Electricity: power supply or regulation systems – Output level responsive – Using a transformer or inductor as the final control device
Patent
1996-06-24
1998-03-10
Krishnan, Aditya
Electricity: power supply or regulation systems
Output level responsive
Using a transformer or inductor as the final control device
G05F 116
Patent
active
057265615
ABSTRACT:
The apparatus and methods of the invention provide conversion of a wide range of utility voltages found worldwide, to a fixed nominal voltage level. The invention therefore provides the ability to "plug in" to virtually any power source, and produce a desired nominal voltage for operation of electrical equipment either alone or in conjunction with a UPS device. The voltage selection apparatus provides standard nominal levels of electrical power to equipment while utilizing power sources of varying voltage and frequency. The device is dynamically adaptive to the input power source, and maintains its output within a nominal range even where the input source varies to a substantial degree. The voltage selection apparatus comprises an input for receiving input AC voltage from a power source, and a transformer to produce an output voltage which is coupled to the input. The transformer has at least one winding and a predetermined plurality of winding taps used to achieve a desired nominal output voltage from the transformer. A voltage detector is coupled between the input and the transformer to selectively measure the input voltage and enable output of a selected nominal output voltage. A control circuit is coupled to the voltage detector and monitors the input voltage to produce control signals in response thereto. A plurality of relay devices, each being coupled in series with one of the winding taps are used to select a desired or required tap configuration. The relay devices are controlled by the control circuit to select a predetermined winding tap based upon the input voltage to produce an output from the transformer within a desired nominal voltage range. The invention also provides methods of operation for regulating output voltage from a transformer having a plurality of voltage taps and being supplied with an AC input voltage. A nominal output voltage is maintained by initiating required tap changes by detecting a zero crossing of the input voltage and turning off current to a switch coupling the selected tap to the input voltage. A determination of a different transformer tap to be selected to supply the nominal output voltage is made, and current is selectively supplied to the switch coupling the input voltage to the different transformer tap. The step of supplying current to the switch of the different transformer tap is performed at a predetermined time relative to turning off current to the switch of the previously selected tap based upon the different tap to be selected. The methods of the invention include a no-break tap change with forced commutation of current and synchronized tap change with natural current communication. The methods allow transformer tap changes without interruption of power to the load and/or with minimal transient current surges on the power line. It is also an object of the invention to provide an apparatus and methods which minimize tap selection changes.
REFERENCES:
patent: 5602462 (1997-02-01), Stich et al.
Besmen Mark E.
Ghosh Ramit
Krishnan Aditya
Universal Power Systems, Inc.
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