| 摘要 |
PURPOSE:To limit an overhead power line current by a simple method wherein a signal corresponding to the flow rate and the current detector output signal are combined and the output is compared with a pre-set value for the control of the chopper circuit flow rate. CONSTITUTION:A detected motor current IM and a phase-shift command signal PC corresponding to a chopper flow rate alpha are supplied to an adder 25, and a limit setting value lS and the adder 25 output are processed in a comparator- operator 26 for an output SO that limits the overhead power line current by restraining the chopper phase-shift so that the overhead power line current IS may not exceed a pre-set level. This eliminate a multiplier as well as a line current detector and a very simple structure can be used to limit the line current. |
