US3903456A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Protector system for an electric motor
Assignee: Franklin Electric Co Inc
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Filing: 1974-01-28
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Granted: 1975-09-02
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Expires: 1994-01-28
Abstract
Abstract This disclosure deals with a protection circuit for an electric motor, the motor being connected by power lines to a power supply. A thermal protector switch is connected in at least one of the lines and is mounted closely adjacent at least one of the windings of the motor, and a main contactor is connected in the lines to control the flow of power to the motor. The circuit includes means for responding to the opening of the protector switch by sensing the absence of current flow in the power line to which it is connected, and for actuating the main contactor to open the power lines. The protection circuit further includes means for preventing automatic reapplication of power to the motor even though the protector switch is automatically resettable, thereby requiring manual resetting of the circuit. In the case of a three phase motor, the circuit enables the use of a single protector switch thereby avoiding problems due to random resetting of plural protection switches.
Inventors
- 👤 Edward J Schaefer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 07:53
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/08; H02H7/085; H02H7/0856; H02H7/0859; H02H7/0852
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
124 words
A system for protecting an electric motor including at least one winding connected to a power supply by a plurality of power lines, said system comprising a thermal protector switch adapted to be connected in a selected line, said switch further being mounted in heat exchange relation with said winding, a contactor connected in said power lines for controlling the application of power to said motor, and current sensing circuit means coupled to at least one of said power lines including said selected line for sensing the presence or absence of current flow therethrough, said current sensing circuit means being connected to said contactor and actuating said contactor to open said power lines in the absence of current flow through said one power line.
Claim 2
Independent Claim
124 words
A system for protecting an electric motor including at least one winding connected to a power supply by a plurality of power lines, said system comprising a thermal protector switch adapted to be connected in a selected line, said switch further being mounted in heat exchange relation with said winding, a contactor connected in said power lines for controlling the application of power to said motor, and current sensing circuit means coupled to at least one of said power lines including said selected line for sensing the presence or absence of current flow therethrough, said current sensing circuit means being connected to said contactor and actuating said contactor to open said power lines in the absence of current flow through said one power line.
Claim 3
Independent Claim
195 words
A system for protecting an electric motor including at least one winding connected to a power supply by a plurality of power lines, said system comprising a thermal protector switch adapted to be connected in a selected line, said switch further being mounted in heat exchange relation with said winding, a contactor connected in said power lines for controlling the application of power to said motor, and current sensing circuit means coupled to at least one of said power lines including said selected line for sensing the presence or absence of current flow therethrough, said current sensing circuit means being connected to said contactor and actuating said contactor to open said power lines in the absence of current flow through said one power line, said contactor including a coil, and said current sensing circuit means including control contacts which are actuated by current flow through said power lines, switch contacts, means serially connecting said control contacts, said switch contacts and said contactor coil to a power supply, and timing means connected across said control contacts for momentarily enabling current fLow through said coil when said switch contacts are closed and said control contacts are open.
Claim 4
Independent Claim
195 words
A system for protecting an electric motor including at least one winding connected to a power supply by a plurality of power lines, said system comprising a thermal protector switch adapted to be connected in a selected line, said switch further being mounted in heat exchange relation with said winding, a contactor connected in said power lines for controlling the application of power to said motor, and current sensing circuit means coupled to at least one of said power lines including said selected line for sensing the presence or absence of current flow therethrough, said current sensing circuit means being connected to said contactor and actuating said contactor to open said power lines in the absence of current flow through said one power line, said contactor including a coil, and said current sensing circuit means including control contacts which are actuated by current flow through said power lines, switch contacts, means serially connecting said control contacts, said switch contacts and said contactor coil to a power supply, and timing means connected across said control contacts for momentarily enabling current fLow through said coil when said switch contacts are closed and said control contacts are open.
Claim 5
Dependent Claim
19 words
A system as in claim 2, wherein said timing device comprises a PTC resistor connected across said control contacts.
Claim 6
Dependent Claim
28 words
A system as in claim 2, wherein said timing device comprises a PTC resistor, said control contacts being connected across both said PTC resistor and said switch contacts.
Claim 7
Dependent Claim
54 words
A system as in claim 1, wherein said thermal protector switch includes normally closed contacts, and further including a TRIAC connected across said normally closed contacts, and means connected in series with said contacts and responsive to current flow through said contacts for turning said TRIAC momentarily on when said normally closed contacts open.
Claim 8
Dependent Claim
45 words
A system as in claim 1, wherein said current sensing means comprises a control relay including a coil and control contacts, said coil being formed by a loop in said selected power line, and said control contacts being connected to control operation of said contactor.
Claim 9
Dependent Claim
45 words
A system as in claim 1, wherein said current sensing means comprises a current transformer including a primary winding and a secondary winding, said primary winding being connected in said selected power line, and said secondary winding being connected to control operation of said contactor.
Claim 10
Dependent Claim
32 words
A system as in claim 1, wherein said motor is a three phase motor and there are three power lines, and said current sensing means is coupled to all three power lines.
