| US 7,570,074 B2 | ||
| Electronic overload relay for mains-fed induction motors | ||
| Zhi Gao, Atlanta, Ga. (US); Thomas G. Habetler, Snellville, Ga. (US); Ronald G. Harley, Lawrenceville, Ga. (US); and Roy Stephen Colby, Raleigh, N.C. (US) | ||
| Assigned to Square D Company, Palatine, Ill. (US) | ||
| Filed on May 09, 2005, as Appl. No. 11/125,352. | ||
| Prior Publication US 2006/0250154 A1, Nov. 09, 2006 | ||
| Int. Cl. G01R 31/34 (2006.01); G01R 31/28 (2006.01) | ||
| U.S. Cl. 324—772 | 26 Claims |
| 20. A method of protecting an induction motor during running overloads, said motor having a rotor and a stator, said method
comprising
connecting the motor to an overload protection relay that can be tripped to interrupt power to the motor in the event of an
overload,
tracking the stator winding temperature of the motor during running overloads with a hybrid thermal model by online adjustment
in the said hybrid thermal model, and
tripping the overload protection relay in response to a predetermined thermal condition represented by the stator winding
temperature tracked with said hybrid thermal model.
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