Automatic voltage selector control circuit for test sets with tap selectable line input transformers

An input adaptable electrical device comprising:

• an input for receiving an input voltage from an unidentified power source;
• a main transformer having a primary winding and a secondary winding, the primary winding of the main transformer connected to receive the input voltage from the input, the primary winding of the main transformer having first, second and third transformer taps that allow the main transformer to be configured in a first configuration or a second configuration;
• a circuit breaker connected between the input and the primary winding of the main transformer, when ‘open’ the circuit breaker prevents the input voltage from being provided to the primary winding of the main transformer and when ‘closed’ the circuit breaker allows the input voltage to be provided to the primary winding of the main transformer;
• and
• an automatic input voltage detection circuit connected to monitor the input voltage provided by the unidentified power source, wherein the automatic input voltage detection circuit identifies the power source based on the monitored input voltage, and selects the first configuration or the second configuration of the main transformer based on the identification of the power source, the automatic input voltage detection circuit including:
• a step-down transformer having a primary winding and a secondary winding, the primary winding connected to the input to receive the input voltage;
• a first relay connected to the second tap of the main transformer, the first relay being energized to selectively configure the main transformer in the first configuration;
• a second relay connected to the third tap of the main transformer, the second relay being energized to selectively configure the main transformer in the second configuration;
• and
• an auto-volt comparator circuit connected to monitor a stepped-down voltage provided by the secondary winding of the step-down transformer that is representative of the input power, wherein the auto-volt comparator circuit identifies the power source based on the stepped-down voltage and in response selectively energizes either the first relay or the second relay to configure the main transformer.