| 摘要 |
PURPOSE:To eliminate the primary current detecting AC unit for a motor and to reduce the number of resistor stages by detecting the voltage across a shunt resistor which is connected in series with a metallic resistor at the secondary side of a wound-rotor type induction motor and sequentially reducing the secondary resistance due to a slip frequency. CONSTITUTION:A shunt resistor 15 is connected in series with the secondary side metallic resistor 4 of a wound-rotor type induction motor. The voltage across the shunt resistor 15 is inputted to an electromagnet 16 of a cam switch operating circuit 8 in a cam type start controller 5. Accordingly, a movable contactor 17 and an electromagnet 17 repeat attraction and repulsion in response to the frequency of the secondary current of an induction motor 3, timers T1-Tn sequentially operate upon rise of the speed of the motor 3, and cam switches 6 for shortcircuiting the resistor 4 are sequentially thrown. |
