Thermal relays, contactors, circuit working principle and the role of

Contactors and thermal relays are working and the motor starter circuit protection devices, their role is faulty motor or the load exceeds the rated load, the motor current exceeds the rated current, the thermal relay mcb circuit breaker, normally closed contact normally open , cut off the power supply to the motor contactor coil circuit, electric meter open, cutting off power to the motor, the protection of the motor, to avoid damage to the thermal relay is using Joule heat, any energized electric transformer Joule heat, the use of this principle, the control switch the closed off. Contactor is using thermal principle, can puncture the air and high-voltage electrical conductivity.