| 摘要 |
PURPOSE:To prevent a DC motor from overheat by short-circuiting its field winding during AC motor operation. CONSTITUTION:An AC motor 2 and a DC motor 3 are coupled to a common drive shaft 4, and the AC motor 2 is operated in normal basis while the DC motor 3 is operated when the AC motor 3 cannot remain in operation. An auxiliary contact point 15 is provided in parallel with a field winding 12 of the DC motor 3, which is closed, except when the DC motor 3 is in operation, by a control instruction transmitted by a control unit 5. The system being thus constructed, the DC motor field winding under short-circuited condition during an AC motor operation, no voltages are introduced in the DC motor, with no flux residual in the DC motor field system. No current consequentially flows in a starting resistor 13 or field resistor 14, preventing the two resistors from overheating. |
