US3811080A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control circuits for d.c. electric motors
Assignee: Cableform Ltd
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Filing: 1972-04-24
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Granted: 1974-05-14
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Expires: 1992-04-24
Abstract
Abstract In control circuits for controlling D.C. electric motors, the motor is supplied in pulses so that the mean power supplied to the motor is varied by varying the frequency and/or mark-space ratio of the generator pulses. In such arrangements electrical braking is obtained by reversing the field winding connections but the field current has to be kept relatively low even for heavy braking. In the present invention means are provided for ascertaining if the armature current exceeds the field current during each pulse of current and for restricting the range of current which can be applied to the motor if the armature current exceeds the field current by a predetermined amount.
Inventors
- 👤 J Morton
- 👤 K Stevens
- 👤 G Thexton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:20
CPC Classifications
H; H02; H02P; H02P3/00; H02P3/06; H02P3/08; H02P3/10
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
153 words
A control circuit for controlling a D.C. electric motor having an armature and a field and a diode connected across the armature so as to be in reverse bias polarity when the motor is in drive condition, comprising a D.C. switch which provides pulses of current from a D.C. source to the motor, which pulses vary in frequency and/or mark-space ratio in accordance with a control signal, a capacitor which commences charging at the beginning of each current pulse and is discharged by switching means which is conductive when the diode across the armature is reverse biassed, and means for ascertaining, during each pulse, if the charge on the capacitor reaches a predetermined level, the arrangement being such that a full range of current may be applied to the motor if the predetermined level is not reached and only a restricted range of current may be applied if the predetermined level is reached.
Claim 2
Dependent Claim
153 words
A control circuit for controlling a D.C. electric motor having an armature and a field and a diode connected across the armature so as to be in reverse bias polarity when the motor is in drive condition, comprising a D.C. switch which provides pulses of current from a D.C. source to the motor, which pulses vary in frequency and/or mark-space ratio in accordance with a control signal, a capacitor which commences charging at the beginning of each current pulse and is discharged by switching means which is conductive when the diode across the armature is reverse biassed, and means for ascertaining, during each pulse, if the charge on the capacitor reaches a predetermined level, the arrangement being such that a full range of current may be applied to the motor if the predetermined level is not reached and only a restricted range of current may be applied if the predetermined level is reached.
Claim 3
Dependent Claim
47 words
A control circuit as claimed in claim 1, wherein the discharge switching means comprises a transistor connected across said capacitor, the base emitter circuit of the transistor being included in the output circuit of a second transistor whose base emitter circuit is connected across the armature diode.
Claim 4
Dependent Claim
36 words
A control circuit as claimed in claim 1, wherein said capacitor is in series with a charging resistor in the output circuit of a transistor to the base of which the pUlse control signal is applied.
Claim 5
Dependent Claim
45 words
A control circuit as claimed in claim 1, wherein the means for ascertaining if the charge on the capacitor reaches a predetermined level comprises a Zenner diode which becomes conductive when the voltage across the capacitor reaches the threshold breakdown voltage of the Zenner diode.
Claim 6
Dependent Claim
40 words
A control circuit as claimed in claim 4, wherein, whilst the Zenner diode is conductive, a clamp in a pulse generator which produces the control signal, is operative to restrict the frequency range of the pulses in the control signal.
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) | 1977-05-13 | 1977-11-12 | 1978-05-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-13 | 1981-11-12 | 1982-05-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-13 | 1985-11-12 | 1986-05-14 | $7700.00 | Window Closed / Lapsed |