Transformer

[hareng]

Can anyone help quickly.

I have a 240V single ph supply, live goes to 0V on transformer, neutral input to 240V on transformer. This is untouched and as supplied.

One output labelled 110V gives out 126V
The other output labelled 0V gives out 252V
Reckon transformer shot?

Without power feed connected transformer hums away. Soon as a connection to the 0V output is made it throws the main RCCB in consumer unit but no fuses.

Thanks Jon.

 

[rtbcomp]

Is this a Yellow transformer used to power 110v tools off 240v or what?

What are you measuring voltages with respect to? ie where have you actually connected both leads of your meter?

Why does the transformer hum when it isn't connected to a power feed? Don't say because it doesn't know the words!

 

[hareng]

Thanks RT, Its a transformer to power a power feed on miller.

240V input 110V output 50/60Hz

Connected direct to the input and outputs on transformer.

Its always made a slight hum when powered on.

 

[rtbcomp]

.......

Without power feed connected transformer hums away. Soon as a connection to the 0V output is made it throws the main RCCB in consumer unit but no fuses.

Thanks Jon.

So you mean hums WITH the power connected? Or by power feed do you mean the feed to the machine from the transformer rather than the power feed to the transformer?

Can you measure the resistance between the primary and secondary, or is it an autotransformer?

 

[penfold]

Could you post a picture? You should have something like this.

 

[hareng]

See if this works.

Top orange connectors giving 126V
Top Grey 252V which equates to input voltage. Should be 0?

Powered on just meant switching on at mains 240V feed.

US type 3 pin output connectors so have hard wired in, taken out here.

 

[rtbcomp]

This very strange. I don't see why they say connect the live to 0v input.

Connecting anything to the 0v output shouldn't cause the RCD to trip, again, suggest you see if there's a short or partial short between primary and secondary.

 

[hareng]

Thats untouched since bought RT and how it came.
Must have been using like that 8 years and first thing i noticed when fetching the box out.

 

[Wedg1e]

Doesn't actually matter which way round you apply Alternating Current...

what might cause a problem is if you have other wiring on the machine that is conected the 'right' way round and you've tried to take a common neutral from somewhere so you end up with an anti-phase situation... just thinking about issues we have with high-voltage transformers if you reverse the start and end connections on a pair of them.

 

[rtbcomp]

^^

In general terms it does if you have fuses, single pole switches, embedded thermal cutouts and suchlike. They should be in the live side for safety.

 

[madkayaker]

The inputs conductors are incorrectly wired and this might be why you have 230v ish on 0v on secondary correct the worrying fault on primary then measure on secondary and go from there. It is imperative all fuses etc are in live conductor

 

[Robotstar5]

What voltage do you read between the grey & orange terminals at the top?

 

[voipio]

It sounds to me that you have an autotransformer and it happens to be connected the wrong way round. With all inputs and output disconnected from the transformer, what is the measured resistance between the the input and output windings. If they're separate, the resistance should be that of the insulation between the windings and should be high, as in a good few megohms. On the other hand, if there is only a fraction of an ohm between input 0 and output 0 that would suggest the two are directly connected, either intentionally or because of a fault. When operating, what is the voltage between input 0 and output 0?

 

[shenion]

Sounds like one side of the output is connected to ground. So you will get voltage relative to the input voltage.

WOuld seem normal to get 120/240 relative to the input voltages. Just may be a bit odd the hot lead is connected to 0 in the input but it really should not matter.

 

[brightspark]

if your getting 240v across the output o volts that means its conected to the primary o volt input that would cause current imbalance and trip the rcd the secondary coil should be isolated from the primary by rights . 0 volt is generaly the neutral feed and 240v the live but that wouldnt cause the rcd to trip

 

[hareng]

Thanks all for some answers i will wire the input as it should be and take it from there.

 

[MattF]

You've obviously had this running fine as is for a good length of time, by the sounds of it? If so, have you added or changed anything recently? If not, likely a winding else connected equipment fault unless you have moisture problems or similar somewhere.

 

[hareng]

Just rewired the input and changed brown and blue over. Now brown goes to 240V and blue to 0V

Voltage across the 110V and 0V outputs is 114V
Earth to 0V output 0.21V
Earth to 110V output 114V

This sound good?

Yesterday before changing over input wires i did remove the two brushes in power feed, it still tripped.

 

[madkayaker]

That's more like it!

 

[shenion]

Disconnect the input and measure resistance between the 0 and 240 terminals and earth. There should be no connection (very high resistance.) There should also be high resistance between the input terminals and the output terminals.

If any measurable resistance is found, the transformer would probably be bad.