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AssigneeGeneral Signal Power Systems, Inc.
InventorsKevin R. Mengelt, Mark L. Schultz
Estimating the term…
An uninterruptible power system having a main power path between input and output terminals monitors the phase of the voltages at the input and output terminals while power is applied to the input terminals from an AC power source. The phase difference between the voltages at the input and output terminals is determined and, upon occurrence of a fault in the power supplied to the input terminals, an inverter is turned on to provide power to the load at a frequency which matches the frequency of the input voltage before the fault and at a phase which is the phase of the voltage at the input terminals before the fault corrected in accordance with the phase difference determined before the fault. Prior to transfer of the supply of power back to the main AC power source when the fault ends, the phase and frequency of the voltage at the input terminals is again measured. The frequency of the voltage from the inverter is adjusted to match that of the voltage at the input terminals, while the phase is adjusted to the phase of the input voltage corrected by a selected phase difference. The selected phase difference may be the last phase difference determined before occurrence of the fault, or a phase difference which is corrected based on the current drawn by the load where the phase shift between the input and output terminals in the uninterruptible power system changes as a function of load current.
An improved uninterruptible power system of the type having input terminals connectable to an AC power source, output terminals connectable to a load, a main power path between the input and output terminals, a power transfer device in the main power path which affects the phase of the voltage at the output terminals as compared to the phase of the voltage at the input terminals, an auxiliary power source, an inverter connected to the auxiliary power source to provide power when needed to the output terminals, a controllable switch in the main power path to selectively isolate the input terminals from the output terminals, and a controller which determines when a fault has occurred in the power supplied from the AC power source and, in response, opens the switch to isolate the input and the output terminals and turns on and controls the inverter to supply AC power to the output terminals at a selected frequency and phase, the improvement comprising:
A method of transferring the supply of power in an uninterruptible power system having input terminals connected to an AC power source, output terminals connected to a load, and a main power path between the input and output terminals with a power transfer device in the main power path which affects the phase of the voltage at the output terminals as compared to the phase of the voltage at the input terminals, comprising the steps of:
Dependencies are inferred from the claim text.