17AM-D series thermal protector is a current sensitive and temperature automatic response device. It is connected in series to the winding of motor. The protector changes with the temperature of winding and current of a motor. When the heat generated by the increasing temperature and current from the protected appliances transmits to double-metal element, and reaching the temperature value of scheduled movement, the double-metal element will move immediately so that the contact will be switched off and the circuit will be cut off. When the temperature of motor winding decreases to the rated temperature value of reposition, bimetal element will return to its initial state, the moving contact will be closed and the circuit will be on.
17AM-D+PTC is the 17AM-D series thermal protector pulsing PTC element which can generate heat and connect with contact in parallel. When 17AM-D protector in the status of on, PTC is in short circuit and no voltage. When the protected equipment works abnormally, the contact switches off, and then PTC is generating heat and has voltage. The heat makes the protector keeping switch off, so resistance of PTC reaches 10KΩ, which makes the load stay in off. Only cutting off the electricity and the temperature of PTC decreased, that can make the protector reset automatically, and the load restore working normally.