| 摘要 |
<p>PURPOSE:To dispense with a resistance for preliminary excitation, by preliminarily exciting a field winding to perform the chopper actuation of a main switching element in regenerative operation. CONSTITUTION:An input of a switch signal of a forward contactor MF into an input port 7f turns ON the forward contactor MF and a main contactor MC, while a main switching element 5 is controlled by a preset chopper actuation frequency. A regenerative braking during forward travelling turns ON a switching element 8 for preliminary excitation and supplies the preliminary exciting current to a field coil FC. When the current is supplied, the main switching element 5 is controlled by the predetermined preliminary excitation chopper actuation frequency. Thus a resistance for preliminary excitation can be dispersed with.</p> |
