US3761794A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electric motor control circuits
Assignee: Delta International Machinery Corp
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Filing: 1973-02-16
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Granted: 1973-09-25
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Expires: 1993-02-16
Abstract
Abstract An electric motor control circuit having an interlocking relay which is connected in the motor field winding circuit for energization by the voltage applied to at least part of one motor field winding to close a set of normally open relay contacts that complete a holding circuit around a motor start switch. The interlocking relay is connected in series with a set of normally closed motor overload contacts between the motor input terminals so that opening of the motor overload contacts or a power failure de-energizes the interlocking relay. De-energization of the interlocking relay opens the relay contacts to de-energize a motor starting contactor for disconnecting the motor field circuit from the line.
Inventors
- 👤 A Sinagra
- 👤 J Quinlisk
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 08:38
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/08; H02H7/085; H02H7/0852; H02H11/00
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
378 words
In combination with an a.c. electric motor having at least a pair of input terminals, at least one field winding and an automatically resettable motor overload protective device that includes a set of normally closed overload contacts, said overload contacts being connected in series with said field winding between said terminals and opening upon the occurrence of a motor overload cOndition to interrupt the energizing circuit for said field winding, a motor control circuit comprising a motor starting contactor having a coil and normally open contacts for connecting said terminals to a source of alternating current, a selectively actuatable normally open astable motor start switch, a selectively actuatable normally closed motor stop switch, said start switch, said stop switch and said contactor coil being connected in series across a current supply source to provide for the energization of said coil upon closure of said start switch, said contactor being effective upon energization of said coil to close said normally open contacts to complete a circuit through said overload contacts for energizing said field winding, and a relay connected between said terminals in series with said overload contacts and in parallel with at least a part of said field winding for energization by the voltage applied to said field winding when the normally open contacts of said contactor are closed to complete the circuit for energizing said field winding, said relay having a set of normally open relay contacts in parallel with said start switch and in series with said stop switch and said contactor coil, said relay being effective upon energization to close its normally open relay contacts to complete a holding circuit for maintaining said contactor coil energized after said start switch is released to its normally open position, and said relay being de-energized by the opening of said overload contacts or by a failure of the power supply from said alternating current source to open its set of normally open contacts, said set of normally open relay contacts being effective upon opening to de-energize said coil, said contactor being effective upon de-energization of said coil to open its normally open contacts, thereby requiring said start switch to selectively be momentarily closed in order to recomplete the circuit between said terminals and said source of alternating current.
Claim 2
Dependent Claim
378 words
In combination with an a.c. electric motor having at least a pair of input terminals, at least one field winding and an automatically resettable motor overload protective device that includes a set of normally closed overload contacts, said overload contacts being connected in series with said field winding between said terminals and opening upon the occurrence of a motor overload cOndition to interrupt the energizing circuit for said field winding, a motor control circuit comprising a motor starting contactor having a coil and normally open contacts for connecting said terminals to a source of alternating current, a selectively actuatable normally open astable motor start switch, a selectively actuatable normally closed motor stop switch, said start switch, said stop switch and said contactor coil being connected in series across a current supply source to provide for the energization of said coil upon closure of said start switch, said contactor being effective upon energization of said coil to close said normally open contacts to complete a circuit through said overload contacts for energizing said field winding, and a relay connected between said terminals in series with said overload contacts and in parallel with at least a part of said field winding for energization by the voltage applied to said field winding when the normally open contacts of said contactor are closed to complete the circuit for energizing said field winding, said relay having a set of normally open relay contacts in parallel with said start switch and in series with said stop switch and said contactor coil, said relay being effective upon energization to close its normally open relay contacts to complete a holding circuit for maintaining said contactor coil energized after said start switch is released to its normally open position, and said relay being de-energized by the opening of said overload contacts or by a failure of the power supply from said alternating current source to open its set of normally open contacts, said set of normally open relay contacts being effective upon opening to de-energize said coil, said contactor being effective upon de-energization of said coil to open its normally open contacts, thereby requiring said start switch to selectively be momentarily closed in order to recomplete the circuit between said terminals and said source of alternating current.
