US4796142A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overload protection apparatus for emulating the response of a thermal overload
Assignee: Schneider Electric USA Inc
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Filing: 1986-10-16
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Granted: 1989-01-03
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Expires: 2006-10-16
Abstract
Abstract A thermal overload detector and interrupter has a current transformer for monitoring load current and providing a current value signal, a microprocessor for calculating values related to load current and the thermal characteristics of a load, and an interrupter for selectively conducting and interrupting load current. The microprocessor computes a square current value from the current value signal and multiplies the square current value by a predetermined constant to obtain a multiplied square current value. The predetermined constant is related to the heat transfer characteristics of the load. A present running sum is computed in the microprocessor by adding the multiplied square current value to a past test value. The microprocessor then computes a proportionate present running sum by multiplying the present running sum by the predetermined constant. A present test value is computed by subtracting the proportionate present running sum from the present running sum. If the present test value exceeds a trip value, the microprocessor causes the interrupter to trip and interrupt the load current.
Inventors
- 👤 James T. Libert
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 15:47
CPC Classifications
H; H02; H02H; H02H6/00; H02H6/005; H02H7/00; H02H7/08; H02H7/0833
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
216 words
A thermal overload detector and current interrupter for a device supplying load current to a load which may store heat and can become subject to thermal overload comprising: load current measuring means for providing a current value signal proportionate to the load current; processor means operatively connected to said load current measuring means, said processor means for computing the square of the current value signal to obtain a square current value, for computing a multiplied square current value by multiplying said square current value by a predetermined constant related to the heat transfer characteristics of the load, for computing a present running sum by adding the multiplied square current value to a past test value, for computing a proportionate present running sum by multiplying the present running sum by the predetermined constant, for computing a present test value related to stored heat in the load by subtracting the proportionate present running sum from the present running sum, for determining whether the present test value exceeds a trip value which is related to the thermal overload of the load, and for issuing a turn off signal if the present test value exceeds the trip value; and interrupting means for responding to the turn off signal to interrupt the load current when the turn off signal is present.
Claim 2
Dependent Claim
216 words
A thermal overload detector and current interrupter for a device supplying load current to a load which may store heat and can become subject to thermal overload comprising: load current measuring means for providing a current value signal proportionate to the load current; processor means operatively connected to said load current measuring means, said processor means for computing the square of the current value signal to obtain a square current value, for computing a multiplied square current value by multiplying said square current value by a predetermined constant related to the heat transfer characteristics of the load, for computing a present running sum by adding the multiplied square current value to a past test value, for computing a proportionate present running sum by multiplying the present running sum by the predetermined constant, for computing a present test value related to stored heat in the load by subtracting the proportionate present running sum from the present running sum, for determining whether the present test value exceeds a trip value which is related to the thermal overload of the load, and for issuing a turn off signal if the present test value exceeds the trip value; and interrupting means for responding to the turn off signal to interrupt the load current when the turn off signal is present.
Claim 3
Dependent Claim
49 words
The thermal overload detector and current interrupter of claim 1 wherein said load current measuring means comprises: at least one current transformer providing an analog current value signal proportionate to the load current; and converter means for converting the analog current value signal to a digital current value signal.
Claim 4
Dependent Claim
28 words
The thermal overload detector and current interrupter of claim 2 wherein said processor means and said converter means is a microprocessor having at least one analog input port.
Claim 5
Dependent Claim
52 words
The thermal detector and current interrupter of claim 1 wherein: said interrupter means comprises; a plurality of thryristors selectively conducting load current in response to a firing signal; and a firing means for selectively generating firing signals in the absence of a turn off signal; and said processor means is a microprocessor.
Claim 6
Independent Claim
240 words
A method for detecting and interrupting an electric current overload with an apparatus including a load current measuring means for providing a current value signal proportionate to load current, a microprocessor receiving the current value signal, and an interrupter for selectively conducting and interrupting the load current operatively connected to said microprocessor, said method comprising the steps of: providing the current value signal with said load current measuring means; receiving the current value signal with said microprocessor; computing a value of the square of the current value to obtain a square current value with said microprocessor; computing a multiplied square current value by multiplying the square current value by a predetermined constant related to the heat transfer characteristics of the load with said microprocessor; computing a present running sum by adding the multiplied square current value to a past test value with said microprocessor; computing a proportionate present running sum by multiplying the present running sum by the predetermined constant with said microprocessor; computing a present test value related to stored heat in the load by subtracting the proportionate present running sum from the present sum with said microprocessor; determining whether the present test value exceeds a trip value which is related to the thermal overload of the load with said microprocessor; issuing a trip signal when the present test value exceeds a trip value with said microprocessor; interrupting load current with said interrupter when the trip signal is present.
Claim 7
Independent Claim
240 words
A method for detecting and interrupting an electric current overload with an apparatus including a load current measuring means for providing a current value signal proportionate to load current, a microprocessor receiving the current value signal, and an interrupter for selectively conducting and interrupting the load current operatively connected to said microprocessor, said method comprising the steps of: providing the current value signal with said load current measuring means; receiving the current value signal with said microprocessor; computing a value of the square of the current value to obtain a square current value with said microprocessor; computing a multiplied square current value by multiplying the square current value by a predetermined constant related to the heat transfer characteristics of the load with said microprocessor; computing a present running sum by adding the multiplied square current value to a past test value with said microprocessor; computing a proportionate present running sum by multiplying the present running sum by the predetermined constant with said microprocessor; computing a present test value related to stored heat in the load by subtracting the proportionate present running sum from the present sum with said microprocessor; determining whether the present test value exceeds a trip value which is related to the thermal overload of the load with said microprocessor; issuing a trip signal when the present test value exceeds a trip value with said microprocessor; interrupting load current with said interrupter when the trip signal is present.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-01-03 | 1992-07-04 | 1993-01-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-01-03 | 1996-07-04 | 1997-01-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-01-03 | 2000-07-04 | 2001-01-03 | $7700.00 | Window Closed / Lapsed |