Denford Triac VMC with ATC Conversion / Fix

[m_c]

You probably need a starting cap and a run cap. I actualy use a little timer that switches the start cap in for about one second, but the value of the caps you use is dependant on the motor power and if the motor is stating under load etc.. This system does not give a true 3ph, but a "quasi" 3ph, however for a coolant pump I am sure it that you will never know the difference. G.

One thing to be aware of when using this method, is you have to select caps that will provide reasonably matched voltages between the 3 legs when running. Achieving that with a small motor may prove to be a bit of a challenge, but you should benefit from the fact a coolant pump should have a reasonably steady load.
My main concern would be that the coolant pump motor is running near it's rated capacity, and when running from a static phase converter you risk burning out the motor if you try running it at high loads.

[GEOFFREY]

One thing to be aware of when using this method, is you have to select caps that will provide reasonably matched voltages between the 3 legs when running. Achieving that with a small motor may prove to be a bit of a challenge, but you should benefit from the fact a coolant pump should have a reasonably steady load.
My main concern would be that the coolant pump motor is running near it's rated capacity, and when running from a static phase converter you risk burning out the motor if you try running it at high loads.

I totally agree with the above comments and would add that I check the voltages on each leg and try to get equal voltages under normal load conditions. The run cap value will be determined by balancing the "leg" voltages, and the start cap value (which is usually only switched in for 0.5-1.0 seconds) will assist the motor to start to turn. G.