compressor starter

[star882]

I have never seen this design. Any comments?

[NoNickName]

It looks like a single phase CSR with split winding. Rotative hermetic compressors from Sanyo or other brands have a similar starter.

[walden]

It’s a single phase, capacitor motor starter. On first switch-on, there is a voltage appearing across the 4K7 resistor and this voltage switches on the triacs (the two triangles): they act like a switch and the 160uF capacitor, in the start circuit, is in operation. The motor starts with both windings in circuit. The voltage quickly falls as it leaks away through the 1uF capacitor and the triacs switch off. The motor now runs on the run winding only. It’s a solid state equivalent of the mechanical switch fitted on the motor shaft that takes out the capacitor as the motor speeds up.

[star882]

Looks like time to buy some parts and test it out (modifying it as needed). I have everything except the 0R1 resistor. I was looking for a solid state circuit to replace a worn out compressor start relay.
Only concern is that the triac might fire near the peak for each cycle during starting, thereby causing electrical stress.

I think I'll add a small choke (or resistor) between the triac and start capacitor along with a 5uF motor run capacitor from S to R to "soften" the surges.

[star882]

I just built the circuit and it works fine. It even worked for a "hot restart".