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Mine Safety and Health Administration MSHA's Accident Prevention Program
Safety Idea

Auxiliary Power Source Interlocks

Safety Something YOU can live with!
Mine Type: All Mines
Category: Electrical, Maintenance and Mobile equipment


Auxiliary Power Source Interlocks A failsafe mechanically operated electrical interlock on motor-generator auxiliary power sources can prevent fatal electrical shocks.

When proper steps are not taken to isolate auxiliary power sources on draglines or other large equipment, voltages can feed back into other circuits. These voltages can result in injury or even death. The use of a failsafe mechanically operated electrical interlock on the motor-generators supplying power to the auxiliary power sources can prevent harmful or fatal electrical shocks. A failsafe mechanically actuated electrical interlock system prevents the main and auxiliary power sources from being connected to the same circuit at the same time. It requires a positive action that must be performed to start the motor-generator and opens all other circuits except the motor-generator auxiliary power source. An idea for such an interlock can be found using this link.

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Issued: 04/18/2007
Tag # AP2007 - 93451