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Default phase protecting method and device for three-phase motor

A three-phase motor, phase loss protection technology, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve the problems of not being able to protect in time, and achieve the effect of real-time monitoring of current

Inactive Publication Date: 2012-01-18
宁波沃弗圣龙环境技术有限公司
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Problems solved by technology

Since the actual load of industrial motors is often only 60% to 70% of the rated power, in this case, the lack of phase, the operating current of the lack of phase will often not exceed the setting value of the thermal relay, resulting in failure to protect in time

Method used

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  • Default phase protecting method and device for three-phase motor
  • Default phase protecting method and device for three-phase motor
  • Default phase protecting method and device for three-phase motor

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Embodiment Construction

[0022] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

[0023] Depend on figure 1 As can be seen from the star-delta connection diagram of the three-phase motor with the weak current control loop in the present invention, it includes the weak current control part in the dotted line frame, Ic, I1 are line current and phase current sampling respectively, and PLC collects the current Ic, I1 For calculation and analysis, KA1 is the relay output.

[0024] 1. Three-phase motor phase loss start protection

[0025] When the three-phase motor starts normally, the starting current at the moment of starting is the starting current (generally 3 to 7 times the rated current, and 1 / 3 of the direct starting when the star connection method is used for step-down starting). As the motor starts to rotate, Winding current drops rapidly to normal operating current.

[0026] When the three-phase motor starts...

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Abstract

The invention discloses a default phase protecting method for a three-phase motor. The default phase protecting method comprises the following steps of: providing a weak current control loop on the basis of a main loop and a controller control loop of the three-phase motor; collecting line current and phase current of the three-phase motor by a current sampling device in the weak current control loop so as to obtain values of one group of line current Ic and phase current I1, line current Ib and phase current I3, or line current Ia and phase current I2; transmitting the values to a microcomputer which is connected with the current sampling device; and sending an instruction to control the ON / OFF of a relay KA1 by the microcomputer through calculation and analysis so as to realize the default phase protection of the three-phase motor. The default phase protecting method cannot be affected by the magnitude of current, has the characteristic of high response speed, and can be used for realizing the star-connection default-phase start protection and delta-connection default-phase operation protection of the three-phase motor.

Description

technical field [0001] The invention relates to a motor protection scheme, in particular to a phase loss protection method and device for a three-phase motor. Background technique [0002] Three-phase motor phase failure is one of the common causes of three-phase motor burnout. At present, thermal overload relays are generally used for protection. This kind of protection uses the principle that the bimetal strip deforms and trips when it generates heat. The tripping time has a great relationship with the current. Since the actual load of industrial motors is often only 60% to 70% of the rated power, in this case the lack of phase, the lack of phase operating current will often not exceed the setting value of the thermal relay, resulting in timely protection. Contents of the invention [0003] The technical problem to be solved by the present invention is to provide a phase loss protection method and device for a three-phase motor that is not affected by the magnitude of t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/09
Inventor 朱甬王丰华曹丹辉
Owner 宁波沃弗圣龙环境技术有限公司
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