| 摘要 |
PURPOSE:To suppress a pulsation of a motor torque at a time of changing over secondary resistances together with to device increasing a life of a secondary resistance change over switch by decreasing a current in case of switching a secondary resistance change over switch. CONSTITUTION:A speed instruction is given by a speed establisher 6 then a speed regulator 7 is operated and a secondary resistance change over instruction device 13 makes ''on'' ''off'' switching secondary resistance change over switches MC1-MC4 adequately so as to be a secondary resistance value corresponding with a number of revolution detected by a tacho-detecting-generator 5 so that a real number of revolution becomes to be stable at an established speed. In this case a switching instruction of a secondary resistance change over switch and an operation signal of each secondary switch auxilialy contact are entered into operation detector 12 and through an OR element 14 a signal is transmitted to a primary current decreasing transistor 10 catching an instant when shifting to either open or closed whenever any secondary switch is operated. When this transistor 10 becomes conductive, an instruction to decrease a current is given to a current regulator 8 from a decreased current establisher 11. In this manner a secondary current is decreased at a switch operating time of a secondary resistance change over switch. |
