How a Refrigerator PTC Relay Working and FunctionIn the refrigerator compressor we use the split phase single phase induction motor and this motor have internal two types of winding which we called running and starting winding or auxiliary winding. We know that a single phase motor did not start with a starting capacitor or a staring current.
In simple words the refrigerator ptc relay gave a current to start winding and when the motor stat up the ptc compressor relay remove the start winding from the circuit.
So the above is a simple and short explanation of refrigerator relay and it's working, So lets know the working method of a PTC.
|Compressor starting relays|
As i written above that ptc mean positive temperature coefficient thermistor which means that a relay with working relation with temperature. Basically a ptc thermistor is a resistor whose resistance increase with increase of temperature.
So let's explain it step by step
We know that compressor motor or fridge compressor have split phase induction motor which have two types of winding, the main winding which we called him RUN Winding and the auxiliary winding which we called START Winding. A fridge compressor required a starting current to start normally and for this we connect the starting relay.
Compressor three terminals called START, RUN and COMMON. Common means the point where the start and run is connected.
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Internal structure of induction motor winding connection
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We connect overload protector to compressor common terminal and ptc relay to the run and start terminal. In ptc relay the supply goes direct to the run winding but between supply and start winding a thermistor is connected in series and when we switch on the refrigerator the current start flowing through the thermistor to auxiliary and compressor start up, this current flow heat thermistor and due to temperature the resistance of thermistor high and thermistor remove the start winding from supply.
E.g Example : If you start you fridge and then you switch off and then start it, you will notes that the compressor is not start again because of heat thermistor or relay. And when you switch off again and try after 5 to 10 minutes you will find the fridge compressor start normally.
In many cases we connect a staring and running capacitor to the ptc relay which help very much in staring compressor. With starting capacitor we connect ptc relay thermistor in series which make remove of start capacitor form the circuit. In many ptc compressor relay have a connection point for run capacitor and we connect the run capacitor in parallel with relay which help in better staring and running compressor.