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Thermal relays and motor protectors cannot be compared

Article Source:Thermal protectorAuthor:YaxunPopularity:Published time:2019-10-17 11:07

It is a well-known fact that bimetal thermal relays and motor protectors cannot be equated. According to incomplete statistics when, occur about every 100 motor burned, thermal relay can work less than 30 times. The reason is multi-faceted, the main reason is that thermal relays have insurmountable defects. For example, a bimetal is prone to thermal fatigue, and it is difficult to recover from the initial after several times of overheating. Therefore, many electromechanical devices do not use thermal relays at the beginning of the design.

Motor protectors have been in the world for more than 30 years, and still can't stop the burning of electric motors. The reasons are mainly the following three aspects:
1. There is no correct product function positioning during design, which are essential functions? What are the auxiliary? (Not as many features as possible)
2. There is no ideal current sensor at the moment, and the motor protector produced cannot meet the following requirements:
Block the occurrence of misoperations;
Good interchangeability with thermal relays;
It is watered and solidified to suit various harsh environments and prolong its service life.
3, failed to bring immediate benefits to the user.

More than 97% of low-voltage motors are destroyed due to overcurrent, resulting in overcurrent (locked rotor), start-up timeout, phase loss, overvoltage, undervoltage, and poor three-phase line contact. The overcurrent caused by overload (blocking), starting timeout, overvoltage, undervoltage, etc. is a three-phase current equalization increase; The overcurrent caused by phase loss, poor contact, voltage imbalance, etc. is one of the phase or two phase current increases. Therefore, high precision and sinusoidal current sampling are the key to motor protectors.

The destruction of an electric motor is not only costly but also repaired:
Sometimes it takes time for the mechanic to take time to dismantle the damaged motor from the mechanical device, which is time consuming and delays production; Once the factory is critical to the destruction of the motor, the indirect damage will be even greater. Increased expenses and increased processing costs of the product. The repaired motor is not as good as the original, which accelerates the depreciation of the whole machine. Today, when copper prices are so high, it is especially important to protect and maintain the motor from burning.

A small motor with hundreds of thousands of tens of thousands of dollars is not commensurate with a thermal relay that is not very reliable. The power consumption is not counted (20 is equivalent to about 60W, 60 is equivalent to about 80W, and 150 is equivalent to about 100W), and it does not provide the most intimate protection for the motor. In the past, when energy and resources were abundant, energy conservation and resource conservation were not taken seriously by society. Today's situation is so different when the government is so concerned. Therefore, the birth of an ideal motor protector is an inevitable choice in today's society.
motor protectors