Insta controls manufactures thermistor protection relays [tpu], which are used alongwith ptc thermistors for over-temperature protection of electric motors, transformers and other equipment. The tpu has 2 nc and 1 no potential-free relay contacts. The no contact is used is series with starter/contactor nv coil to shut off the motor when it get hot. The nc contact can be used for indication of over-temperature. The tpu uses the signal of ptc thermistor for contact changeover. The same tpu can be used for any temperature of ptc thermistor. These relays are suitable for din rail mounting as well as chassis mounting and can be easily used in the panels as they are very compact. For continuous processes in which sudden tripping of the motor is not acceptable, the company has a dual type of thermistor protection relay. This dual tpu uses the signal of ptc thermistors oftwo different temperatures. The lower temperature signal is used for giving an alarm and if no corrective action is taken then the motor will trip when the higher temperature is achieved. These relays are available for a wide range of input ac and dc voltages. The price of any other protection system is proportional to hp rating of the motor, whereas the price of tpu is constant for all motros and is much lower than that of conventional protective systems. Thus the tpu along with ptc thermistors prevents any motor/equipment from burning at a very low cost.
