Appendix G: Power Supplies

Primary Disconnect

Provide a lockable means of positively disconnecting the input on large power supplies This disconnect must be clearly marked and accessible.

If provided with a built-in lock that is part of an interlock chain, the key must not be removable unless the switch or breaker is in the “off” position.

Overload Protection

Overload protection must be provided on the input and should be provided on the output.

Floating Power Supplies

Some research equipment (e.g., electrophoresis devices, x-ray tubes, and ion-bombardment power supplies) employs ungrounded (floating) power supplies. This equipment may operate in voltages ranging from 50V to kilovolts, with output capacities in excess of 50mA, and must be considered a lethal electrical hazard. Users of such equipment must take special precautions to minimize electrical hazards. Follow all manufacturers’ instructions for equipment use, testing, and training. The following general guidelines also apply:


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