Method and apparatus for controlling single or multiphase A.C. p

Details Method and apparatus for controlling single or multiphase A.C. p Method and apparatus for controlling single or multiphase A.C. p

1990-02-05

1993-08-24

Shoop, Jr., William M.

Electricity: motive power systems

Induction motor systems

Primary circuit control

318807, H02P 0540

Patent

active

052392520

ABSTRACT:
In the control of a.c. power controllers by the phase-angle control of semiconductor valves that are used to automatically control the power factor, it is necessary to determine the phase-angle between the current I and the voltage U by measuring the time difference between the current zero crossing and the voltage zero crossing. However, disturbances superimposed on the line voltage produce considerable statistical fluctuations, particularly in the measurement of the times for the voltage zero crossings. These fluctuations are propagated to the phase-angle and may lead to an unstable control response. Therefore, to determine the time difference, a reference time, which is calculated from the measured actual times of the preceding voltage zero crossings, is used for the voltage zero crossing.

REFERENCES:
patent: 4355274 (1982-10-01), Barbeau
patent: 4361792 (1982-11-01), Davis, Jr. et al.
patent: 4469998 (1984-09-01), Nola
patent: 4767975 (1988-08-01), Vasworth
patent: 4950970 (1990-08-01), Davis, Jr. et al.

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