Author(s): Ali H. A. Al-Obaidly

In this paper the design of a safety electrical break for any DC motor especially the motor used with the DC-DC converter circuit is presented. The effect of ON time upon maximum current of the DC-DC converter is illustrated. The current increases as the ton increases. The effect of injected voltage upon DC chopper performance is illustrated. The injection-protected voltage has a pronounced effect upon the chopper maximum current. It is reduce current through the chopper till it reaches the threshold current present through the power switch data sheet. The DC chopper under investigation has two modes of operation when the injection voltage equal to 12V. Inversely, at another level of the injected voltage the chopper has only one mode of operation .At this case the chopper operation works at the discontinuous mode only. As the current through the switch decreases to the previous value, the power switch will be turned OFF immediately. After that the next pulse must be generated for triggering the switch once again. The electrical break for the DC chopper motor is safe because the reverse current injected to the DC chopper circuit is decreased step by step and not rapidly. Hence, the breaking of the motor becomes very safe. The proposed work is verified on test cases and proven to be reliable.