electronic start for fridge motor?

[frank]

Hi all,

sorry for slightly OT!

A friend of mine made a very nice compressor out of a fridge compressor
motor, now this motor has a PTC kind of starter relay. The problem is
that the PTC remains in his "hot" state for some minutes after the motor
has been powered down by the high pressure relay (added externally) and
won't start when the pressure gets low again if the PTC hasn't cooled
yet. Does anyone know of an electronic substitute for the PTC? I thought
about making a small circuit with maybe a triac but I didn't want to
reinvent the wheel. I know there exist also the coil type of starter
relays, but not easily obtainable here.
Thanks in advance.

Francesco

 

On 19 Feb 2010 16:20:31 GMT, frank <frank@ottone.venere.it>wrote:

Hi all,

sorry for slightly OT!

A friend of mine made a very nice compressor out of a fridge compressor
motor, now this motor has a PTC kind of starter relay. The problem is
that the PTC remains in his "hot" state for some minutes after the motor
has been powered down by the high pressure relay (added externally) and
won't start when the pressure gets low again if the PTC hasn't cooled
yet. Does anyone know of an electronic substitute for the PTC? I thought
about making a small circuit with maybe a triac but I didn't want to
reinvent the wheel. I know there exist also the coil type of starter
relays, but not easily obtainable here.
Thanks in advance.

Francesco

A solid state PTC is going to mimick a mechanical PTC. What you need
is more along the lines of an EPR or Electronic Potential Relay. The
PTC was designed to additionally protect the compressor against a
restart attempt after a loss of power.