how to wire a transformer 220 - 110v

[squazy84]

OK, if it's your own, then it's up to you.
Any issues and you will only have your insurers to answer to.
Your family might be concerned about the non-isolating scenario if things go wrong and it kills you though.
These things are designed and specified that way for a reason.
What is the EFLI at the machine incoming supply Vs the circuit OCPD?
Does this comply with BS7671?
Are you sure that the contactors you have will be OK by being supplied by an Auto Tx?

will you come over and fix it all for me please, ill give you all the tea you can drink, to be brutally honest your lucky im even using relays. this thing is a milling machine, it can kill you in so many ways its not even funny, hand in the wrong place and bang now you have no arm, almost everything in my place of work can kill me, the most dangerous are some of our customers. ive been around the place for over 25 years and still have all my digits, not been electrocuted,electrically the mill is one of the safest items there

 

[Sidewinder]

I don't drink tea!

I am seeing a LOT of smaller companies being pulled by their insurers on electrical stuff now, more and more every year.

I also know what a small milling machine is like, I have a Bridgeport.

I still say that the electrical side is more dangerous than the machine itself.
You can see the machine coming for you.

You may find that an Auto Tx will stuff up the relays for you though.

 

[rtbcomp]

The problem with an auto transformer is if the neutral becomes disconnected or if it burns out between the output and neutral, then the output will sit at mains voltage. An isolating transformer will fail safe.

Paradoxically, if the output of an auto transformer leaks to the chassis of the machine it will trip an RCD, whereas if the output of an isolating transformer finds its way to the chassis the RCD won't trip.