I agree with you that the choice you made was a very good one and I'm happy to hear that those voltage elevating converters, who are only offered in UK, are well working, as I was wondering whether it might be practically a good choice to buy one.Hi,
I can only answer in english, sorry.
Hoping you can understand...
I have a Schaublin KD2 motor for my SV70. It is a Dahlander motor with two possibilities: 220V tri for the slow speed and 380V tri for the high speed.
Using a classic inverter will transform 220V mono to 220V tri, so it is only possible to connect to the slow speed for a correct torque. You can adjust the frequency to 100Hz to get the high speed but with a poor torque and not sure if the motor would like it...
Connecting the classic inverter to the high speed will work but with a poor torque too.
That's why I have bought the Drives Direct inverter (about 300 euros for a 750W motor) which transform 220V mono to 380V tri.
I've connected it to the high speed without loosing torque and I can get the slow speed by setting the frequency to 25HZ without loosing torque too.
This is the best way to use a Dhalander motor with 220V mono.
More than this, playing with the stepped pulleys, I can adjust precisely the speed of my headstock from about 50rpm to 3000rpm.
Though I disagree about your explanation of the Dahlander connection: this poling is made for working both ways with strict 380V and even with the slow speed you are loosing power and torque (with the high speed poling you loose more power and more torque). I agree that with the low speed it is possible to work: that is what I am doing since one year now.
Another choice could be to have the motor re-wired for 220V and, as the 220V windings will need more volume than possibly available, this could be solved by using the double number of available coils, connecting them serially thus loosing the double speed capability.
As I already have a 220V inverter, which makes the double speed un-necessary, this could be possibly a less expensive solution compared to the purchase of another, more expensive, inverter.
For the time being, due also to the little size of the works I'm presently carrying out on my Schaublin 102, I keep working with lower torque.