how to wire a transformer 220 - 110v

[squazy84]

Im powering some relays on a milling machine using a 220 - 110 volt transformer, the transformer has 6 connections and it has me confused! the transformer in question is an rs 500va auto transformer 50/60 hz
207-071
roughly below its terminations it has the following notations,
240v 220v 200v N 115v E
i just require a simple 110 v supply
can anybody point me in the correct direction?
thanks for your time

 

[rtbcomp]

Assuming your mains is 220v connect your mains across 220 and N and take 115 volts from 115 and N

You can reduce the output a bit by connecting your 220v across 240 and N.

E is the earth.

 

[500e]

Like rtb said

 

[squazy84]

cheers lads that's how i have her wired i was just hoping not to trip the power in the house lol

 

[squazy84]

plugged her in and im getting 126 volts out now. thanks for your help, ill upload a picture of my real problem now in a min, it makes my head sore!!

 

[the snooper]

also be aware that it is a non isolating transformer

 

[squazy84]

here is where were at

 

[squazy84]

the above gubbins is for a 3 phase milling machine running all 3 phase motors, the power feed has its own start and stop buttons on the machine, ive taken this home to see if i can make sense of the wiring, it was taken apart by a previous owner and he unfortunatly never got to refit it

 

[the snooper]

I take it your mains is 240 if you've wired it to 220 and getting 126 out

 

[squazy84]

please excuse my lack of properly coloured wired its all thats in the house at the moment, once ive figured it out that will be put to rights.

 

[squazy84]

yes thats my thought on the matter snooper

 

[Fintray]

Not 100% sure but it looks like the relays provide a star to delta changeover for starting the main motor.

 

[rtbcomp]

I take it your mains is 240 if you've wired it to 220 and getting 126 out

115 * 240/220 = 125.45454545454545454545454545455

Close enough for jazz!

 

[squazy84]

yea , i wired it all up yesterday and she works fine, i was wondering about the harrison horozontal mill I have though as it seems i need a method of reversing the table feed motor

 

[Sidewinder]

That auto tx is not really safe or suitable for control btw.

As far as the wire colours go, what's wrong with red?

 

[squazy84]

That auto tx is not really safe or suitable for control btw.

As far as the wire colours go, what's wrong with red?

why is that?

 

[Sidewinder]

Do you understand the characteristics of an auto tx, and, in the pic it states that it is NOT an isolating tx.

One of the PRIMARY reasons for using a control tx is for isolation of the control circuit from the mains supply for safety reasons.
Also, if you are doing this for someone else as part of your business, then you cannot use an auto tx as that could be shown to be against statute law requirements in Europe, and you must use primary and secondary circuit protection on the Tx.

Nothing wrong with red for ac control, that is the standard colour.
You must not use "BS7671" phase colours in a machine control panel as that does not comply with the statute law requirements for machinery.

 

[squazy84]

its my own i did understand the non isolating bit but just dont care about it. this is my machine. only I will use it, there is more to worry about with the 380volts and an all metal machine then the auto tx, the machine has a good strong earth and an rcd breaker its the best its getting at the moment.

 

[Sidewinder]

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?

 

[Wendelspanswick]

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?

I know your trying to be helpful but we have had this conversation before. In best practice all requirements for safety/legislation are followed. In real life, especially in a DIY or one man band situation best practice is not always followed and preaching legislation is not going to change that no matter how well intentioned you are.