US3624837A
Expired / Lapsed
US
⏱️ 0.0 years remaining
MOTOR SPEED AND TORQUE CONTROL CIRCUIT WITH e.m.f. FEEDBACK
Assignee: US Philips Corp
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Filing: 1969-03-11
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Granted: 1971-11-30
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Expires: 1989-03-11
Abstract
Abstract A motor speed control circuit that includes an SCR in series with the motor across a source of AC supply voltage. A control circuit controls the SCR firing angle so that the effective current applied to the motor is substantially independent of the motor back e.m.f. The SCR control circuit includes a timing circuit that produces a time variable ignition pulse for controlling the SCR firing angle. The reference point for the timing circuit is that instant when the motor back e.m.f. equals the voltage of the trailing edge of the forward half cycle of the AC supply voltage. This choice of the reference point causes the SCR control circuit to advance the ignition of the SCR when the back e.m.f. increases, whereas prior art circuits delay the SCR ignition for increased back e.m.f. However, the overall conduction angle of the SCR remains approximately constant by virtue of a reset switch that resets the timing circuit at the aforesaid reference point. Thus, the effective motor current stays approximately constant within given limits.
Inventors
- 👤 Scato Albarda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:38
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/10; G05F1/12; G05F1/40; G05F1/44; G05F1/445; G05F1/45; G05F1/455; H; H02; H02J; H02J7/00; H02J7/02; H02J7/90; H02J7/933; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/292; H02P7/293; H02P7/295; H02J2207/00; H02J2207/20; Y; Y10; Y10S; Y10S388/00; Y10S388/907; Y10S388/917; Y10S388/919
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
259 words
An arrangemenT for controlling the direct current supplied from an alternating current source to a load across which it produces a reverse voltage comprising, at least one controlled rectifier connected in series with the load across said AC source, a control circuit by means of which the controlled rectifier is ignited during each forward half-cycle of the supply voltage with a controlled delay with respect to a reference instant at which the absolute value of a voltage proportional to said reverse voltage is equal to the instantaneous amplitude of the trailing edge of half a cycle of the supply voltage or of a voltage proportional thereto, so that, within certain limits, the effective current applied to the load is substantially independent of the reverse voltage produced across said load, and wherein said control circuit comprises a time-measuring circuit having a reset switch, the time-measuring circuit producing a pulse for igniting said controlled rectifier with a controlled time delay after the reference instant that is determined by the time-measuring circuit, a comparison circuit, means for applying to said comparison circuit the difference between the supply voltage and the reverse voltage, said comparison circuit including a voltage difference limiter followed by a differentiating circuit which produces pulses whenever the amplitude of the supply voltage is equal to the amplitude of the reverse voltage, and wherein the reset switch is controlled by the pulses derived from the differentiating circuit and is sensitive solely to control signals of a given polarity corresponding to that of the reset pulses corresponding to the reference instant.
Claim 2
Dependent Claim
259 words
An arrangemenT for controlling the direct current supplied from an alternating current source to a load across which it produces a reverse voltage comprising, at least one controlled rectifier connected in series with the load across said AC source, a control circuit by means of which the controlled rectifier is ignited during each forward half-cycle of the supply voltage with a controlled delay with respect to a reference instant at which the absolute value of a voltage proportional to said reverse voltage is equal to the instantaneous amplitude of the trailing edge of half a cycle of the supply voltage or of a voltage proportional thereto, so that, within certain limits, the effective current applied to the load is substantially independent of the reverse voltage produced across said load, and wherein said control circuit comprises a time-measuring circuit having a reset switch, the time-measuring circuit producing a pulse for igniting said controlled rectifier with a controlled time delay after the reference instant that is determined by the time-measuring circuit, a comparison circuit, means for applying to said comparison circuit the difference between the supply voltage and the reverse voltage, said comparison circuit including a voltage difference limiter followed by a differentiating circuit which produces pulses whenever the amplitude of the supply voltage is equal to the amplitude of the reverse voltage, and wherein the reset switch is controlled by the pulses derived from the differentiating circuit and is sensitive solely to control signals of a given polarity corresponding to that of the reset pulses corresponding to the reference instant.
Claim 3
Dependent Claim
92 words
An arrangement as claimed in claim 1 further comprising a second controlled rectifier for supplying energy to the load, said controlled rectifiers being included in a multiphase rectifier, characterized in that the comparison circuit comprises a number of branches equal to the number of phases, the difference between a corresponding phase of the alternating supply voltage and the reverse voltage being applied to each of said branches, said arrangement including a corresponding number of voltage limiters followed each by a corresponding differentiating circuit for controlling the reset switch of the time-measuring circuit.
Claim 4
Dependent Claim
46 words
An arrangement as claimed in claim 2 wherein the load is energized by means of said two controlled rectifiers connected as a full-wave rectifier, characterized in that the pulses produced by the two differentiating circuits are applied to the reset switch of a common time-measuring circuit.
