| 摘要 |
PURPOSE:To prevent a battery voltage drop from causing erroneous detection of commutation failures by a method wherein currents in a chopper circuit are detected and signals representing the currents are used to put a commutation failure detecting circuit into operation, when a chopper circuit is made use of for the purpose of controlling a motor. CONSTITUTION:A chopper circuit 8 is used for the driving of a propelling motor 6 aboard a forklift truck or the like. A circuit detecting currents in the propelling motor 6 by means of a detector 7 and detecting circuit 23 for the controlling of a transistor TR3, is added to a stage preceding a commutation failure detecting circuit 19. A normal commutation causes a low potential output from the detecting circuit 23 to turn off the transistor TR3, while a commutation failure turns it on for the effectuation of protection against the failure. Accordingly, erroneous operations under lowered battery voltages can be prevented, it being so set that the absence of trigger signals and motor currents indicate no commutation failure and that there be no need for a protective operation under such conditions. |
