Post by thread:[EE]: 3 phase transformers

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

check http://www.pwdahl.com/ bill Sean H Breheny wrote: {Quote hidden}>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 > > > >

On 4/4/06, Sean H Breheny <spam_OUTshb7TakeThisOuTnetzero.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 > > > -

>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 ... ;)

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}>From: "Sean H Breheny" <shb7KILLspamnetzero.net> >Reply-To: "Microcontroller discussion list - Public." <.....piclistKILLspam.....mit.edu> >To: EraseMEpiclistspam_OUTTakeThisOuTmit.edu >Subject: [EE]: 3 phase transformers >Date: Mon, 3 Apr 2006 21:34:35 GMT > >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 > > >

At 11:20 AM 4/4/2006 +0300, you wrote: >On 4/4/06, Sean H Breheny <shb7spam_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@speffKILLspaminterlog.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

> -----Original Message----- > From: KILLspampiclist-bouncesKILLspammit.edu [RemoveMEpiclist-bouncesTakeThisOuTmit.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.

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}

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

Howard Winter wrote: {Quote hidden}> 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 > > Can't remember the reason why, but the voltage between 2 phases (RMS Value) is the single phase RMS value * 1.732 > Dave

On 4/7/06, Howard Winter <spamBeGoneHDRWspamBeGoneh2org.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

> 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).

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? -- Note: To protect our network, attachments must be sent to TakeThisOuTattachEraseMEspam_OUTengineer.cotse.net . 1-520-850-1673 USA/Canada http://beam.to/azengineer

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" RemoveMEspeffTakeThisOuTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com