Claim 3
Dependent Claim
55 words
The combination defined in claim 1 wherein said contactor further includes an auxiliary set of normally open contacts connected in series with said relay and in parallel with said field winding to prevent energization of said relay by any back emf that may be developed after said motor is disconnectd from said alternating current source.
Claim 4
Dependent Claim
40 words
The combination defined in claim 1 wherein said motor is a single phase motor, wherein said one field winding is a running winding, and wherein said motor further includes a start field winding connected in series with said overload contacts.
Claim 5
Dependent Claim
30 words
The combination defined in claim 3 wherein start and running windings are connected in parallel circuit relationship, said relay being in parallel with both of said start and running windings.
Claim 6
Dependent Claim
29 words
The combination defined in claim 3 wherein said start and running windings are connected in series circuit relationship, and wherein said relay is in series with said start winding.
Claim 7
Dependent Claim
45 words
The combination defined in claim 1 wherein said motor is a three phase motor having a Y-connection that provides three legs, with each leg containing at least one field winding, and wherein said relay is connected across the field winding in one of said legs.
Claim 8
Dependent Claim
39 words
The combination defined in claim 1 wherein the current supply source across which said switches and said coil are connected is a secondary winding of a step-down transformer having a primary winding connected to said source of alternating current.
Claim 9
Dependent Claim
270 words
In combination with an a.c. electric motor having input terminals, and a field winding circuit that is connected to said terminals and that includes at least one field winding, a motor control circuit comprising a contactor having normally open contactor contacts which upon closing connect said field winding circuit to a source of alternating current for energizing said field winding circuit, a selectively actuatable normally open astable motor start switch, a selectively actuatable normally closed motor stop switch, a coil fOrming a part of said contactor, said switches and said coil being connected in series across a current source to provide for the energization of said coil upon closing said start switch, said contactor being effective upon energization of said coil to close said normally open contactor contacts, and a relay connected in said field winding circuit in parallel with said one field winding to be energized by the voltage that is applied across said field winding upon energizing said field winding circuit, said relay having a set of normally open contacts connected in parallel with said start switch and in series with said coil and said stop switch, said relay being effective upon energization to close said relay contacts for completing a holding circuit that maintains said coil energized when said start switch is opened after being closed, said relay being de-energized when said field winding circuit is de-energized to open said relay contacts and thereby interrupt said holding circuit to de-energize said coil, said contactor being effective upon de-energization of said coil to open said contactor contacts to disconnect said field winding circuit from said alternating current source.
Claim 10
Dependent Claim
270 words
In combination with an a.c. electric motor having input terminals, and a field winding circuit that is connected to said terminals and that includes at least one field winding, a motor control circuit comprising a contactor having normally open contactor contacts which upon closing connect said field winding circuit to a source of alternating current for energizing said field winding circuit, a selectively actuatable normally open astable motor start switch, a selectively actuatable normally closed motor stop switch, a coil fOrming a part of said contactor, said switches and said coil being connected in series across a current source to provide for the energization of said coil upon closing said start switch, said contactor being effective upon energization of said coil to close said normally open contactor contacts, and a relay connected in said field winding circuit in parallel with said one field winding to be energized by the voltage that is applied across said field winding upon energizing said field winding circuit, said relay having a set of normally open contacts connected in parallel with said start switch and in series with said coil and said stop switch, said relay being effective upon energization to close said relay contacts for completing a holding circuit that maintains said coil energized when said start switch is opened after being closed, said relay being de-energized when said field winding circuit is de-energized to open said relay contacts and thereby interrupt said holding circuit to de-energize said coil, said contactor being effective upon de-energization of said coil to open said contactor contacts to disconnect said field winding circuit from said alternating current source.
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) | 1976-09-24 | 1977-03-26 | 1977-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-24 | 1981-03-26 | 1981-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-24 | 1985-03-26 | 1985-09-25 | $7700.00 | Window Closed / Lapsed |