US3875464A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Solid state overload relay
Assignee: Westinghouse Electric Corp
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Filing: 1973-10-10
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Granted: 1975-04-01
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Expires: 1993-10-10
Abstract
Abstract An electronic overload relay connectable in series with the operating coil of a contactor for protecting a motor from overheating due to carrying greater than desired current. The disclosed overload relay includes a time delayed reset feature which does not require control power to provide the delayed reset. The delayed reset prevents an operator from restarting a motor before it has cooled off by interrupting power to the overload relay and then reapplying power. The time delayed reset includes means for transferring energy stored in the sensing and tripping portions during the overload period to an energy storage device which prevents power from being reapplied to the electric motor until a predetermined time after the overload relay has tripped. The transferred energy is discharged through a timing resistor until a predetermined point is reached at which time the overload relay can be again closed. A light emitting diode is provided to indicate that the overload relay is in the tripped mode and power cannot be applied to the protected motor. Operation of the overload trip relay is unaffected by connecting or disconnecting power to the motor during normal operation.
Inventors
- 👤 Wardell Gary
- 👤 Emroy W Lange
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 19:16
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/02; H02H3/06; H02H7/00; H02H7/08; H02H7/085
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
274 words
An electronic overload relay connectable in series with the operating coil of a contactor for protecting a motor from overheating due to carrying greater than selected current comprising: an output contact connected in series with the contactor coil being switchable between a high resistance level where current flows through the coil as limited and the contactor is unenergized and a low resistance level where there is sufficient current flow through the coil to energize the contactor; output contact trigger means connected to said output contact for switching said output contact to the high resistance level or the low resistance level; current sensing means connected to sense motor current and to supply an output signal proportional to motor current; time delay means connected between said output contact trigger means and said current sensing means and being responsive to the level of the output signal from said current sensing means to energize said output contact trigger means after a time delay only when a current greater than a selected current flows to the motor; said output contact trigger means being constructed to switch said output contact to the high resistance level when energized from said time delay means; said output contact trigger means comprises a first energy storage means for storing energy when said output contact trigger means is energized from said time delay means and being connected to keep said output contact trigger means energized for a predetermined time after the energizing signal from said time delay is removed without requiring any external power thus maintaining said output contact at the high resistance level and preventing the contactor from being energized for the predetermined time.
Claim 2
Dependent Claim
274 words
An electronic overload relay connectable in series with the operating coil of a contactor for protecting a motor from overheating due to carrying greater than selected current comprising: an output contact connected in series with the contactor coil being switchable between a high resistance level where current flows through the coil as limited and the contactor is unenergized and a low resistance level where there is sufficient current flow through the coil to energize the contactor; output contact trigger means connected to said output contact for switching said output contact to the high resistance level or the low resistance level; current sensing means connected to sense motor current and to supply an output signal proportional to motor current; time delay means connected between said output contact trigger means and said current sensing means and being responsive to the level of the output signal from said current sensing means to energize said output contact trigger means after a time delay only when a current greater than a selected current flows to the motor; said output contact trigger means being constructed to switch said output contact to the high resistance level when energized from said time delay means; said output contact trigger means comprises a first energy storage means for storing energy when said output contact trigger means is energized from said time delay means and being connected to keep said output contact trigger means energized for a predetermined time after the energizing signal from said time delay is removed without requiring any external power thus maintaining said output contact at the high resistance level and preventing the contactor from being energized for the predetermined time.
Claim 3
Dependent Claim
55 words
An electronic overload relay as claimed in claim 1 including: tripped indicator means connected to said output contact trigger means for indicating when said output contact is switched to the high resistance level; and, said tripped indicator means comprises a light source which lights when said output contact is switched to the high resistance level.
Claim 4
Dependent Claim
18 words
An electronic overload relay as claimed in claim 2 wherein: said light source comprises a light emitting diode.
Claim 5
Dependent Claim
52 words
An electronic overload relay as claimed in claim 1 including: rating adjustment means connected between said current sensing means and said time delay means for varying the level of the output signal from said current sensing means to change the selected current level at which said output contact trigger means is energized.
Claim 6
Dependent Claim
89 words
An electronic overload relay as claimed in claim 1 wherein: said time delay means has an inverse time output signal characteristic so that the time delay after which said output contact trigger means is energizes is a function of the current flow to the motor; and including, rating adjustment means connected between said current sensing means and said time delay means for varying the level of the output signal from said current sensing means to change the selected current level at which said output contact trigger means is energized.
Claim 7
Dependent Claim
55 words
An electronic overload relay as claimed in claim 5 comprising: tripped indicator means connected to said output contact trigger means for indicating when said output contact is switched to the high resistance level; and, said tripped indicator means comprises a light source which light when said output contact is switched to the high resistance level.
Claim 8
Dependent Claim
83 words
An electronic overload relay as claimed in claim 5 wherein: said time delay means comprise turn-off trigger means connected to said output contact trigger means and a timing capacitor circuit which is charged from the output signal from said current sensing means; and, said turn-off trigger circuit means connected to said timing capacitor and being responsive to the voltage level of said timing capacitor to energize said output contact trigger means when the voltage level on said timing capacitor exceeds a predetermined point.
Claim 9
Dependent Claim
77 words
An electronic overload relay as claimed in claim 7 wherein: said turn off trigger means comprises a programmable unijunction transistor; including, low level direct current supply means being powered from said current sensing means and connected to said turn-off trigger means for supplying a reference voltage; and, said low level direct current supply means comprises a second energy storage means which transfers energy to said first energy storage means when said output contact trigger means is energized.
