US4789834A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for testing of induction motor overload protection device
Assignee: General Electric Co
•
Filing: 1986-12-22
•
Granted: 1988-12-06
•
Expires: 2006-12-22
Abstract
Abstract A method and apparatus for testing the operability of an overload protection device for an induction motor, rapidly and without the need to mechanically load the motor output shaft. A rectifier circuit converts a standard AC input power signal to an unfiltered full wave rectified output power signal which is applied to the input terminals of the motor under test to rapidly heat the overload device to its trip temperature. The output power signal is periodically interrupted for brief periods of sufficient duration to extinguish any arcing occasioned by the opening of the overload device contacts. The period between successive interrupt periods is selected to be short enough to extinguish any such arcing before the contacts are damaged. If the contacts of the protection device fail to open within a predetermined time period, a signal is generated to indicate that the overload device has failed to operate properly.
Inventors
- 👤 Lawrence J. Koopman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:49
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/34; G01R31/343
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
198 words
A method of testing the operability of an overload protection device incorporated in a power circuit for an AC induction motor having motor power terminals and motor windings adapted for energization by a power signal applied across the power terminals, which device is of the type having contacts in the motor power circuit operative to open thereby de-energizing the motor windings when the device temperature exceeds a predetermined temperature limit, said method comprising the steps of: applying an unfiltered full wave rectified AC power signal across the motor power terminals to rapidly raise the temperature of the device above the temperature limit; periodically decoupling the power signal from the motor terminals for a relatively brief interrupt period of sufficient duration to extinguish any arcing occasioned by the opening of the contacts of the overload device, the period between successive interrupt periods being short enough to prevent arc damage to the contacts; monitoring the motor circuit to detect opening of the overload device contacts; measuring the time from application of power to the motor terminals; and generating a signal indicating that the overload device has failed the test if the contacts fails to open within a predetermined time interval.
Claim 2
Independent Claim
198 words
A method of testing the operability of an overload protection device incorporated in a power circuit for an AC induction motor having motor power terminals and motor windings adapted for energization by a power signal applied across the power terminals, which device is of the type having contacts in the motor power circuit operative to open thereby de-energizing the motor windings when the device temperature exceeds a predetermined temperature limit, said method comprising the steps of: applying an unfiltered full wave rectified AC power signal across the motor power terminals to rapidly raise the temperature of the device above the temperature limit; periodically decoupling the power signal from the motor terminals for a relatively brief interrupt period of sufficient duration to extinguish any arcing occasioned by the opening of the contacts of the overload device, the period between successive interrupt periods being short enough to prevent arc damage to the contacts; monitoring the motor circuit to detect opening of the overload device contacts; measuring the time from application of power to the motor terminals; and generating a signal indicating that the overload device has failed the test if the contacts fails to open within a predetermined time interval.
Claim 3
Dependent Claim
33 words
The method of claim 1 wherein the duration of each interrupt period is not substantially less than 4 milliseconds and the period between successive interrupt periods is not substantially greeater than 60 milliseconds.
Claim 4
Dependent Claim
17 words
The method of claim 2 wherein the predetermined time interval is not substantially greater than 8 seconds.
Claim 5
Dependent Claim
28 words
The method of claim 1 wherein the step of monitoring the motor circuit comprises monitoring the current flow in the motor circuit to detect when the contacts open.
Claim 6
Dependent Claim
204 words
Apparatus for testing the operability of an overload protection device incorporated in an AC induction motor having motor input terminals and motor windings adapted for energization by a power signal applied to the input terminals, which device has contacts operative to disconnect the motor windings from the motor input terminals when the device temperature exceeds a predetermined temperature limit, said apparatus comprising: means for converting an AC input power signal to an unfiltered full wave rectified output power signal and applying said output power signal to the input terminals of the motor under test to rapidly raise the overload device temperature above the predetermined temperature limit; timing means for periodically interrupting said output power signal for relatively brief interrupt periods of sufficient duration to extinguish such arcing as may be occasioned by the opening of the overload device contacts, the period between successive interrupt periods being short enough to extinguish such arcing before the contacts are damaged; means for detecting the opening of the overload device contacts; means for determining if the contacts open within a predetermined time period; and means for generating a signal if the contacts fail to open within said predetermined period indicating that the overload device failed to operate properly.
Claim 7
Dependent Claim
204 words
Apparatus for testing the operability of an overload protection device incorporated in an AC induction motor having motor input terminals and motor windings adapted for energization by a power signal applied to the input terminals, which device has contacts operative to disconnect the motor windings from the motor input terminals when the device temperature exceeds a predetermined temperature limit, said apparatus comprising: means for converting an AC input power signal to an unfiltered full wave rectified output power signal and applying said output power signal to the input terminals of the motor under test to rapidly raise the overload device temperature above the predetermined temperature limit; timing means for periodically interrupting said output power signal for relatively brief interrupt periods of sufficient duration to extinguish such arcing as may be occasioned by the opening of the overload device contacts, the period between successive interrupt periods being short enough to extinguish such arcing before the contacts are damaged; means for detecting the opening of the overload device contacts; means for determining if the contacts open within a predetermined time period; and means for generating a signal if the contacts fail to open within said predetermined period indicating that the overload device failed to operate properly.
Claim 8
Dependent Claim
16 words
The apparatus of claim 5 wherein said interrupt periods are not substantially shorter than 4 milliseconds.
Claim 9
Dependent Claim
18 words
The apparatus of claim 6 wherein the time between interrupt periods is not substantially greater than 60 milliseconds.
Claim 10
Dependent Claim
14 words
The apparatus of claim 7 wherein said predetermined period is less than 8 seconds.
References Cited (Backward Citations)
US2541121A
Cited
US3924160A
Cited
US4258325A
Cited
US4340853A
Cited
US4463571A
Cited
US4692939A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-12-06 | 1992-06-06 | 1992-12-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-06 | 1996-06-06 | 1996-12-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-06 | 2000-06-06 | 2000-12-06 | $7700.00 | Window Closed / Lapsed |