Patent US3656038A successfully refreshed from Google Patents.
US3656038A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Field weakening circuit for a series field motor
Assignee: Schneider Electric USA Inc
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Filing: 1970-12-04
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Granted: 1972-04-11
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Expires: 1990-12-04
Abstract
Abstract In a control system for a direct current series motor, the contacts of a single throw reed relay are responsive to motor current through a winding in a motor supply conductor to selectively control the application of a motor field weakening shunt resistor by a switching circuit. The charging of a timing capacitor delays action of the switching circuit to prevent motor ''''hunting''''. The opening of the reed relay contacts under low motor load conditions permits charging of the capacitor and activating of the switching circuit to place the shunt resistor across the motor field for high speed operation. Under increased motor load, the reed relay contacts close and the capacitor discharges to time the removal of the shunt resistor from across the field. A by-pass transistor by-passes the reed relay contacts preventing activation of the switching circuit until the motor has reached its maximum unweakened field speed and the relay is provided with shunt windings to prevent ''''chattering'''' due to wavering motor current.
Inventors
- 👤 Robert G Ries
- 👤 Robert C Montross
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:53
CPC Classifications
H; H02; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/298
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
106 words
A control circuit for a direct current motor having an armature and a series field, said control circuit comprising field weakening means for controlling the strength of the field, a control means having a first operative condition, wherein said field weakening means is rendered operative to weaken the field, and a second operative condition, wherein said field weakening means permits the field to return to its normal strength, a switching means responsive to the magnitude of the motor current for determining the operative condition of said control means, and timing means for delaying response of said control means to the determining action of said switching means.
Claim 2
Dependent Claim
106 words
A control circuit for a direct current motor having an armature and a series field, said control circuit comprising field weakening means for controlling the strength of the field, a control means having a first operative condition, wherein said field weakening means is rendered operative to weaken the field, and a second operative condition, wherein said field weakening means permits the field to return to its normal strength, a switching means responsive to the magnitude of the motor current for determining the operative condition of said control means, and timing means for delaying response of said control means to the determining action of said switching means.
Claim 3
Dependent Claim
67 words
A control circuit in accordance with claim 1 wherein said timing means includes a capacitor and a charging circuit therefore, and said switching means has one operative condition in which the capacitor is permitted to charge through its charging circuit, and said control means includes voltage responsive means responsive to a predetermined voltage increase at the capacitor to effect said first operative condition of said control means.
Claim 4
Dependent Claim
35 words
A control circuit in accordance with claim 2 wherein said switching means includes means activated when said switching means is in said one operative condition for maintaining said switching means in said one operative condition.
Claim 5
Dependent Claim
28 words
A control circuit in accordance with claim 2 wherein said switching means has an other operative condition in which the charging circuit for the capacitor is rendered ineffective.
Claim 6
Dependent Claim
52 words
A control circuit in accordance with claim 4 wherein a discharge circuit for the capacitor is provided that becomes effective upon the charging circuit being rendered ineffective, and said voltage responsive means is responsive to a pre-determined voltage decrease at the capacitor to effect said second operative condition of the control means.
Claim 7
Dependent Claim
35 words
A control circuit in accordance with claim 4 wherein said switching means includes means activated when said switching means is in said other operative condition for maintaining said switching means in said other operative condition.
Claim 8
Dependent Claim
33 words
A control circuit in accordance with claim 4 wherein said switching means comprises contacts which are open in said one operative condition of the switching means and closed in said other operative condition.
Claim 9
Dependent Claim
19 words
A control circuit in accordance with claim 7 wherein said switching means is a reed relay including said contacts.
Claim 10
Dependent Claim
54 words
A control circuit in accordance with claim 4 including speed regulating means for said motor having a maximum speed setting, and by-pass means connected across said switching means and operable to maintain the second operative condition of said control means only when said speed regulating means is at less than the maximum speed setting.
Claim 11
Dependent Claim
30 words
A control circuit in accordance with claim 9 wherein said by-pass means comprises transistor means which, when biased into conduction, maintains the second operative condition of said first switching means.
Claim 12
Dependent Claim
27 words
A control circuit in accordance with claim 1 wherein said field weakening means comprises a resistor and relay means for selectably connecting the resistor across said field.
Claim 13
Dependent Claim
41 words
A control circuit in accordance with claim 1 wherein said control means comprises a first transistor means for controlling current through said relay means, and means connected to said timing means for establishing a biasing voltage for said second transistor means.
Claim 14
Dependent Claim
25 words
A control circuit in accordance with claim 12 wherein said control means includes threshold voltage responsive means connected between said first and second transistor means.
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) | 1975-04-11 | 1975-10-11 | 1976-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-04-11 | 1979-10-11 | 1980-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-04-11 | 1983-10-11 | 1984-04-11 | $7700.00 | Window Closed / Lapsed |