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Motor protector types
Mar 16, 2017

(A) the thermal relay is the introduction of technology development of the Soviet Union in the early 50 's metal plate for mechanical motor overload protection. It is in the area of motor overload protection with inverse time performance and characteristics of simple structure. But there are few functions, no phase-failure protection, poor ventilation of motor, sweep the Chamber, locked rotor, long-term overload; frequently start fault does not afford protection. This is mainly because the heat relay curves and physical protection of the motor curve is inconsistent, losing protection. And repeat the poor performance, and cannot be used again after the current overload or short circuit, adjusting errors large and vulnerable to the influence of environment temperature malfunction or rejection, backward, supplies much more power, performance indicators and other defects.

(B) the thermal relay is a double disc made of sheet metal or other types of relays, has simple structure, reliable protection range widely, but slow, returned long, more than 3KW Delta connection of motor should not be used. Now widely used in electric fans, refrigerators and air conditioning compressors and so on.

Relay different from the thermal relay. Temperature relay is installed inside the motor, temperature changes during the action. Thermal relays installed on power lines, by current heating action.