Claim 10
Dependent Claim
81 words
An electronic overload relay as claimed in claim 8 comprising; high voltage level filter means connected to the output of said rating adjustment for smoothing the output signal; and, trip level switch means connected between said high voltage level filter means and said time delay means and controlling the voltage level supplied to said timing capacitor from a first level less than the reference voltage to a second level greater than the reference voltage and a function of the output signal.
Claim 11
Dependent Claim
212 words
A solid statE overload relay connectable in series with the coil of a motor contactor for protecting the motor from overload currents comprising: output contact means switchable between a first state wherein the coil can be energized and a second state wherein the coil cannot be energized; output contact trigger means, connected to said output contact means for switching said output contact means to the first state or the second state, comprising first capacitive stored energy means for maintaining said output contact means in a second state when charged above a predetermined trip level; current sensing means connected to sense motor current and to supply an output signal proportional to motor current; trip means connected between said current sensing means and said output trigger means comprising a second capactive stored energy means and a time delay means; said second capacitive stored energy means being charged rapidly to a predetermined level when the motor contactor is closed; said time delay means connected to permit energy to flow from said second capacitive stored energy means to said first capacitive stored energy means, raising said first stored energy means above the predetermined trip level and maintaining said output contact means in a second state, a time delayed period after motor current exceeds a predetermined value.
Claim 12
Dependent Claim
212 words
A solid statE overload relay connectable in series with the coil of a motor contactor for protecting the motor from overload currents comprising: output contact means switchable between a first state wherein the coil can be energized and a second state wherein the coil cannot be energized; output contact trigger means, connected to said output contact means for switching said output contact means to the first state or the second state, comprising first capacitive stored energy means for maintaining said output contact means in a second state when charged above a predetermined trip level; current sensing means connected to sense motor current and to supply an output signal proportional to motor current; trip means connected between said current sensing means and said output trigger means comprising a second capactive stored energy means and a time delay means; said second capacitive stored energy means being charged rapidly to a predetermined level when the motor contactor is closed; said time delay means connected to permit energy to flow from said second capacitive stored energy means to said first capacitive stored energy means, raising said first stored energy means above the predetermined trip level and maintaining said output contact means in a second state, a time delayed period after motor current exceeds a predetermined value.
Claim 13
Dependent Claim
42 words
A solid state overload relay as claimed in claim 10, comprising: a light emitting diode connected to be energized when said first capacitive stored energy means is charged above a predetermined level indicating said output contact means is in the second state.
Claim 14
Dependent Claim
56 words
A solid state overload relay as claimed in claim 10, wherein; said time delay means constructed to disconnect said first capacitive stored energy means from said second capacitive stored energy means, after they have been connected due to motor current exceeding a predetermined value, when the voltage levels of both capacitive stored energy means have equalized.
Claim 15
Dependent Claim
40 words
A solid state overload relay as claimed in claim 10, compising: activating means connected to switch said output contact means to the first state at predetermined intervals unless said first stored energy means is raised above the predetermined trip level.
Claim 16
Dependent Claim
37 words
A solid state overload relay as claimed in claim 10, comprising: energy dissipation means connected to said first capacitive stored energy means for draining off energy from said first capacitive stored energy means at a determinable rate.
Claim 17
Dependent Claim
33 words
A solid state overload relay as claimed in claim 10, comprising: trip level adjustment means connected to said trip means for changing the current level above which said time delay means is activated.
Claim 18
Dependent Claim
174 words
A solid state overload relay for controlling electric power to a motor comprising: current transformer means for indicating the current flow to the motor; first capacitive energy storage means connected to said current transformer for rapidly storing energy when electric power is connected to the motor; motor disconnecting means for disconnecting the motor from the electric power when activated; reset capacitive energy storage means connected to activate said motor disconnecting means when charged above a predetermined trip level and being constructed to keep said motor disconnecting means activated for a time delay period without requiring any external power; and, tripping means for connecting said first capacitive energy storage means to said reset capacitive energy storage when current flow to the motor exceeds a predetermined value for a period of time, which is dependent on the magnitude of the current flow to the motor, to rapidly charge said reset capacitive energy storage means above the predetermined trip level and then to disconnect said first capacitive energy storage means from said reset capacitive energy storage means.
Claim 19
Dependent Claim
174 words
A solid state overload relay for controlling electric power to a motor comprising: current transformer means for indicating the current flow to the motor; first capacitive energy storage means connected to said current transformer for rapidly storing energy when electric power is connected to the motor; motor disconnecting means for disconnecting the motor from the electric power when activated; reset capacitive energy storage means connected to activate said motor disconnecting means when charged above a predetermined trip level and being constructed to keep said motor disconnecting means activated for a time delay period without requiring any external power; and, tripping means for connecting said first capacitive energy storage means to said reset capacitive energy storage when current flow to the motor exceeds a predetermined value for a period of time, which is dependent on the magnitude of the current flow to the motor, to rapidly charge said reset capacitive energy storage means above the predetermined trip level and then to disconnect said first capacitive energy storage means from said reset capacitive energy storage means.
Claim 20
Dependent Claim
29 words
A solid state overload relay as claimed in claim 16, including: indicating light means connecteD to light when said reset capacitive energy storage means activates said motor disconnecting 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) | 1978-03-31 | 1978-09-30 | 1979-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-31 | 1982-09-30 | 1983-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-31 | 1986-09-30 | 1987-04-01 | $7700.00 | Window Closed / Lapsed |