If the operating temperature of the bimetallic is relatively low, this element will return instantly to its initial mode, enabling the closure of the contacts. The thermostats can be turned to alarm systems, shutdown or both of three-phase electric motors. In general, the machines are installed on separate coil heads and connected in series with the contactor coil, which can be varied according to the degree of safety and customer specification, three thermostats can be leeson ac motors used, one per phase , or six thermostats, in groups of two per phase.
Therefore, bimetallic thermal protectors consist of sensors with thermal properties that have normally closed silver contacts, fully capable of opening upon reaching a temperature which is normally high. In the event of an alarm and shutdown, with two thermostats per phase, the alarm thermostats shall be appropriate for this purpose in raising the engine’s intended temperature, at the same time that the shutdown thermostats will act on the maximum temperature of the insulation material. Thermostats are also used in specific applications of single-phase machines. In specific cases, the thermostat must be operated in series with the motor supply.