US4246622A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overload protective device of electric motors
Assignee: Toshiba Corp
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Filing: 1978-11-01
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Granted: 1981-01-20
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Expires: 1998-11-01
Abstract
Abstract A static type overload relay is used to protect a motor against overload. The overload relay comprises an integrator for integrating the difference between the motor current and a continuous current carrying capacity of the motor. When the output of the integrator exceeds a predetermined value, a circuit breaker connected in series with the motor is tripped.
Inventors
- 👤 Kazumi Hosoda
- 👤 Masaharu Noguchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 17:43
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/08; H02H7/085
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
215 words
An overload protective device for an electric motor, comprising: a current detector for detecting current flowing through said motor and producing a detection signal proportional in magnitude to the detected current; a static overload relay including; a knee point setter for producing, when said detection signal is in excess of a predetermined level, a signal having a polarity reverse to the polarity of said detection signal and having a magnitude which increases with the magnitude of said detection signal, thereby setting a knee point at a predetermined point along an overload protective characteristic of said static overload relay, a first comparator for producing a difference in magnitude between the output of said knee point setter and said detection signal, a rated current setter for setting a value representing a predetermined continuous current carrying capacity of said motor, a second comparator for producing a difference in magnitude between the output of said rated current setter and the output of said first comparator, an integrating means for integrating an output of said second comparator, and means for producing a tripping signal when an output of said integrating means exceeds a predetermined value, and a circuit breaker connected in series with said motor for interrupting the supply of current to said motor when tripped by said tripping signal.
Claim 2
Dependent Claim
215 words
An overload protective device for an electric motor, comprising: a current detector for detecting current flowing through said motor and producing a detection signal proportional in magnitude to the detected current; a static overload relay including; a knee point setter for producing, when said detection signal is in excess of a predetermined level, a signal having a polarity reverse to the polarity of said detection signal and having a magnitude which increases with the magnitude of said detection signal, thereby setting a knee point at a predetermined point along an overload protective characteristic of said static overload relay, a first comparator for producing a difference in magnitude between the output of said knee point setter and said detection signal, a rated current setter for setting a value representing a predetermined continuous current carrying capacity of said motor, a second comparator for producing a difference in magnitude between the output of said rated current setter and the output of said first comparator, an integrating means for integrating an output of said second comparator, and means for producing a tripping signal when an output of said integrating means exceeds a predetermined value, and a circuit breaker connected in series with said motor for interrupting the supply of current to said motor when tripped by said tripping signal.
Claim 3
Dependent Claim
58 words
The overload protective device as defined in claim 1 which further comprises an instantaneous overcurrent detector connected to the output of said current detector and an OR gate circuit having inputs connected to receive the output of said instantaneous overcurrent detector and the output of said integrating means and an tripping signal connected to said output producing means.
Claim 4
Dependent Claim
243 words
An overload protective device of an electric motor, comprising: a current detector for detecting current flowing through said motor and producing a detection signal proportional in magnitude to the detected current; a static overload relay including: a knee point setter for producing, when said detection signal is in excess of a predetermined level, a signal having a polarity reverse to the polarity of said detection signal and having a magnitude which increases with the magnitude of said detection signal, thereby setting a knee point at a predetermined point along an overload protective characteristic of said static overload relay, a first comparator for producing a difference in magnitude between the output of said knee point setter and said detection signal, a rated current setter for setting a value representing a predetermined continuous current carrying capacity of said motor, a second comparator for producing a difference in magnitude between the output of said rated current setter and an output of said first comparator, an integrator for integrating an output of said second comparator, an instantaneous overcurrent detector connected to an output of said current detector, an OR gate circuit having inputs connected to receive an output of said integrator and an output of said instantaneous overcurrent detector, a transistor responsive to an output of said OR gate circuit, and a circuit breaker connected in series with said motor for interrupting the supply of current to said motor when tripped by an output of said transistor.
Claim 5
Dependent Claim
243 words
An overload protective device of an electric motor, comprising: a current detector for detecting current flowing through said motor and producing a detection signal proportional in magnitude to the detected current; a static overload relay including: a knee point setter for producing, when said detection signal is in excess of a predetermined level, a signal having a polarity reverse to the polarity of said detection signal and having a magnitude which increases with the magnitude of said detection signal, thereby setting a knee point at a predetermined point along an overload protective characteristic of said static overload relay, a first comparator for producing a difference in magnitude between the output of said knee point setter and said detection signal, a rated current setter for setting a value representing a predetermined continuous current carrying capacity of said motor, a second comparator for producing a difference in magnitude between the output of said rated current setter and an output of said first comparator, an integrator for integrating an output of said second comparator, an instantaneous overcurrent detector connected to an output of said current detector, an OR gate circuit having inputs connected to receive an output of said integrator and an output of said instantaneous overcurrent detector, a transistor responsive to an output of said OR gate circuit, and a circuit breaker connected in series with said motor for interrupting the supply of current to said motor when tripped by an output of said transistor.
References Cited (Backward Citations)
US3558978A
Cited
US3786311A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-01-20 | 1984-07-21 | 1985-01-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-20 | 1988-07-21 | 1989-01-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-20 | 1992-07-21 | 1993-01-20 | $7700.00 | Window Closed / Lapsed |