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

• US 20110199067A1
• Filed: 02/16/2010
• Published: 08/18/2011
• Est. Priority Date: 02/16/2010
• Status: Active Grant

• Current Assignee: Electrical Reliability Services Incorporated (Vertiv Holdings Co.)
• Original Assignee: Electrical Reliability Services Incorporated (Vertiv Holdings Co.)
• Inventors: Revak, Christopher J.
• Granted Patent: US 8,451,639 B2
• Time in Patent Office: Days
• US Class Current: 323/301
• CPC Class Codes: G01R 19/16547 voltage or current in AC supplies switching for protection H02H; circuits for emergency power supply H02J9/00
• CPC Class Codes: H02M 1/10 Arrangements incorporating converting means for enabling loads to be operated at will from different kinds of power supplies, e.g. from ac or dc
• CPC Class Codes: H02M 5/12 for conversion of voltage or current amplitude only

Abstract

An input adaptable electrical test set provides for the automatic detection of the power source connected to the test set, as well as automatic configuration of the test set to accommodate the identified power source. Prior to identification of the power source, a circuit breaker isolates a main transformer associated with the test set from receiving power from the power source. The main transformer includes a primary winding and a secondary winding, the primary winding having first, second and third tap positions that allows the transformer to be configured in one of two states depending on the power source connected to the test set. An automatic input voltage detection circuit monitors the input voltage provided by the unidentified power source and identifies the power source based on the monitored voltage. Based on the identification of the power source, the automatic input voltage detection circuit selects the configuration of the main transformer and the circuit breaker is closed to allow power from the power source to be supplied to the main transformer.

Claims

1. 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 a configuration of the main transformer based on the identification of the power source.

2. The device of claim 1, wherein the automatic input voltage detection circuit provides a visual indication of the identified power source.

3. The device of claim 1, wherein the automatic input voltage detection circuit includes:

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.

4. The device of claim 3, further including:

a first visual indicator activated by the auto-volt comparator circuit in responses to the first relay being energized; and

a second visual indicator activated by the auto-volt comparator circuit in response to the second relay being energized.

5. The device of claim 4, wherein the auto-volt comparator circuit includes:

a universal power supply connected to generate a first direct-current (DC) voltage based on the stepped-down voltage, the first DC voltage providing operational power to the auto-volt comparator circuit;

wherein the value of the DC voltage is independent of a magnitude of the stepped-down voltage;

a rectifier circuit connected to generate a second DC voltage based on the stepped-down voltage,

a comparator circuit that compares the second DC voltage to threshold values to identify the power source, the second DC voltage being proportional to a magnitude of the voltage provided by the power source.

6. The device of claim 5, further including:

a third relay connected to energize the first relay by communicating the first DC voltage to the first relay, wherein the third relay is selectively energized by the comparator circuit based on the identified power source; and

a fourth relay connected to energize the second relay by communicating the first DC voltage to the second relay, wherein the fourth relay is selectively energized by the comparator circuit based on the identified power source.

7. A method of automatically adapting an electric test set to accommodate a power source connected to provide power to the electric test set, the method comprising:

isolating a main transformer from the power source upon connection of the power source to the electric test set;

deriving operational power for an auto-volt comparator circuit based on voltage provided by the power source;

identifying the power source based on the voltage provided to the auto-volt comparator circuit;

selectively energizing one of a plurality of relays to configure a tapped position of the main transformer based on the power source identified by the auto-volt comparator circuit; and

applying the power source to the main transformer subsequent to configuration of the main transformer based on the identified power source.

8. The method of claim 7, further including:

providing a visual indication of the identified power source.

9. The method of claim 7, wherein deriving operational power for the auto-volt comparator circuit includes:

converting the voltage from the power source from an alternating current (AC) voltage to a direct-current (DC) voltage that has a constant voltage over a wide-range of AC voltages, wherein the DC voltage provides operational power to the auto-volt comparator circuit.

10. The method of claim 7, wherein identifying the power source based on the voltage provided to the auto-volt comparator circuit includes:

rectifying the voltage from the power source from an alternating current (AC) voltage to a direct-current (DC) voltage proportional to a magnitude of the voltage provided by the power source; and

comparing the DC voltage to threshold values to identify the power source.

11. The method of claim 7, further including:

delaying energizing one of the plurality of relays for a period of time following application of the voltage from the power source to the auto-volt comparator circuit.

12. An input adaptable test set comprising:

an input for receiving an unknown input voltage;

a main transformer having a primary winding and a secondary winding, the primary winding connected to the input through an input circuit breaker that when ‘

open’

prevents application of the unknown input voltage to the primary winding and when ‘

closed’

allows application of the unknown input voltage to the primary winding, the primary winding have a first tap, a second tap and third tap that allows the main transformer to be configured in a first state or a second state;

a first relay connected to the second tap of the transformer, wherein when energized the first relay connects the main transformer in the first state;

a second relay connected to the third tap of the transformer, wherein when energized the second relay connects the main transformer in the second state;

a step-down transformer having a primary winding and a secondary winding, the primary winding connected to the input and configured to step down the unknown input voltage at the secondary winding; and

an auto-volt comparator circuit connected to the secondary winding of the step-down transformer that identifies the power source based on a stepped-down voltage provided by the step-down transformer, wherein the comparator circuit selectively energizes either the first relay or the second relay to configure the main transformer based on the identification of the power source.

13. The input adaptable test set of claim 12, wherein the auto-volt comparator circuit includes:

a universal power supply connected to generate a first direct-current (DC) voltage based on the stepped-down voltage, the first DC voltage providing operational power to the auto-volt comparator circuit;

wherein the value of the DC voltage is constant over a range of inputs associated with the stepped-down voltage;

a rectifier circuit connected to generate a second DC voltage based on the stepped-down voltage,

a comparator circuit that compares the second DC voltage to threshold values to identify the power source, the second DC voltage being proportional to a magnitude of the voltage provided by the power source.

14. The input adaptable test set of claim 13, further including:

a timer circuit that delays energization of either the first relay or the second relay for a period of time following application of power to the auto-volt comparator circuit.

15. The input adaptable test of claim 14, wherein the comparator circuit is a window comparator that averages the second DC voltage over a period of time and compares the average to the threshold values to identify the power source.