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'[EE]: 3 phase transformers'
2006\04\03@173528 by Sean H Breheny

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Hi all,

I have some high-power battery chargers which run on 480V 3 phase power. I need
to be able to make them work in England, where I believe the standard 3 phase
service voltage is 410V (please correct me if I'm wrong).

These chargers can handle 50Hz instead of 60Hz, but they cannot work down at 410
V. So, I need a transformer which takes 410V and gives me 480V. Does anyone here
know of a company which makes such devices? I'd be looking at around 20 amps in
each phase.

Thanks very much!

Sean


2006\04\03@215015 by William Jacobs

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check
http://www.pwdahl.com/
bill


Sean H Breheny wrote:

{Quote hidden}

2006\04\04@042053 by Vasile Surducan

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On 4/4/06, Sean H Breheny <spam_OUTshb7TakeThisOuTspamnetzero.net> wrote:
> Hi all,
>
> I have some high-power battery chargers which run on 480V 3 phase power. I need
> to be able to make them work in England, where I believe the standard 3 phase
> service voltage is 410V (please correct me if I'm wrong).
>
> These chargers can handle 50Hz instead of 60Hz, but they cannot work down at 410
> V. So, I need a transformer which takes 410V and gives me 480V.

Sean, not a transformer but a self-transformer (autotransformer).
Will be smaller and cheaper.

greetings,
Vasile


Does anyone here
> know of a company which makes such devices? I'd be looking at around 20 amps in
> each phase.
>
> Thanks very much!
>
> Sean
>
>
> -

2006\04\04@061844 by Alan B. Pearce

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>I have some high-power battery chargers which run on
>480V 3 phase power. I need to be able to make them work
>in England, where I believe the standard 3 phase
>>service voltage is 410V (please correct me if I'm wrong).

Might be 415 (230V per phase). But that difference shouldn't be a worry.

>These chargers can handle 50Hz instead of 60Hz, but
>they cannot work down at 410 V. So, I need a transformer
>which takes 410V and gives me 480V. Does anyone here
>know of a company which makes such devices? I'd be
>looking at around 20 amps in each phase.

Wow, that is going to be some fast charger ... ;)

2006\04\04@065052 by Sean Schouten

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On 4/4/06, Alan B. Pearce <.....A.B.PearceKILLspamspam@spam@rl.ac.uk> wrote:
>
>
> Wow, that is going to be some fast charger ... ;)
>

Probably the type used to charge up forklift trucks and other similar
electrical equiptment.

2006\04\04@091210 by Darrell Wyatt

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part 1 1468 bytes content-type:text/plain; format=flowed (decoded quoted-printable)

Hey Sean,

You'd probably be better off if you found out what the secondary voltage
of the transformer yields at 480v primary.  Then replace it with a more
appropriate transformer instead of the intermediate.  I'm thinking that the
intermediate would still be costly due to the amperage issues involved with
battery charging - Also, depending on the ratio, it may turn out to be a
negligible difference that could be accomodated in the rectification and
regulation circuits.  Of course, you would be operating "outside" the OEM
spec's -

Good luck!
D.


{Quote hidden}

>

2006\04\04@131305 by Spehro Pefhany

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At 11:20 AM 4/4/2006 +0300, you wrote:
>On 4/4/06, Sean H Breheny <shb7spamspam_OUTnetzero.net> wrote:
> > Hi all,
> >
> > I have some high-power battery chargers which run on 480V 3 phase
> power. I need
> > to be able to make them work in England, where I believe the standard 3
> phase
> > service voltage is 410V (please correct me if I'm wrong).
> >
> > These chargers can handle 50Hz instead of 60Hz, but they cannot work
> down at 410
> > V. So, I need a transformer which takes 410V and gives me 480V.
>
>Sean, not a transformer but a self-transformer (autotransformer).
>Will be smaller and cheaper.

For single-phase transformers called "buck-boost" are sold for this kind of
small
adjustment of voltage (and of course they have a relatively small and light
size
for the total output power). I don't know if 3-phase types are available or if
you'd have to use three of them. An industrial electrician should know (sounds
like a forklift battery charger or something of that ilk).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
@spam@speffKILLspamspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2006\04\04@144121 by Mike Hawkshaw

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> -----Original Message-----
> From: KILLspampiclist-bouncesKILLspamspammit.edu [RemoveMEpiclist-bouncesTakeThisOuTspammit.edu]On Behalf
> Of Spehro Pefhany
> Sent: 04 April 2006 18:23
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE]: 3 phase transformers

> For single-phase transformers called "buck-boost" are sold for
> this kind of
> small
> adjustment of voltage (and of course they have a relatively small
> and light
> size
> for the total output power). I don't know if 3-phase types are
> available....

Yes three phase versions of this type of transformer are available. We have
a 4kW 480v -> 3Kv 3 phase transformer which is fed with a 415v to 480 volt 3
phase auto transformer to step down the input. The auto transformer is much
smaller (guessing about 6 times less heavy) than the main one.

The reason being that the magnetic (iron) circuit in an auto transformer
only has to deal with the bit left over from the ratio of the two currents
in the input and output windings. For 480v -> 415v the current ratio would
be 480/415 = 1.16. The "bit left over" would be 0.16 and as a percentage of
the whole this would be a factor of about 6. That's only the magnetic core
though - the copper circuit has to pass all the current, of course.

