Hi everyone! What a response! If this site had been available 25 years ago, I would now be CEO for General Electric! The amount of information out there is extraordinary! Solid, down to earth sensible advice from hands-on engineers! Many thanks!
Is my client an engineer? Yes, but he has to employ a Consultant or is not! To the Consultant, all electrical loads should be balanced hence: three phase good and single phase bad! This is to be a small control panel to go on an oil rig. Five, three phase pump motors (DOL) and some little single phase fan motors and about 500 W of single phase trace heaters. The transformer will go on the wall beside the panel. The position is in a non-explosive area, nothing special about the control panel, we’ve made them before. The Consultant’s fee may well be larger than the cost of the control panel!
I have only seen a Le Blanc transformer connection in text books! If I could sell that to my client it would be a first! But should I not protect him from the Consultant by offering the simpler 480/230 volt single phase transformer which will be cheaper and can, if needed, be rewound or replaced anywhere from Alaska to the Persian Gulf? Or do I sigh and buy in an expensive transformer while cursing, under my breath, all ignorant Consultants?
Thank you all very much again for your responses. You have revived my faith in engineering.
Martin Pyke.