Electric machine protective apparatus

Abstract

A protector for motor includes a shell and an electronic circuit which consists of a sampling circuit for current detection and it is connected with an electronic identification, delay and control circuit which is connected with an operation power circuit which is in turn connected with an executive circuit. It integrates the protective functions of overloading, phase absence in high or low voltage, motor rotation blocking and short circuit into one whole for making a through protection to the motor.

Description

(1) Technical field: [0001] The invention relates to a protector, in particular to a motor protector. (two) background technology: [0002] The current motor protection devices mainly include thermal relay type and electronic type. The thermal relay type has many defects, such as being greatly affected by the ambient temperature, poor reliability, slow response, short life, and small current adaptation range. One specification only It can be equipped with motors of several power levels, and there are many contacts in the line, which increases the probability of failure. [0003] Among the electronic motor protectors, the more practical ones are the current detection type which uses the current transformer for detection and the temperature detection type which installs the temperature sensor on the motor winding. [0004] The secondary induced voltage of the current transformer used in the current detection motor protector, due to the restriction of the iron core magnetic sa...

AI Technical Summary

Problems solved by technology

[0006] In terms of the combination of the electronic protector and the motor control circuit, the normally closed contact of the relay is mostly connected in series in the control circuit of the motor. When the current is abnormal, the relay is pulled in and its normally closed contact is disconnected after being judged by the relevant circuit. The contactor loses power and trips. This method has several defects: First, the protector’s working power supply and related circuits fail, and the relay will not be able to pull in. Once the motor is abnormal, the consequences are obvious; second, the relay contacts are easy to ablate and flash over. The work is unreliable; the third is that it can only be used in the control circuit of the manual start motor and cannot be applied to the control circuit of the automatic (such as pressure, liquid level, temperature...) The application occasions are limited

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