Rotoverter: RV Resonance Recovery Test Circuit - Half Diode Plug Across Run Cap

C1 is shown as 36uF as optimised to my particular motor. The normal range is around 17-24uF for normal RV operation.

The values C2 and C3 can be increased with experiment to see when the resonance is killed and the diode plug begins to draw increased load from the RV.

1. I have found that many new thyristors are FAULTY (around 50% in my experience so far!). They can be short circuit across A and K, or they can fail to avalanche properly when turned on, or just turn on by themselves. A working thyristor should remain on until either a negative pulse at the gate, or no more voltage across A-K. Because the function and timing of the thyristor in this circuit is critical, I recommend testing each thyristor. Here is a Thyristor/Triac test ciruit;

I have found that part selection of the thyristor is important, because some seem to turn on by themselves.

Also, an inline 5 amp fuse on the +ve terminal of the charge battery is a good idea for safety and peace of mind.

2. Powering-up the circuit. I prefer to have all the wire connections to the battery and thyristor in place before power up because there are violent sparks when connecting/disconnecting these while the RV is running (even if thyristor is turned off). If you want to turn on off the circuit in operation, use toggle switch SW1.

3. Start with VR1 (10 turn pot) in the fully CCW position, so that the Neon doesn't light at all. Then gradually turn VR1 CW until the Neon begins to flash occasionally. There should be no increased load on the RV, and no increased power consumption. You can tell by the speed/sound. If there is, then back off VR1 and re-check. If you succesfully notice no increased load, then continue turning VR1 CW so that the Neon remains lit all the time. You should see the voltage across the charge battery increase without any loading effects on the RV. The behaviour of the charge battery depends on it's initial charge condition. This is like a Bedini charger on steroids.

4. If using scope probes on this circuit, remember that there is no ground reference and it is not isolated.