A power supply network shall contain a device which protects against a short circuit, Gates BX35 such as a fuse or circuit breaker, a disconnecting device for maintenance, a disconnector or a knife or circuit breaker, a device which defines the operational state of the motor, which is a circuit breaker or magnetic switch and an overload protection device, which is the thermal relay.
The thermal relay operates only when the device for switching on and off the engine is a magnetic switch and the switches allow manual local or manual remote control and automatic engine control. Usually we use pushbuttons or spring wrenches to energize and deenergize the magnetic wrench coil. When using pushbuttons for the operation of magnetic switches (contactors), the operator is not subject to electrical shock hazards because the button is in the control circuit, where the voltage is lower after the control transformer. Starting from the principle of closing the coils of the electric motor to the corresponding voltage level, we must start the drive. The drive defines the operating state and the operating conditions of the motor.