US3868549A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for protecting contacts against damage from arcing
Assignee: Franklin Electric Co Inc
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Filing: 1973-04-26
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Granted: 1975-02-25
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Expires: 1993-04-26
Abstract
Abstract This disclosure deals with a circuit for substantially reducing or eliminating switch contact damage due to arcing when opening or closing the switch contacts under heavy AC current load conditions. This is accomplished by providing a normally open shunt path across the contacts and momentarily closing the path at the instant of arcing. The shunt path includes contactless switch means which is normally open. Opening of the switch contacts effects turning on of the switch means and transfer of the load current thereto, thus quenching the arc. At the next subsequent zero crossing of the AC wave, the switch means is again opened. Similar operation occurs when the switch contacts close and an arc starts to develop due to contact bounce.
Inventors
- 👤 Edward J Schaefer
- 👤 August L Streater
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:58
CPC Classifications
H; H01; H01H; H01H9/00; H01H9/54; H01H9/541; H01H9/542; H01H2009/546
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
140 words
In a circuit including an alternating current supply, a load, and switch contacts connected to carry load current when closed and required to open under heavy current load conditions, the improvement comprising contactless switch means adapted to be connected to form a current path which bypasses said contacts, an electrical device adapted to be connected in series with said load and said contacts, said switch means including bias means connected to respond to current flow through said device and to a potential across said contacts, said switch means being biased to conduction only when a potential exists across said contacts and current flows through said device, whereby said switch means is biased to conduction and load current is transferred to said path from the time of initiation of an arc until the next subsequent zero crossing of the alternating current.
Claim 2
Dependent Claim
140 words
In a circuit including an alternating current supply, a load, and switch contacts connected to carry load current when closed and required to open under heavy current load conditions, the improvement comprising contactless switch means adapted to be connected to form a current path which bypasses said contacts, an electrical device adapted to be connected in series with said load and said contacts, said switch means including bias means connected to respond to current flow through said device and to a potential across said contacts, said switch means being biased to conduction only when a potential exists across said contacts and current flows through said device, whereby said switch means is biased to conduction and load current is transferred to said path from the time of initiation of an arc until the next subsequent zero crossing of the alternating current.
Claim 3
Dependent Claim
23 words
Apparatus as in claim 1, wherein said switch contacts and said device form a switch unit, and said device is a heater resistor.
Claim 4
Dependent Claim
61 words
Apparatus as in claim 1, wherein said switch means includes main terminals for carrying said load current and a control terminal for turning on said switch means, said main terminals being adapted to be connected to respond to a potential due to arcing, and said control terminal being connected to said device, said device providing energizing current to said control terminal.
Claim 5
Dependent Claim
11 words
Apparatus as in claim 3, wherein said device comprises a resistor.
Claim 6
Dependent Claim
12 words
Apparatus as in claim 3, wherein said device comprises a current transformer.
Claim 7
Dependent Claim
15 words
Apparatus as in claim 3, wherein said device comprises a potential transformer and a resistor.
Claim 8
Dependent Claim
24 words
Apparatus as in claim 3, wherein said device comprises an impedance and said main terminals are connected across both said contacts and said impedance.
Claim 9
Dependent Claim
19 words
Apparatus as in claim 3, wherein said power terminals are adapted to be connected directly across said switch contacts.
Claim 10
Dependent Claim
21 words
Apparatus as in claim 3, wherein said power terminals are adapted to be connected across Said switch contacts and said device.
Claim 11
Dependent Claim
14 words
Apparatus as in claim 1, wherein said switch means is a solid state device.
Claim 12
Dependent Claim
46 words
Apparatus as in claim 1, wherein said switch means comprises a TRIAC having two main terminals and a gate, said main terminals being adapted to be connected across said contacts and said gate being adapted to be connected to respond to current flow through said device.
Claim 13
Dependent Claim
32 words
Apparatus as in claim 1, and further including diode means connected in series with said switch means to prevent current flow through said switch means until said potential exceeds a minimum value.
Claim 14
Dependent Claim
13 words
Apparatus as in claim 12, wherein said diode means comprises a zener diode.
Claim 15
Dependent Claim
15 words
Apparatus as in claim 12, wherein said diode means comprises two back-to-back parallel connected diodes.
Claim 16
Dependent Claim
92 words
An AC power circuit comprising electrical contacts adapted to be connected to a load and an AC power supply, an electrical device connected in series with said load and said supply, contactless switch means connected to form a current path which bypasses said contacts and including bias means responsive to a potential across said contacts and to current flow through said device, whereby said switch means conducts only from the time of opening of said contacts and initiation of an arc and until the next subsequent zero crossing of the alternating current.
Claim 17
Dependent Claim
92 words
An AC power circuit comprising electrical contacts adapted to be connected to a load and an AC power supply, an electrical device connected in series with said load and said supply, contactless switch means connected to form a current path which bypasses said contacts and including bias means responsive to a potential across said contacts and to current flow through said device, whereby said switch means conducts only from the time of opening of said contacts and initiation of an arc and until the next subsequent zero crossing of the alternating current.
Claim 18
Dependent Claim
17 words
Apparatus as in claim 15, and further including diode means connected in series with said switch means.
Claim 19
Dependent Claim
36 words
Apparatus as in claim 16, wherein said device comprises resistance means connected in series with said contacts, said switch means comprising a TRIAC having its gate connected to respond to current flow through said resistance means.
