Patent US3582982A successfully refreshed from Google Patents.
US3582982A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic motor overload relay control system
Assignee: Cutler Hammer Inc
•
Filing: 1969-08-26
•
Granted: 1971-06-01
•
Expires: 1989-08-26
Abstract
Abstract A solid-state differential amplifier system that trips out a relay when an overload condition occurs in a motor power supply circuit. An overload current sensing circuit provides a voltage proportional to the peak value of one or more overload conditions and includes a current avalanche device for protecting the following devices from excessive voltages. This voltage operates a timing circuit to provide a control voltage having an inverse time delay relative to the magnitude of the overload condition sensed. The control voltage upon reaching an ultimate trip value that is adjustable trips a differential amplifier to deenergize the overload relay. A diode-resistor circuit makes the tripping action regenerative once it is started for positive dropout of the overload relay. A constant current circuit supplies operating current to the differential amplifier. A voltage divider provides a voltage that normally biases the differential amplifier on to energize the overload relay and includes a potentiometer for adjusting the ultimate trip current value. The voltage divider supplies an operating voltage for the constant current circuit. An optional instantaneous trip circuit receives a reference voltage from the voltage divider circuit and functions to cause immediate tripping of the differential amplifier when the overload current exceeds a predetermined point above the ultimate trip value. The system provides time delayed automatic or manual reset as alternatives with minor modification.
Inventors
- 👤 Merle R Swinehart
- 👤 Richard A Greiner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 18:29
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/093; H02H3/02; H02H3/06
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
193 words
In an electronic overload relay control system for monitoring the current in one or more power lines supplying a load device, the combination comprising: an overload current sensing circuit for sensing the current in one or more power lines and for providing a signal proportional thereto; an inverse time-overcurrent circuit responsive to said signal for providing a time delayed trip voltage; a differential amplifier including a circuit for supplying constant current for operation thereof; a power supply source for supplying unidirectional supply voltage to said differential amplifier and said constant current circuit; a voltage divider supplied from said source for applying an input control signal to said constant current circuit and an operating control signal to said differential amplifier to render it operative; an overload relay responsive to said operative condition of said differential amplifier for energizing said relay and operating its contacts to complete the power line connection; and said differential amplifier being responsive to said time delayed trip signal exceeding a predetermined ultimate trip value indicative of a sustained overload condition for tripping said relay into its restored condition, causing it to restore its contacts and interrupt the power line connection.
Claim 2
Dependent Claim
193 words
In an electronic overload relay control system for monitoring the current in one or more power lines supplying a load device, the combination comprising: an overload current sensing circuit for sensing the current in one or more power lines and for providing a signal proportional thereto; an inverse time-overcurrent circuit responsive to said signal for providing a time delayed trip voltage; a differential amplifier including a circuit for supplying constant current for operation thereof; a power supply source for supplying unidirectional supply voltage to said differential amplifier and said constant current circuit; a voltage divider supplied from said source for applying an input control signal to said constant current circuit and an operating control signal to said differential amplifier to render it operative; an overload relay responsive to said operative condition of said differential amplifier for energizing said relay and operating its contacts to complete the power line connection; and said differential amplifier being responsive to said time delayed trip signal exceeding a predetermined ultimate trip value indicative of a sustained overload condition for tripping said relay into its restored condition, causing it to restore its contacts and interrupt the power line connection.
Claim 3
Dependent Claim
65 words
The invention defined in claim 1, wherein said differential amplifier comprises: a pair of field effect transistors one of which is controlled by saId operating control signal coming from said voltage divider to cause energization of said overload relay and the other of which is controlled by said time delayed trip signal when it exceeds said predetermined value to cause deenergization of said overload relay.
Claim 4
Dependent Claim
57 words
The invention defined in claim 2, wherein said differential amplifier also comprises: a pair of bipolar transistors one of which is controlled by said one field effect transistor and the other of which is controlled by said other field effect transistor; and a third bipolar transistor controlled by said one bipolar transistor for energizing said overload relay.
Claim 5
Dependent Claim
60 words
The invention defined in claim 3, wherein said differential amplifier also comprises: a lockout circuit operable when said third bipolar transistor starts to turn off for shifting the supply voltage on said one field effect transistor in a direction causing further turn-off of said one bipolar transistor thereby producing a regenerative action that causes positive deenergization of said overload relay.
Claim 6
Dependent Claim
76 words
The invention defined in claim 4 wherein said lockout circuit comprises: a unidirectional diode and a resistor connected in series from the output of said third bipolar transistor to the source electrode of said one field effect transistor; and said differential amplifier further comprising a source resistor connecting said source electrode to said constant current circuit whereby current flow through said lockout circuit increases the voltage drop on said source resistor to cause said regenerative action.
