Thermal Overload Relay Wont Reset

I hope you will find this article informative and helpful.

Thermal overload relay wont reset.

What is is and how it works. There is a motor of rating 15 kw when motor change over from star to delta the over load relay is not tripping but the mcb of 32amp in main switch room is tripping repeatedly again after switching on the mcb from mcr when i reset the overload relay the change over of motor from star to delta happening overload relay setting is 15 5 amp and time. The reset temperature is not precisely specified but the automatic thermal overload switch will reset after the motor cools down. I do not understand how this can be met when some motors have a thermal overload built into the motor that reset automatically.

All overload relays must be what is called trip free meaning you cannot hold down the reset button to override the trip function. Heater elements don t wear out they do their job. A reset button is present over the overload relay to reset the overload relay after a trip and clearance of fault. The thermal overload relay is designed to protect the motor or other load from damage in the event of a short circuit or being over loaded and overheating.

The simplest overload relay is activated by heat caused from high current flowing through the overload and over a bimetallic strip. A thermal overload relay works in the principle of electro thermal properties in a bimetallic strip. So my question is do you typically use a motor overload with all motors and monitor a auxiliary contact of the motor overload. When the rw thermal overload relays are intended to protect single phase ac loads or dc loads the connection should be made as shown in the diagrams on page 10.

It is placed in the motor circuit in such a way that the current to the motor flows through its poles. A thermal overload relay works on the heat produced by the excessive overload current the heat produced by the overload current is utilized to trip the motor circuit. Hi friends in this article i am talking about thermal overload relay working principle and its function in a dol starter. 4 thermal overload relays rw line applications rw thermal overload relays have been designed to protect three phase and single phase ac motors and direct current motors1.