PTC - Compressor starter - Positive Temperature Co-efficient
Hey, simplicity works but it has its limits
The most cheapest compressor starting device, and can I say it is not a relay , more a resistive switch.
For very small class capillary system refrigerator, usually a bar fridge or cubic fridge enter the PTC.
Now these are not high tech, and they need to have decent intervals in time before starts so they can cool down.
Also the system must equalise pressure between the high and low sides to allow for a low compression start.
The PTC starter is similar to the potential relay not by design but where the start winding is engaged immediately from first power up. . At start up the PTC is cool and has no opposition to current flow by a preset low resistance which is in series with the compressor start winding.
The compressor starts by resistive start and induction run, as the current flows through the PTC , it heats up increasing its internal resistance until it will not allow more current to flow , disengaging the start winding. The start winding is isolated and will not engage further as a trickle of current to the start winding will maintain heat and high resistance during the operation of the compressor.
When the unit stops the PTC MUST!!! cool down to allow current to flow again on next start-up. If it trys to start to early the internal overload will activate in the compressor.
So it really is not designed for frequent starts and requires very low starting torque.
Don't expect too much , price and capacity dictates control, yet I do like how simple these are.
The PTC is small, no bigger than a 10c (Australian) coin and as about 4mm thick.
Note also the compressor terminals are inverted to this design as per the Danfoss types. I have marked them.
These starter types are typically only used on low capacity, low torque compressor where off cycle pressure equalisation occurs , as you see in capillary systems
Now does anyone see a Star Trek logo on the PTC relay disc in the pictures above? , or am I just seeing things :D
All comments require moderation before they will be posted. This may take up to 24hrs, thankyou for your patience.