What is overload protector and it's function in refrigerator and air conditioners.
A overload protector is an electrical device which we use for compressors protection, whenever the compressor temperature high form his range the compressor overload cut off the electric supply form compressor motor that's why we called him thermal overload.
The connection of overload with compressor in series and inside the overload we connect a heating resistance and with heating resistance we connect a bimetallic strip metals. The heating resistance and bimetallic strip metals both make a overload relay.
The working of overload relay is simple whenever the compressor motor getting heat up, due to the overload connected with the compressor body, the internal overload heating resistance heat up and due to heat up the bimetallic strip metals cut up the connection between one another and its make comprssor circuit to a open electric circuit. When the compressor come back to his normal state/temperature, the thermal overload protector make a close electric circuit inside, and connect the electric supply to the motor.
Note that compressor is getting heat by flowing a high amount of current, however if compressor getting normal current (Ampere) and it is heating, then also Overload protector will be trip or make open circuit if it's connected with compressor body.
The cut off the supply overload make safe compressor motor form internal winding damages/ burned. However you will not understand the working principles of overload with out a diagram. That's why i designd a diagram about the internal structure of a thermal overload protector.
In the above figure, i shown overloads 2 types and i lights it's terminals with the name of IN and Out. The (IN) means that we gave electric supply to this terminal and (Out) means that we get electric supply for compressor or we can say that this point is goes to connect the compressor common terminal.
How to find out Start,Run,Common terminals in a Compressor
I also shown a internal structure of overload in above example diagram. In diagram i shown the bimetallic strip metals with heating resistance with incoming and outgoing supply. When ever the compressor start getting high current the heating resistance heat up and create an open electric circuit.
This one of main reason that we use thermal overload protector in refrigerator compressor, i hope you will get a good information from this post, however we will soon discus the main reason of compressor getting high current or heat up.