Claim 5
Dependent Claim
150 words
An arrangement as claimed in claim 1 for feeding the load with a mean current of reversible direction comprising, a second controlled rectifier connected in circuit with the load and the first controlled rectifier so that there is one controlled rectifier for each current direction, characterized in that it comprises a time-measuring circuit having a reset switch for each current direction, one reset switch being exclusively responsive to the resetting pulses corresponding to the chosen reference instant and the other switch exclusively to the pulses of opposite polarity, and means for adjusting the respective time delays of the two time-measuring circuits differently so that the load is supplied with current pulses the respective durations of which differ from each other by the difference between the respective time delays, the direction of the mean load current then corresponding to the pass direction of the controlled rectifier ignited with the smaller delay.
Claim 6
Dependent Claim
43 words
An arrangement as claimed in claim 4 characterized in that it comprises a control circuit for simultaneously varying the time delays of both time-measuring circuits so that one time delay increases by the same amount by which the other decreases and vice versa.
Claim 7
Dependent Claim
35 words
An arrangement as claimed in claim 5 characterized in that the control circuit comprises a differential amplifier having two symmetrical outputs and two inputs to which a control voltage and a reFerence voltage are applied.
Claim 8
Dependent Claim
46 words
An arrangement as claimed in claim 5 wherein the load is a motor, said arrangement further comprising a protective circuit connected to the control circuit so that the maximum difference between the time delays of the two time-measuring circuits is reduced when the motor is overloaded.
Claim 9
Dependent Claim
41 words
An arrangement as claimed in claim 7 characterized in that the protective circuit is designed so that the time delays of the two time-measuring circuits are made larger than a half-cycle of the supply voltage in the case of motor overload.
Claim 10
Dependent Claim
98 words
An arrangement as claimed in claim 4 wherein the load is a commutator motor whose direction of rotation can be reversed by reversal of the direction of the rotor current, characterized in that the arrangement is designed so that the voltage drop across the rectifier circuit for one direction of rotation is equal to that across the rectifier circuit for the opposite direction of rotation, so that, with equal time delays, current pulses of alternating polarities and of equal duration are passed to the motor and the motor does not produce any driving torque at zero reverse voltage.
Claim 11
Dependent Claim
66 words
An arrangement as claimed in claim 4 further comprising an inductance connected in series with the controlled rectifiers and having a center tapping to which the load is connected whereby the AC component of the current supplied to the load is suppressed thereby to prevent a short circuit of the alternating voltage source in the event that two controlled rectifiers of opposite polarity are simultaneously conducting.
Claim 12
Dependent Claim
176 words
A circuit for supplying a direct current to a load from an alternating current supply source comprising, a controlled rectifier connecting said current source to the load to periodically energize the load during a forward half-cycle of the supply voltage whereby the load is of a type that develops a reverse voltage, and a control circuit coupled to the control electrode of the controlled rectifier to apply time-delayed ignition pulses thereto that control the firing angle of the controlled rectifier, said control circuit including a timing circuit that produces said ignition pulses for control of said firing angle, a reset switch coupled to the timing circuit and controlled by the reverse voltage of the load and the voltage of the supply source for resetting the timing circuit when the reverse voltage is equal to the voltage amplitude of the trailing edge of the forward half-cycle of the supply voltage, an increase in said reverse voltage being operative on said reset switch and in turn the timing circuit to advance the ignition point of the controlled rectifier.
Claim 13
Dependent Claim
176 words
A circuit for supplying a direct current to a load from an alternating current supply source comprising, a controlled rectifier connecting said current source to the load to periodically energize the load during a forward half-cycle of the supply voltage whereby the load is of a type that develops a reverse voltage, and a control circuit coupled to the control electrode of the controlled rectifier to apply time-delayed ignition pulses thereto that control the firing angle of the controlled rectifier, said control circuit including a timing circuit that produces said ignition pulses for control of said firing angle, a reset switch coupled to the timing circuit and controlled by the reverse voltage of the load and the voltage of the supply source for resetting the timing circuit when the reverse voltage is equal to the voltage amplitude of the trailing edge of the forward half-cycle of the supply voltage, an increase in said reverse voltage being operative on said reset switch and in turn the timing circuit to advance the ignition point of the controlled rectifier.
Claim 14
Dependent Claim
52 words
A circuit as claimed in claim 11 wherein the load is a motor and the timing circuit includes a resistor and capacitor connected across a source of constant voltage, said circuit further comprising a voltage threshold trigger element coupled between the RC timing circuit and the control electrode of the controlled rectifier.
Claim 15
Dependent Claim
49 words
A circuit as claimed in claim 12 further comprising means connecting the reset switch in parallel with the timing capacitor, the reset switch being normally open and being closed upon equality of the reverse voltage and said supply voltage trailing edge to provide a discharge path for the capacitor.
Claim 16
Dependent Claim
36 words
A circuit as claimed in claim 11 wherein the timing circuit includes a resistor and a capacitor connected across a source of constant voltage whereby the capacitor charge period is independent of the load reverse voltage.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-29 | 1975-05-31 | 1975-11-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-29 | 1979-05-31 | 1979-11-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-29 | 1983-05-31 | 1983-11-30 | $7700.00 | Window Closed / Lapsed |