EP0051903A1
Expired / Lapsed
EP
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Three phase power factor controller
Assignee: National Aeronautics and Space Administration
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Filing: 1981-01-22
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Granted: —
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Expires: 2001-01-22
Abstract
Abstract A power consumption reducing control circuit for a three phase induction motor (10), wherein power factors (P1, P2, P3) for the three phases (A, B, C) are separately determined and summed to provide a composite control signal, which is suitably conditioned (64, 66) and then employed to control the duty cycle of each phase of input power to the motor (10) through the appropriately timed gating of thyristors or Triacs (12, 14, 16).
Inventors
- 👤 Frank Joseph Nola
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 05:12
CPC Classifications
H; H02; H02P; H02P7/00; H02P7/06; H02J; H02J3/00; H02J3/18; H02J3/1892; H02P23/00; H02P23/26
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
144 words
A power factor control system for a three phase A.C. induction motor comprising: first, second, and third phase detection circuits for sampling the current and voltage in each of said three phases and providing discrete outputs each proportional to the in-phase state of one phase; summing and integration circuitry for combining the three outputs of said detection circuits and deriving therefrom an averaged signal; a power factor command signal; a difference circuit for subtracting said command signal from said averaged*signal and providing a control signal; and control circuitry including a discrete signal responsive switch connected in series with each phase input of said motor, each switch being responsive to said control signal for varying the "on" time of the switch during each cycle of input power to an associated motor phase as a direct function of load on said motor and/or input voltage fluctuations.
Claim 2
Dependent Claim
144 words
A power factor control system for a three phase A.C. induction motor comprising: first, second, and third phase detection circuits for sampling the current and voltage in each of said three phases and providing discrete outputs each proportional to the in-phase state of one phase; summing and integration circuitry for combining the three outputs of said detection circuits and deriving therefrom an averaged signal; a power factor command signal; a difference circuit for subtracting said command signal from said averaged*signal and providing a control signal; and control circuitry including a discrete signal responsive switch connected in series with each phase input of said motor, each switch being responsive to said control signal for varying the "on" time of the switch during each cycle of input power to an associated motor phase as a direct function of load on said motor and/or input voltage fluctuations.
Claim 3
Dependent Claim
77 words
A power factor control system as set forth in claim 1 wherein: each switch comprises an SCR, and there is an oppositely polarized rectifier connected across each SCR; each phase detection circuit samples one-half cycle of electrical current and voltage; and said summing and integration circuitry includes circuitry for effecting, with an increase in frequency, a lag function, then a diminished lag function, and finally an increased lag function, whereby the stability of motor operation is enhanced.
Claim 4
Dependent Claim
98 words
A power factor control system as set forth in claim 2 wherein: said control circuitry includes a half wave signal ramp generator and a comparator for each phase; each comparator includes circuitry responsive to said averaged signal and a signal from one of said ramp generators for providing a gating signal having a width which varies inversely as a function of the amplitude of said averaged signal; and a high frequency signal and gating circuit responsive to said gating signals from said comparators for individually applying said high frequency signal as a "turn on" signal to said SCR's.
Claim 5
Dependent Claim
70 words
A power factor control system as set forth in claim 1 wherein: each switch comprises a Triac; each phase detection circuit samples both half cycles of alternating current input to an associated phase; and said summing and integration circuitry includes circuitry for effecting, with an increase in frequency, a lag function, then a diminished lag function, and finally an increased lag function, whereby the stability of motor operation is enhanced.
Claim 6
Dependent Claim
95 words
A power factor control system as set forth in claim 4 wherein: said control circuitry includes a full wave signal ramp generator and a comparator for each phase; each comparator includes circuitry responsive to said averaged signal and a signal from one of said ramp generators for providing a gating signal having a width which varies as an inverse function of said averaged signal; and a high frequency signal and gating circuit responsive to said gating signals from said comparators for individually applying said high frequency signal as a "turn on" signal to said Triacs.
References Cited (Backward Citations)
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