Supply Voltage - 216 to 253 Volts????

[xAlex]

I have just measured my mains voltage at 245V. I thought that the supply should be 230V. I spoke to the distributor (NPower). They assured me that anything between 216 and 253 was acceptable. Is this correct? If so, what is NOT acceptable? I've heard that a high voltage can blow light bulbs and I have had 6 new motherboards between 2 different laptops in the last 18 months. Any connection?
Thanks.

 

[davy_owen_88]

That is correct, the permissible limits are: -6% - +10%. Anything lower than 216v and higher than 253v is not acceptable. Overvoltage can cause premature failing of light bulbs and I wouldn't be surprised if it had a negative effect on computer motherboards too.

Davy

 

[Taylortwocities]

Nominal voltage is 230v and they are allowed -6% AND +10% of 230v so teh values thay gave you are correct.
The nominal voltage in the UK used to be 240v but 245v is typical and they wont do anything about it unless its outside limits (unlikely to do much about it even then.....
.
High voltage will shorten the life of lamps. Its more likely to be spikes from somewhere. Suggest u use surge protection on your PC.

TTC

 

[systemtek]

Is your meter accurate ? Just a thought....

 

[ColJack]

oh great, it double posts, i then edit the second to appologise, and it deletes the first post.. so i lost what i said in the first place...

as i originaly said.....

it depends on how close you are to the sub station.. they output at the maximum permisable voltage.

our factory has it's own sub, and we get 252 volts at the distribution boards in there...

it allows for voltage drop on the cable runs..

and yes our meters are accurate, we have them calibrated every 6 months.

+++++++++++++++
moderator's note

I deleted your duplicate posts. System is running slow today so there have been quite a few.

Mod Rupert
+++++++++++++++

 

[plugwash]

That is correct, the permissible limits are: -6% - +10%. Anything lower than 216v and higher than 253v is not acceptable. Overvoltage can cause premature failing of light bulbs and I wouldn't be surprised if it had a negative effect on computer motherboards too.

not if the PSU is built properly it won't

 

[toasty]

Has anyone ever tried to lower their mains voltage by using the old transformer secondary in series with the mains and primary connected in the normal fashion trick?

Just say you have a 60amp supply and want to drop your voltage by 10v, get a 10v 60amp transformer (600VA so not too big) and connect the secondary in series with the incoming supply (after the meter and before the CU)

Then connect the primary across the mains.

End result you subtract or add (depending on which way you connect) the secondary voltage away from your existing mains voltage.

Anyone ever tried it? Or does anyone use it in their house - obviously there are safety considerations etc.. but its a nice simple way to affect your supply voltage.

Of course with a couple of different secondary tappings, some voltage monitoring and some big relays/contactors you could maintain a steady voltage irrespective of local variations caused by demand etc...

I've always quite fancied trying it, not least because until I saw this method I thought the only way to achieve the same result would have been a really big (in the case above ~ 15KVA) isolation transformer with a near 1:1 ratio which is obviously gonna be big and heavy and pricey.

Please again note, that this could be potentially dangerous, I'm not suggesting anyone tries it, and clearly you'd need to be mindful of the heavy currents involved and make the necesary precautions.

-Dan

 

[securespark]

Has anyone ever tried to lower their mains voltage by using the old transformer secondary in series with the mains and primary connected in the normal fashion trick?

Anyone ever tried it? Or does anyone use it in their house -

I'm not suggesting anyone tries it

 

[toasty]

Ha ha!

Yep I see what you mean.

Just trying to include the usual disclaimer.

i.e please don't do this just because I mentioned it. But if you are already doing it, I'd be interested to hear about it.

 

[toasty]

So noone is doing it then?

Tried it last night on a smaller scale, works a treat, my table lamp is now running at 230v rather than 249ish v

It'll be interesting to see how long the bulb lasts at the reduced voltage, my guess would be considerably longer.

Interesting stuff - even if it only seems that I think so!

 

[bernardgreen]

I use a Variac when essential to change the mains voltage by a few percent.

 

[plugwash]

the biggest risk is that the mains side of the transformer becomes disconnected from the mains. then the transformer will act in reverse and you may end up with thousands of volts and/or a fried transformer.

if i was going to do this i'd make sure the transformer was inside an earthed metal box and kept away from anything flamable.

 

[toasty]

Interesting points Plugwash.

Totally agree re: doing it properly, earthed metal boxes, adequately rater Xformer etc...

Regarding failure of the primary or disconnection, I'm not so sure. Given the relative impedence of the (in my case) table lamp at some 300 ohms and the Xformer secondary circa 1ohm, the most I'd expect to see on the primary is around the 200ish volts, so hopefully wouldn't damage the Xformer.

That said, I hadn't considered this, maybe a failsafe is in order, as I do intend to wind a multitapped Xformer so I can auto regulate the supply to as near 230v as poss for my critical IT systems under the stairs

Thanks for the comments, bernard I take your point RE: a variac, but I'd love to see (I really would if anyone has any pics) a 14KVA variac, my solution requires a much smaller device, but your method is probably superior for small loads.

Cheers to all who've responded

 

[bernardgreen]

the biggest risk is that the mains side of the transformer becomes disconnected from the mains. then the transformer will act in reverse and you may end up with thousands of volts and/or a fried transformer.

This does happen. one of the risks of counter wound tranformers used in this method of control. Take a 230 volt input -- 10 volt output transformer ratio 23 to 1 .

With the mains side of the transformer open circuit it becomes the secondary of a tranformer the primary of which is in series with a load and 230 volts. But as the transformer has no load its primary appears as high impedance and the full mains voltage will be across it ( less very small loss across the low by comparison impedance of the load. So 230 onto a 1 to 23 transformer provides un-loaded 5,290 volts

 

[tim west]

Has anyone ever tried to lower their mains voltage by using the old transformer secondary in series with the mains and primary connected in the normal fashion trick?

Just say you have a 60amp supply and want to drop your voltage by 10v, get a 10v 60amp transformer (600VA so not too big) and connect the secondary in series with the incoming supply (after the meter and before the CU)

Then connect the primary across the mains.

End result you subtract or add (depending on which way you connect) the secondary voltage away from your existing mains voltage.

Anyone ever tried it? Or does anyone use it in their house - obviously there are safety considerations etc.. but its a nice simple way to affect your supply voltage.

Of course with a couple of different secondary tappings, some voltage monitoring and some big relays/contactors you could maintain a steady voltage irrespective of local variations caused by demand etc...

I've always quite fancied trying it, not least because until I saw this method I thought the only way to achieve the same result would have been a really big (in the case above ~ 15KVA) isolation transformer with a near 1:1 ratio which is obviously gonna be big and heavy and pricey.

Please again note, that this could be potentially dangerous, I'm not suggesting anyone tries it, and clearly you'd need to be mindful of the heavy currents involved and make the necesary precautions.

-Dan

I'd be worried that any time critical equipment may be affected by the lag caused by the inductance of the winding and the mixing of mains borne sine wave with lagging waveform superimposed may upset dimmers and the such like that rely on accurate timing of the zero crossing to operate properly. besides affecting PF aswell. this basically sounds like a rather big version of a choke and we all know what they can do when the supply is switched on/off!