Often positive, reverse and frequent start of the motor, suitable for thermal relay to protect. right?
The thermal relay is used in the motor protection circuit.
Thermal relay is mainly used to protect the motor overload, so the choice must understand the situation of the motor, such as the working environment, starting current, load nature, working system, allowing overload capacity.
1, in principle, the safety characteristics of the thermal relay should be as close as possible or even close to the overload characteristics of the motor, or under the overload characteristics of the motor, while the motor overload and start the moment, the thermal relay should not be affected (not action).
2, when the thermal relay for the protection of long-term work or intermittent long-term work of the motor, the general motor rated current to use. For example, the setting value of the thermal relay can be equal to 0.95 to 1.05 times the rated current of the motor, or the value of the heat relay setting current is equal to the rated current of the motor and then adjusted.
3, when the thermal relay for the protection of repeated short-term working system of the motor, the thermal relay only a certain range of adaptability. If a lot of times a short time operation, we must use the speed of the current transformer thermal current transformer.
4, for positive and negative reversing and frequent work of the special motor, should not use thermal relay as overload protection device, but should be buried in the motor winding temperature relay or thermistor to protect.
For frequent frequent contact with the thermal relay is not too large, with the voltage size of the relationship, or contactor frequent suction and if the contactor quality is not easy to stick thermal relay will work
For the special work reversing and breaking off the special work of the motor, should not use thermal relay as overload protection device, but should use the buried motor winding temperature relay or thermistor to protect.
According to GB755, the working system of the motor can be divided into 10 kinds from the S1 - S10, so the factory with the motor, according to the equipment work system will be suitable for the kind of work under the system of the motor. If you are buying a separate motor, and manufacturers to declare the motor running in order to select the appropriate motor.
This is not related to thermal relay protection. According to the different working system, pay attention to the choice of AC contactor to prevent contactor heat adhesion.
