General knowledge of motor protection

1.Electric motors burn down more easily than in the past

Due to the continuous development of insulation technology, the design of the motor requires both increasing output and decreasing volume, so that the heat capacity of the new motor is smaller and smaller, and the overload capacity is weaker and weaker.Moreover, due to the improvement of production automation, the motor is required to operate in frequent starting, braking, positive and negative rotation, variable load and other ways, which puts forward higher requirements for the motor protection device.In addition, the motor is more widely used, often work in the environment is very bad occasions, such as wet, high temperature, dust, corrosion and other occasions.All of these, resulting in motor more vulnerable to damage, especially overload, short circuit, lack of phase, cleaning and other faults occur at the highest frequency.

2. The protection effect of traditional protection device is not ideal

The traditional motor protection device is mainly thermal relay, but thermal relay has low sensitivity, large error, poor stability and unreliable protection.The fact is also such, although many equipment installed thermal relays, but motor damage and affect the normal production phenomenon is still widespread.

3. Development status of motor protection

Motor protector has by the mechanical development for electronic and intelligent, can directly show the motor parameters such as current, voltage, temperature, high sensitivity, high reliability, versatility, convenient debugging, after the fault types of protection operation be clear at a glance, both to reduce the damage of the motor, and has greatly helped the fault judgment, to resume production troubleshooting and shorten the time of manufacturing.In addition, the motor eccentricity detection technology using the motor air gap magnetic field makes it possible to monitor the motor wear status online. By showing the variation trend of the motor eccentricity degree through the curve, the bearing wear and the faults such as inner and outer circling can be found early, so as to achieve early detection and treatment and avoid the occurrence of ribcage cleaning accidents.

4.Principle of protector selection

Reasonable selection of motor protection device can not only give full play to the overload capacity of motor, but also avoid damage, so as to improve the reliability of power drive system and continuity of production.The specific function selection should comprehensively consider the value of the motor itself, the type of load, the use environment, the importance of the main equipment of the motor, whether the withdrawal of the motor from operation will seriously affect the production system and other factors, and strive to achieve economic and reasonable.

5. Ideal motor protector

The ideal motor protector is not the most functional, nor the so-called most advanced, but should meet the actual needs of the site, achieve the unification of economy and reliability, with a higher performance price.According to the actual situation of the site to choose a reasonable type of protector, function, while considering the protector installation, adjustment, easy to use, more importantly, to choose a high-quality protector.