Electronic overload relay for mains-fed induction motors

A technology of rotor resistance and induction motor, which is applied in the direction of motor generator test, emergency protection circuit device, control system, etc., to achieve the effect of reducing unnecessary downtime

Active Publication Date: 2013-03-27
SQUARE D CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It is often assumed that a constant 10°C higher winding temperature than the temperature limit cuts the motor life in half

Method used

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  • Electronic overload relay for mains-fed induction motors
  • Electronic overload relay for mains-fed induction motors
  • Electronic overload relay for mains-fed induction motors

Examples

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Embodiment Construction

[0037] Turning now to the drawings, Figure 1 shows the overall configuration of a system for estimating stator winding temperature in an induction machine. This estimated temperature can then be used to control the tripping of electronic relays that protect the motor from overload conditions. The system includes an inductance estimator 10 , a rotor resistance estimator 12 , a rotor temperature estimator 14 , and a stator temperature estimator 16 . The on-line signals supplied to the system include signals i representing samples of the motor terminal current and voltage, respectively s and v s , the signal R representing the resistance of the stator in the motor s , and a signal representing NEMA Design A, B, C, or D of the motor. The output of the system is a signal representing the estimated stator temperature θ s HTM .

[0038] The four estimators 10 to 16 are preferably realized by a single microprocessor programmed to execute the algorithm for computing the desired e...

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Abstract

An induction motor having a rotor and a stator is protected during running overloads by 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 hybrid thermal model, and tripping the overload protection relay in response to a predetermined running overload condition represented by the tracked stator winding temperature. In one embodiment of the invention, the stator winding temperature is tracked by use of an online hybrid thermal model that uses the resistance of the rotor as an indicator of rotor temperature and thus of the thermal operating conditions of the motor. The hybrid thermal model incorporates rotor losses and heat transfer between the rotor and the stator, and approximates the thermal characteristics of the rotor and stator.

Description

technical field [0001] This invention relates generally to electronic overload relays for mains-fed induction motors. More specifically, the present invention relates to a system for controlling electronic overload relays for mains-fed induction motors. Background technique [0002] The permissible temperature limits for the motor windings are mainly determined by the insulation of the motor. Applicable standards (UL, CSA, IEC, and NEMA) distinguish between different insulation classes and corresponding temperature limits. Typical allowable temperatures inside the stator windings are in the Information Guide for General Purpose Industrial AC Small and Medium Squirrel-Cage Induction Motor Standards (Information Guide for General Purpose Industrial AC Small and Medium Squirrel-Cage Induction Motor Standards), NEMA Standard MG1- 2003, given in August 2003. [0003] If the motor is continuously operated at an excessively high temperature, the aging process is accelerated. T...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H6/00G01R31/34
CPCH02H7/085G01R31/343H02H6/005H02P29/64H02P23/14
Inventor 高智托马斯·G.·哈伯特勒罗纳尔德·G.·哈雷罗伊·史蒂芬·科尔比
Owner SQUARE D CO
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