Auto transformers do not have any voltage isolation from input to output,
beacuse you never get a free lunch.

Regards....Mike.

2006\04\05@030725 by Steve Smith

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With the transformer in the charger ensure it has been designed with 50 and
60 Hz in mind or it will get too hot (typically 60Hz transformers are 10%
smaller) but are designed for the same temperature rise.

Auto transformers are available for 3 phase we use an one rated at 80 kva
step up and down by 15% its about the size of a 20kva.

UK mains is specified at 400V +10% -6% (415)according to G5-4 until
unification of Europe at 400V +6% -10% (380) the final European voltage
should be 400V +- 6%

Rgds Steve

Battery charger/UPS manufacture Bristol England
http://www.pbdesign.co.uk


{Original Message removed}

2006\04\05@134838 by Peter

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On Tue, 4 Apr 2006, Alan B. Pearce wrote:

> Wow, that is going to be some fast charger ... ;)

I guess it depends on the size of the batteries ... could be days or
weeks to even notice a charge in a real big battery at that rate.

Peter

2006\04\07@130857 by Howard Winter

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Alan,

On Tue, 4 Apr 2006 11:18:38 +0100, Alan B. Pearce wrote:

> Might be 415 (230V per phase). But that difference shouldn't be a worry.

I always thought our 3-phase mains was at 440V (when 1-phase was 240V) - how do you get from one to t'other?

(Bearing in mind our system is Wye-wired, with Neutral in the middle, and 230V (now, nominally) from Neutral
to each phase).

Cheers,



Howard Winter
St.Albans, England


2006\04\07@135149 by Dave Wheeler

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Howard Winter wrote:
{Quote hidden}

Dave


2006\04\08@025849 by Vasile Surducan

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On 4/7/06, Howard Winter <spamBeGoneHDRWspamBeGonespamh2org.demon.co.uk> wrote:
> Alan,
>
> On Tue, 4 Apr 2006 11:18:38 +0100, Alan B. Pearce wrote:
>
> > Might be 415 (230V per phase). But that difference shouldn't be a worry.
>
> I always thought our 3-phase mains was at 440V (when 1-phase was 240V) - how do you get from one to t'other?
>
> (Bearing in mind our system is Wye-wired, with Neutral in the middle, and 230V (now, nominally) from Neutral
> to each phase).

Howard, this system ( 4 wires) is used only for low voltage
distribution on 0.4KV and not just in England but worldwide.
The load could use neutral or not depends on the wiring scheme, it has
a tipical definition as star load or triangle load. So also the
transformer could be a triagle-triagle, triagle-star or star-star
(there are many more wiring schemes except those most common )

greetings,
Vasile

2006\04\10@045942 by Alan B. Pearce

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> Can't remember the reason why, but the voltage between
>2 phases (RMS Value) is the single phase RMS value * 1.732

Wether it is star or delta connection, the voltage between
any two phases will be Vrms(Sin(a) + Sin(a + (2pi/3)))
which would look to come out to about 1.732 when a = pi/2
(i.e. Sin(a) = 1).

2006\04\10@052834 by Bob Axtell

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Alan B. Pearce wrote:

>>Can't remember the reason why, but the voltage between
>>2 phases (RMS Value) is the single phase RMS value * 1.732
>>    
>>
>
>Wether it is star or delta connection, the voltage between
>any two phases will be Vrms(Sin(a) + Sin(a + (2pi/3)))
>which would look to come out to about 1.732 when a = pi/2
>(i.e. Sin(a) = 1).
>  
>
Isn't it amazing that all those equations were worked out by Nikola Tesla
in 1910?

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2006\04\10@094220 by Spehro Pefhany

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At 09:59 AM 4/10/2006 +0100, you wrote:
> > Can't remember the reason why, but the voltage between
> >2 phases (RMS Value) is the single phase RMS value * 1.732
>
>Wether it is star or delta connection, the voltage between
>any two phases will be Vrms(Sin(a) + Sin(a + (2pi/3)))
>which would look to come out to about 1.732 when a = pi/2
>(i.e. Sin(a) = 1).

Or, to put it another way, if I did this right before my first coffee..

let the line-to-neutral voltage v(t) = Vpk*sin(w*t), then the difference
between two phases will be

vd = Vpk*(sin(w*t+pi/3) - sin(w*t-pi/3))    using trig sum/diff identities
  = Vpk*(sin(w*t)*cos(*pi/3)+ cos(w*t)*sin(pi/3) -
sin(w*t)*cos(pi/3)+cos(w*t)*sin(pi/3))
   = Vpk * cos(w*t) * K
     where K = 2 * sin(pi/3) == sqrt(3) ~= 1.73205

Vpk is peak voltage line-to-neutral
w is frequency in radians/second = 2*pi*f

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
RemoveMEspeffspamTakeThisOuTinterlog.com             Info for manufacturers: http://www.trexon.com
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2006\04\11@141500 by Peter

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> Isn't it amazing that all those equations were worked out by Nikola Tesla
> in 1910?

Tesla invented the 2-phase induction motor and advocated 2-phase ac ?:

http://www.3phasepower.org/2phasesystems.htm

Peter

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