Claim 11
Dependent Claim
79 words
A system as in claim 8, wherein said current sensing means comprises a loop formed in each of said lines, each of said loops being magnetically coupled to a relay plunger which actuates a normally open set of relay contacts, said relay contacts being connected in series and connected to said contactor, whereby the circuit to said contactor is closed only when current flows through all three of said power lines and closes all of said sets of contacts.
Claim 12
Dependent Claim
49 words
A system as in claim 8, wherein said current sensing means comprises a current transformer for each of said lines, each transformer including a primary winding connected in a power line and a secondary winding, the secondary windings of said transformers being connected to control operation of said contactor.
Claim 13
Dependent Claim
44 words
A system as in claim 10, wherein said secondary windings are connected to an AND gate, a relay coil being connected to the output of said AND gate and said coil being energized only when current is induced in each of said secondary windings.
Claim 14
Dependent Claim
43 words
A system as in claim 10, wherein said secondary windings are connected to the three windings of a miniature three phase motor, said miniature motor including a movable element which controls operation of a relay, and said relay controlling operation of said contactor.
Claim 15
Dependent Claim
129 words
A circuit for use with an electric motor connected to a power supply by power lines, the circuit including an automatically resettable thermal protector switch connected in a selected one of the lines and mounted in heat exchange relation with a motor winding, current sensing means coupled to at least one of said lines including said selected power line for sensing the presence or absence of current flow therethrough, a main contactor connected in said power lines for controlling the application of power to said motor, said current sensing means being connected to said contactor for actuating said contactor to open said lines in the absence of current flow through said selected of said lines and means for preventing automatic reenergization of the motor after opening of said switch.
Claim 16
Dependent Claim
129 words
A circuit for use with an electric motor connected to a power supply by power lines, the circuit including an automatically resettable thermal protector switch connected in a selected one of the lines and mounted in heat exchange relation with a motor winding, current sensing means coupled to at least one of said lines including said selected power line for sensing the presence or absence of current flow therethrough, a main contactor connected in said power lines for controlling the application of power to said motor, said current sensing means being connected to said contactor for actuating said contactor to open said lines in the absence of current flow through said selected of said lines and means for preventing automatic reenergization of the motor after opening of said switch.
Claim 17
Dependent Claim
166 words
A protector circuit for protecting a three phase load against damage, three power lines being provided to connect said load to a three phase power supply, comprising automatically resetable thermal protector means connected in one of said lines and mounted in heat exchange relation with said load, power contactor means adapted to be connected in said three power lines for simultaneously opening or closing said Lines, said contactor means including electrically responsive means for actuating said contactor to open or close said lines, control circuit means connected to said responsive means and electrically coupled to at least one of said three power lines, said control circuit means responding to current flow through said three power lines and actuating said contactor means to open said lines when current ceases to flow through said lines, reset switch means in said control circuit for actuating said contactor to close said lines, and timing means in said control circuit enabling resetting of said contactor means but preventing automatic resetting thereof.
Claim 18
Dependent Claim
166 words
A protector circuit for protecting a three phase load against damage, three power lines being provided to connect said load to a three phase power supply, comprising automatically resetable thermal protector means connected in one of said lines and mounted in heat exchange relation with said load, power contactor means adapted to be connected in said three power lines for simultaneously opening or closing said Lines, said contactor means including electrically responsive means for actuating said contactor to open or close said lines, control circuit means connected to said responsive means and electrically coupled to at least one of said three power lines, said control circuit means responding to current flow through said three power lines and actuating said contactor means to open said lines when current ceases to flow through said lines, reset switch means in said control circuit for actuating said contactor to close said lines, and timing means in said control circuit enabling resetting of said contactor means but preventing automatic resetting thereof.
Claim 19
Dependent Claim
131 words
An electric motor and protection circuit, comprising an electric motor including at least one winding adapted to be connected to a power supply by a plurality of power lines, a thermal protector switch mounted in said motor in heat exchange relation with said winding, said switch being connected in one of said power lines, a contactor connected in said power lines for controlling the application of power to said motor, and current sensing circuit means coupled to said one power line and responding to operation of said switch by sensing the presence or absence of current flow through said one line, said current sensing circuit means being connected to said contactor and actuating said contactor to open said power lines in the absence of current flow through said one power line.
Claim 20
Dependent Claim
131 words
An electric motor and protection circuit, comprising an electric motor including at least one winding adapted to be connected to a power supply by a plurality of power lines, a thermal protector switch mounted in said motor in heat exchange relation with said winding, said switch being connected in one of said power lines, a contactor connected in said power lines for controlling the application of power to said motor, and current sensing circuit means coupled to said one power line and responding to operation of said switch by sensing the presence or absence of current flow through said one line, said current sensing circuit means being connected to said contactor and actuating said contactor to open said power lines in the absence of current flow through said one power line.
References Cited (Backward Citations)
US3588605A
Cited
US3761794A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-01 | 1979-03-03 | 1979-09-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-01 | 1983-03-03 | 1983-09-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-01 | 1987-03-03 | 1987-09-02 | $7700.00 | Window Closed / Lapsed |