Method and apparatus for sensing voltage in an automatic transfer switch system
AssigneeKohler Co.
InventorsZane C. Eaton, Eric Albsmeier
Life of this patent
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Abstract
An Automatic Transfer Switch System includes a control circuit in which high frequency transformers, designed to operate linearly in a frequency range above the operating frequency range of utility-level power, are employed for voltage sensing. An output signal from a high frequency line matching transformer is received by a microprocessor which evaluates the signal for both a voltage level and frequency and uses these values as indices to an empirically-derived look-up table which provides an actual voltage level to the microprocessor. The actual voltage value can then be evaluated by the microprocessor to determine if and when the power delivered to a load should be supplied by a first or a second power supply.
Claims23
An automatic transfer switch circuit for switching a utility-level line power supplied to a load between a first AC power source and a second AC power source, the automatic transfer switch circuit comprising:
- a first high frequency transformer electrically connected to a utility-level power line from the first AC power source;
- a second high frequency transformer electrically connected to a utility-level power line from the second AC power source;
- and
- a processing unit electrically connected to each of the first and second high frequency transformers to receive a sensed voltage signal indicative of a level of the utility-level line voltage supplied by the respective power sources, wherein the processing unit is programmed to determine an actual level of voltage supplied by at least one of the first and second AC power sources based on the sensed voltage signal and to switch the power applied to the load from one of the first and second power sources to the other of the first and second power sources when the actual voltage applied to the load falls below a predetermined value.
An automatic transfer switch comprising:
- a first high frequency transformer electrically connected to a first AC power source and a second high frequency transformer electrically connected to a second AC power source producing a utility-level power supply, wherein one of the first and second AC power sources is electrically connected to a load to supply the utility power to the load;
- a processing unit electrically connected to each of the first and second high frequency transformers to receive a sensed voltage signal indicative of a level of output voltage of the respective power sources;
- a memory component storing a look-up table, the look-up table correlating a voltage level and a frequency of the sensed voltage signal to an actual voltage output from the one of the first and second AC power sources that is electrically connected to the load;
- wherein the processing unit is programmed to determine the frequency and the voltage level of the sensed signal and to correlate the sensed signal to the actual voltage level in the look-up table based on the voltage level of the sensed voltage signal and the frequency of the sensed voltage signal.
A voltage sensing circuit for sensing a level of an applied utility-level line voltage provided by an AC power supply providing utility power, the voltage sensing circuit comprising:
- a processing unit;
- a high frequency line matching transformer electrically coupled to an AC power source and to the processing unit to provide a sensed voltage level to the processing unit;
- and
- a temperature sensor coupled to the processing unit to provide a temperature sense signal;
- wherein the processing unit is programmed to sample a level of the sensed voltage from the high frequency line transformer, calculate a frequency of the sensed voltage and to determine an actual voltage provided by the AC power source based on the sensed voltage, the frequency, and the temperature.
Dependencies are inferred from the claim text.