Claim 7
Dependent Claim
41 words
The invention defined in claim 5, together with: a normally closed manual reset switch connected across the resistor of said lockout circuit operable when closed to prevent resetting and operable when opened to cause resetting with reenergization of said overload relay.
Claim 8
Dependent Claim
97 words
The invention defined in claim 1, wherein aid overload current sensing circuit comprises: a current transformer for each power line that is being monitored; each said current transformer having a toroidal secondary winding through which the associated power line passes; a resistor across each said secondary winding for providing a voltage proportional to the current in the associated power line; a storage capacitor; and a circuit comprising a rectifier for each secondary winding connecting all the secondary windings to said capacitor to provide thereon a direct voltage proportional to the highest peak current on the power lines.
Claim 9
Dependent Claim
40 words
The invention defined in claim 7, wherein said overload current sensing circuit also comprises; a solid-state device in the return path from said storage capacitor back to said secondary windings to compensate for the voltage offset caused by said rectifiers.
Claim 10
Dependent Claim
78 words
The invention defined in claim 7, wherein said overload current sensing circuit also comprises: a unidirectional conducting device for compensating for the voltage offset caused by said rectifiers; a resistive circuit connected to said power supply source for causing current flow through said unidirectional conducting device in its forward low impedance direction; and means connecting said unidirectional conducting device in its reverse high impedance direction in the return path from said storage capacitor back to said secondary windings.
Claim 11
Dependent Claim
47 words
The invention defined in claim 8, wherein said overload current sensing circuit further comprises: a thermistor connected across said unidirectional conducting device to compensate for the difference in thermal coefficients between said rectifiers which are silicon devices and said unidirectional conducting device which is a germanium device.
Claim 12
Dependent Claim
56 words
The invention defined in claim 1, together with: instantaneous trip means responsive when said signal provided by said overload current sensing means exceeds a given value higher than said predetermined value for producing an instantaneous increase in said trip signal to said differential amplifier thereby tO cause tripping of said overload relay without any time delay.
Claim 13
Dependent Claim
153 words
The invention defined in claim 1, wherein said overload current sensing circuit comprises: a current transformer having a secondary winding coupled to each power line that is being monitored; a storage capacitor; means comprising a rectifier for each said secondary winding for charging said storage capacitor to a direct voltage proportional to the highest peak current of any of the power lines, said direct voltage being applied to said inverse time-overcurrent circuit; together with an instantaneous trip circuit comprising; a transistor; means for applying a reference voltage from said voltage divider to said transistor to maintain it nonconductive; means responsive to the voltage on said storage capacitor exceeding a value proportional to said reference voltage for rendering said transistor conducting; and means responsive to conduction of said transistor for causing an instantaneous increase in the trip signal to said differential amplifier thereby to cause tripout of said overload relay without any time delay.
Claim 14
Dependent Claim
55 words
The invention defined in claim 12, wherein said means responsive to the voltage on said storage capacitor exceeding a value proportional to said reference voltage for rendering said transistor conductive comprises: a potentiometer connected across said storage capacitor for selecting a portion of the voltage thereof for application to said transistor for instantaneous trip purposes.
Claim 15
Dependent Claim
75 words
The invention defined in claim 12, wherein said voltage divider comprises: a Zener diode for providing a constant voltage for three purposes, one of which is to apply a constant input signal to said constant current circuit, another of which is to maintain the operating control signal that goes to the differential amplifier constant, and the third of which is to maintain constant the reference voltage going to the transistor of the instantaneous trip circuit.
Claim 16
Dependent Claim
40 words
The invention defined in claim 1, wherein said inverse time-overcurrent circuit and said differential amplifier comprise: automatic time delay resetting means operable following termination of the overload condition for causing reenergization of said overload relay after a predetermined time delay.
Claim 17
Dependent Claim
37 words
The invention defined in claim 1, wherein said voltage divider comprises: means for adjusting the value of the operating control signal applied to said differential amplifier thereby to adjust the ultimate trip valve of the overload current.
Claim 18
Dependent Claim
58 words
The invention defined in claim 1, wherein said load is a motor and said inverse time-overcurrent circuit comprises: an RC circuit that responds to said overload current sensing circuit signal for providing an inverse current-time function; and including means operable when said signal reaches a high value for modifying said inverse current-time function to match the motor characteristics.
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) | 1974-05-31 | 1974-11-30 | 1975-06-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-31 | 1978-11-30 | 1979-06-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-31 | 1982-11-30 | 1983-06-01 | $7700.00 | Window Closed / Lapsed |