Claim 20
Dependent Claim
16 words
Apparatus as in claim 17, wherein said contacts and said resistance means form an overload switch.
Claim 21
Dependent Claim
11 words
Apparatus as in claim 16, wherein said device comprises a resistor.
Claim 22
Dependent Claim
12 words
Apparatus as in claim 16, wherein said device comprises a current transformer.
Claim 23
Dependent Claim
15 words
Apparatus as in claim 16, wherein said device comprises a potential transformer and a resistor.
Claim 24
Dependent Claim
19 words
Apparatus as in claim 16, wherein said switch means is adapted to be connected directly across said switch contacts.
Claim 25
Dependent Claim
21 words
Apparatus as in claim 16, wherein said switch means is adapted to be connected across said switch contacts and said device.
Claim 26
Dependent Claim
116 words
An AC power circuit for an electric motor, comprising a motor winding, overload switch contacts and a device mounted within said motor, said winding and said contacts and said device being connected in series and being adapted to be connected to an AC power supply, switch means mounted within said motor and connected to form a bypass current path around said contacts, said switch means including bias means responsive to a potential across said contacts and to current flow through said winding and said device, whereby said switch means is biased to conduction by a potential due to the initiation of an arc and continues to conduct until the next zero crossing of the AC wave.
Claim 27
Dependent Claim
116 words
An AC power circuit for an electric motor, comprising a motor winding, overload switch contacts and a device mounted within said motor, said winding and said contacts and said device being connected in series and being adapted to be connected to an AC power supply, switch means mounted within said motor and connected to form a bypass current path around said contacts, said switch means including bias means responsive to a potential across said contacts and to current flow through said winding and said device, whereby said switch means is biased to conduction by a potential due to the initiation of an arc and continues to conduct until the next zero crossing of the AC wave.
Claim 28
Dependent Claim
23 words
Apparatus as in claim 24, wherein said switch means comprises a TRIAC, and further including diode means connected in series with said TRIAC.
Claim 29
Dependent Claim
16 words
Apparatus as in claim 24, wherein said device comprises a heater for heating said overload switch.
Claim 30
Dependent Claim
126 words
A circuit for preventing damage to switch contacts when opening under heavy current load conditions, comprising an electrical component adapted to be connected in series with said contacts and a load, voltage and current responsive switch means adapted to be connected to form a bypass current path around said contacts, said switch means including main terminals adapted to be connected across said contacts and a control terminal connected across said component, said switch means being biased to conduction only when a potential exists across said contacts due to arcing and when current flows through said component, whereby said current load is transferred from said contacts to said switch means from the initiation of an arc And until the next subsequent zero crossing of the alternating current.
Claim 31
Dependent Claim
126 words
A circuit for preventing damage to switch contacts when opening under heavy current load conditions, comprising an electrical component adapted to be connected in series with said contacts and a load, voltage and current responsive switch means adapted to be connected to form a bypass current path around said contacts, said switch means including main terminals adapted to be connected across said contacts and a control terminal connected across said component, said switch means being biased to conduction only when a potential exists across said contacts due to arcing and when current flows through said component, whereby said current load is transferred from said contacts to said switch means from the initiation of an arc And until the next subsequent zero crossing of the alternating current.
Claim 32
Dependent Claim
19 words
Apparatus as in claim 6, wherein said main terminals are connected across both said contacts and said current transformer.
Claim 33
Dependent Claim
15 words
Apparatus as in claim 6, wherein said main terminals are connected across said contacts only.
Claim 34
Dependent Claim
130 words
In a power circuit including an AC power supply, a load connected to be energized by said supply, and switch contacts connected in series with said supply and said load for controlling the flow of current to said load, the improvement of means for preventing arcing across said contacts during opening under heavy load current conditions, comprising an electrical component connected in series with said contacts and said load, a triac including main terminals and a gate, said main terminals being connected in said power circuit to form a current path around said contacts, and said gate being connected to said component, whereby said triac is turned on when opening of said contacts produces a potential across said main terminals and current flow through said component provides gate triggering current.
Claim 35
Dependent Claim
130 words
In a power circuit including an AC power supply, a load connected to be energized by said supply, and switch contacts connected in series with said supply and said load for controlling the flow of current to said load, the improvement of means for preventing arcing across said contacts during opening under heavy load current conditions, comprising an electrical component connected in series with said contacts and said load, a triac including main terminals and a gate, said main terminals being connected in said power circuit to form a current path around said contacts, and said gate being connected to said component, whereby said triac is turned on when opening of said contacts produces a potential across said main terminals and current flow through said component provides gate triggering current.
Claim 36
Dependent Claim
37 words
In a power circuit as in claim 30, wherein said main terminals are connected directly across said contacts, said component is a resistor, and said gate triggering current is in phase with the voltage across said resistor.
Claim 37
Dependent Claim
34 words
In a power circuit as in claim 30, wherein said main terminals are connected across both said contacts and said component, whereby current flow through said triac bypasses both said contacts and said component.
References Cited (Backward Citations)
US3474293A
Cited
US3555353A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-24 | 1978-08-26 | 1979-02-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-24 | 1982-08-26 | 1983-02-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-24 | 1986-08-26 | 1987-02-25 | $7700.00 | Window Closed / Lapsed |