Hello, I'm looking for some advise please on using the Haas-Kamp conversion that is written up predominantly for welders. I purchased a star connected 15 kva
3-phase auto transformer to use as a motor phase converter.
In star this has the phase voltages of R1= 480,440,400,380,240 and secondary R2=220,200 and I have access to the star connection. Obviously this has the other two phase legs S1/S2, T1/T2 with the same trappings.
I want to operate this transformer in the Haas-Kamp single phase mode using capacitors on the center core of the three legs.
For simplicity and identification the transformer has three windings starting from the left .....R, S and T. With S being the centre core.
I've calculated the single phase voltages when the cores are individually powered single phase i.e. With the star point split ... lets assume this is the start of each of the 3 individual windings.
The voltage values for R1 connections now becomes " taking the star point as 0v", 115 (was 200 when in star),127,138,219,230,254,277 respectively) .To check This i applied 240 vac to 0v connection and 277 Tap connection then worked my way down to 230 connection (was marked 400 in star) and the amps drawn was 1.67amps. Tested other phases individually and got the same. ..all ok so far.
My next move was to connect the two outer windings R &T in reverse connected across the single phase, but for safety, I initially connected L 1 to 230 connection on R, and Neutral to the 0v on R winding. Then one leg of T230 connection to Neutral, and measured between L1/230 across to 0v on T winding and have got 167 volts.....? I did try reversing the connection on T winding but then got over 377 volts ...Ouch this seams way too high...Could this be as a result of not having the complete transformer with the centre transformer connected with capacitors ..so not considering the whole picture or is it a floating imposed voltage with no real power?behind it. I therefore went back to the initial reversed winding configuration of 167 volts and placed a 3 amp fuse between (L1/230,0v on T winding)...... switched on the the fuse lit up like a lamp and bang!.....
Can somebody shed any light on this please? ... as I'm seriously questioning going the next step.. which in all honesty I think I will have to do to find out but I would prefer to at least have a better inkling that it will work and that I have not done anything stupid.
When I succeed then! I'm planning to wind a separate secondary 240 volt coil over the existing and connecting it in star.. then measure the actual phase angle.to see if we have 3 phase?....it got to be worth a shot.
What should the correct size of capacitors be for 15KVA as on the single phase amps will be in the order of 81 amps?=15000/(230x0.8). But the capacitors are only in one leg 1/3rd?.