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Bearing current measuring and protecting apparatus of three-phase cage type induction motor

A technology for induction motors and bearing currents, applied in measuring devices, emergency protection devices for automatic disconnection, emergency protection circuit devices, etc. There are no related products in the test and protection device, and the current sensor or voltage sensor cannot be placed, etc., to solve the problem that the bearing current cannot be measured, the volume is small, and the work is stable and reliable.

Active Publication Date: 2009-01-07
SHANGHAI ELECTRICAL APP RES INST GRP
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AI Technical Summary

Problems solved by technology

[0004] At present, people pay more attention to the measurement and protection technology of the bearing current of large generators, but the development of the measurement and protection technology of the bearing current of the three-phase cage induction motor powered by frequency converter is lagging behind, because when the motor is working, it cannot A current sensor or voltage sensor is placed inside the bearing, so the test and protection devices for bearing current on the market are only for large generator products, but for the test of the bearing current generated by the common mode voltage caused by the power supply of the frequency converter And protective devices have not seen related products

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  • Bearing current measuring and protecting apparatus of three-phase cage type induction motor
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  • Bearing current measuring and protecting apparatus of three-phase cage type induction motor

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Embodiment Construction

[0012] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0013] The measurement of the common mode current can help to judge the flow direction of the current, that is, to determine whether the common mode current flows through the bearing and whether it flows through the rotor shaft to the load. The common-mode current measurement method is to set a high-frequency current sensor on the three-phase power line, and compare the measured common-mode current with the current on the ground wire to determine the current distribution.

[0014] If it is an ideal grounding system, all common-mode currents will be included on the ground. Therefore, by measuring the common-mode current, you can check whether the grounding system is good. If the ground wire and shield wire are all set in the current sensor for measurement, the common mode current flowing through the ideal path can be obtained. ...

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Abstract

The invention relates to a bearing current protection device of a three-phase cage induction motor, is used for measuring the bearing current of a three-phase cage induction motor which provides power for an inverter and comprises a signal collection circuit, a data processing module e and an execution protection element; wherein, a data collection circuit collects the current signals of common mode and ground wires, sends the signals to the data processing module, compares the currents of the common mode and the ground wires to determine the distribution of bearing current, test whether the grounding system is good and carry out the power-cut protection when the protection needs to be implemented. The bearing current protection device includes the main program flows of judging from (initialization) 1 to (current sampling) 2, (virtual value calculation) 3, (common-mode current calculation) 4 and to (whether faults exist); if yes, entering the (power-cut protection); if not, entering the (ending). The bearing current protection device has the beneficial effects of small volume and practicality and solves the problem that the bearing current can not be measured.

Description

technical field [0001] The invention relates to a bearing current protection device of a three-phase cage-type induction motor, which is applied to the measurement and protection of the bearing current of a three-phase cage-type induction motor powered by a frequency converter, and belongs to the technical field of motors. Background technique [0002] Energy conservation is a long-term strategic policy for international economic and social development including China, and it is also an extremely urgent task for China at present. [0003] With the development of power electronics technology, AC frequency conversion speed regulation technology has also been continuously improved and improved. This has not only caused a strong impact on the DC speed control, which has always dominated the field of speed control, but also puts forward new requirements for the traditional AC asynchronous motor. Among them, when the inverter adopts PWM control mode to supply power, the common mo...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/08H02H3/32G01R19/00
Inventor 姚鹏顾卫东吴艳红
Owner SHANGHAI ELECTRICAL APP RES INST GRP
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