big denford triac problems

Rotary converters are fine, however you just have to be aware of their limitations.
Some equipment won't tolerate a big mis-match on voltages, but even your mains 3 phase is rarely perfectly matched. You're only likely to get problems if the false leg is majorly out of tolerance, or you are pushing equipment to it's limit.

However some rotary converters leave a lot to be desired in terms of controlling the false leg, and safety protection.

pics of the phase converter, well part of it the other bit is the previous pic with the ammeter which is not so easy to get the lid off
you can see the stop button i use for offAttachment 25166Attachment 25167