Electricity: motive power systems – Induction motor systems – Power-factor control
Patent
1983-04-25
1984-06-12
Dobeck, B.
Electricity: motive power systems
Induction motor systems
Power-factor control
318798, 318805, 318438, H02P 736
Patent
active
044544626
ABSTRACT:
The power factor for an AC induction motor (34) is controlled by selectively controlling the firing angle delay of a gate signal to a gate controlled power switch (36) during the cycle of the power source (32). Source voltage zero crossing (66) is sensed and a plurality of consecutively sequenced discreet windows (94, 96, 98, 100) are initiated. If the current zero crossing (68) occurs in the first window (94), then a sudden load on the motor (34) is indicated, and any delay in the firing angle of the power switch (36) is substantially eliminated. This enables conduction of the power switch (36) during substantially the entire cycle of the source voltage (60), thus providing instantaneous full power to the motor (34). If the current zero crossing (68) occurs in the second window (96), then the power factor is too great, and more power is needed at the motor (34). The gate firing angle is reduced, whereby the power switch (36) will conduct for a longer cycle portion and hence deliver more power to the motor (34). If the current zero crossing (68) occurs in the third window (98), then an optimum power factor is indicated and the gate firing angle is not affected. If current zero crossing (68) does not occur in any of the first (94), second (96) or third (98) windows, then it will occur somewhere in the fourth window (100) and too much power is getting to the motor (34). Upon termination of the third window (98) without zero crossing (68) of the current, the gate firing angle delay is increased so that the power switch (36) will be ON for a shorter portion of the cycle, and hence less power is delivered to the motor (34).
REFERENCES:
patent: 4052648 (1977-10-01), Nola
patent: 4070605 (1978-01-01), Hoeppner
patent: 4266177 (1981-05-01), Nola
patent: 4286303 (1981-08-01), Genheimer et al.
patent: 4290001 (1981-09-01), Espelage
patent: 4297628 (1981-10-01), Hedges
patent: 4322672 (1982-03-01), Walker
Intel Publication by Alex Toth, May, 1980, "Energy Savings in an Induction Motor Using the 8022.mu.".
McGraw-Hill-Dictionary of Scientific and Technical Terms, 1976, p. 1534.
Dobeck B.
Griggs Dennis T.
Moore Richard M.
Neha International
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