 19 remains in nonconducting condition, thus preventing the flow of circulation current. |
