Elements with protective functions must be connected in series, with an appropriate supply, and by thermal dissipation, which occurs due to the passage of the current through the internal resistance, a deformation of the disk occurs, causing the contacts to open and the power supply the motor stops automatically. After a relatively lower temperature is reached than the specified temperature, the protector must be switched back on. Due to this reclosing, two types of protectors can occur: the protector with automatic reclosing and with manual reclosing. The protectors can also be used in three-phase motors, but only in Y-connected motors leeson 120067.00. The advantage is the combination of the current and temperature sensitive protector and the possibility of automatic reclosing.
The disadvantage is that the current limiting, the protector being connected directly to the coil of the single-phase motor and the application directed to three-phase motors only in the center of the Y-connection. Thus, the protectors consist of bimetallic components with closed contacts, mainly used in motors induction, to protect against overheating generated by overloads, allowing rotor locking and voltage drops.