Building a transformer
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From: Mark Fortune on 8 Aug 2006 14:20 Greetings to the collective. For my next project I want to build a bench power supply and do away with this old switch mode AT computer PSU that i'm currently using. The design I have in mind will be pretty beefy, giving a wide range of fixed and variable output voltages (i'm thinking from -50v up to +50) and deliver up to 5amps of current. if my estimates are right i'll need a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had a look at some transformers in this range, and they're a little out of my price range. so now i'm considering building my own. The specifications I need are as follows: primary: 0-230v @ 50Hz Secondary: 60v-0-60v secondary output current max: 5A I have an intermediate understanding of transformers, but have never actually built one, hence I am seeking advice from those with experience in this field. So where do I start? what type of core is best for this application? - I have a friend who's blasting off that toroids are best, but i'd like a second opinion, and what kind of wire to use for the primary and secondaries? what are good safety practices regarding insulation? Is this even a feasable project to undertake (moreso on the money side than timewise). Any other advice also greatly appreciated. regards, Mark
From: t.hoehler on 8 Aug 2006 15:01 "Mark Fortune" <mark(a)fortrex.co.uk> wrote in message news:44d8d62e$0$26602$da0feed9(a)news.zen.co.uk... > Greetings to the collective. > > For my next project I want to build a bench power supply and do away with > this old switch mode AT computer PSU that i'm currently using. > > The design I have in mind will be pretty beefy, giving a wide range of > fixed and variable output voltages (i'm thinking from -50v up to +50) and > deliver up to 5amps of current. if my estimates are right i'll need a > 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had > a look at some transformers in this range, and they're a little out of my > price range. so now i'm considering building my own. > > The specifications I need are as follows: > > primary: 0-230v @ 50Hz > Secondary: 60v-0-60v > secondary output current max: 5A > > I have an intermediate understanding of transformers, but have never > actually built one, hence I am seeking advice from those with experience > in this field. > So where do I start? what type of core is best for this application? - I > have a friend who's blasting off that toroids are best, but i'd like a > second opinion, and what kind of wire to use for the primary and > secondaries? what are good safety practices regarding insulation? Is this > even a feasable project to undertake (moreso on the money side than > timewise). Any other advice also greatly appreciated. > > regards, > Mark Not really worth the effort, IMHO. However, take a look at All Electronics, Hosfelt Electronics, MCM Electronics. There are others also. They have over run surplus trannys with really good prices. The other alternative is try to find an old high power am fm receiver which is kaput and not worth fixing. They have a transformer with the approximate outputs you seek. You're right, if you have the time, building your own power supply is fun and saves lots of loot. regards, Tom
From: Peter A Forbes on 8 Aug 2006 15:08 On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune <mark(a)fortrex.co.uk> wrote: >Greetings to the collective. > >For my next project I want to build a bench power supply and do away >with this old switch mode AT computer PSU that i'm currently using. > >The design I have in mind will be pretty beefy, giving a wide range of >fixed and variable output voltages (i'm thinking from -50v up to +50) >and deliver up to 5amps of current. if my estimates are right i'll need >a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've >had a look at some transformers in this range, and they're a little out >of my price range. so now i'm considering building my own. > >The specifications I need are as follows: > >primary: 0-230v @ 50Hz >Secondary: 60v-0-60v >secondary output current max: 5A > >I have an intermediate understanding of transformers, but have never >actually built one, hence I am seeking advice from those with experience >in this field. >So where do I start? what type of core is best for this application? - I >have a friend who's blasting off that toroids are best, but i'd like a >second opinion, and what kind of wire to use for the primary and >secondaries? what are good safety practices regarding insulation? Is >this even a feasable project to undertake (moreso on the money side than >timewise). Any other advice also greatly appreciated. > >regards, >Mark By the time you have bought the core, be it toroid or E I lams, bought the bobbin (if you use E I) bought two lots of wire, insulating fabric tape etc etc etc., you may as well go and buy the right thing. We make our own up to 3kVA, and we have all the bobbins, wire, varnish, tapes etc., but before you ask, we don't do one-offs. Most of ours are specials that we have designed by an outside consultant. Above 3kVA we go outside for them as it isn't worth keeping all the steel strip, special wire and bigger winders, varnish dip etc etc. We have a pair of winding machines plus a hand winder which we can wind up to 3mm copper wire or small rectangular tape. You may have to look around for what you want, but I promise you it will save you a lot of time and trouble. Peter -- Peter & Rita Forbes Email: diesel(a)easynet.co.uk Web: http://www.oldengine.org/members/diesel
From: Gerard Bok on 8 Aug 2006 15:15 On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune <mark(a)fortrex.co.uk> wrote: >For my next project I want to build a bench power supply and do away >with this old switch mode AT computer PSU that i'm currently using. > >The design I have in mind will be pretty beefy, giving a wide range of >fixed and variable output voltages (i'm thinking from -50v up to +50) >and deliver up to 5amps of current. if my estimates are right i'll need >a 600va+ (100v * 5a + overhead) transformer to do the job well. No, it won't :-) Your math is right. But what do you expect if you decide to draw 1 Volt at 5 amps from that beast ? Who / what is going to dissipate the 600 - 5 = 595 VA for you ? >Now i've >had a look at some transformers in this range, and they're a little out >of my price range. so now i'm considering building my own. > >The specifications I need are as follows: > >primary: 0-230v @ 50Hz >Secondary: 60v-0-60v >secondary output current max: 5A > >I have an intermediate understanding of transformers, but have never >actually built one, hence I am seeking advice from those with experience >in this field. Here's your advice: don't even think of starting at 600 VA if you want to roll your first transformer :-) -- Kind regards, Gerard Bok
From: Modat22 on 8 Aug 2006 15:38
On Tue, 8 Aug 2006 15:01:26 -0400, "t.hoehler" <t.hoehler(a)insightbb.com> wrote: > >"Mark Fortune" <mark(a)fortrex.co.uk> wrote in message >news:44d8d62e$0$26602$da0feed9(a)news.zen.co.uk... >> Greetings to the collective. >> >> For my next project I want to build a bench power supply and do away with >> this old switch mode AT computer PSU that i'm currently using. >> >> The design I have in mind will be pretty beefy, giving a wide range of >> fixed and variable output voltages (i'm thinking from -50v up to +50) and >> deliver up to 5amps of current. if my estimates are right i'll need a >> 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had >> a look at some transformers in this range, and they're a little out of my >> price range. so now i'm considering building my own. >> >> The specifications I need are as follows: >> >> primary: 0-230v @ 50Hz >> Secondary: 60v-0-60v >> secondary output current max: 5A >> >> I have an intermediate understanding of transformers, but have never >> actually built one, hence I am seeking advice from those with experience >> in this field. >> So where do I start? what type of core is best for this application? - I >> have a friend who's blasting off that toroids are best, but i'd like a >> second opinion, and what kind of wire to use for the primary and >> secondaries? what are good safety practices regarding insulation? Is this >> even a feasable project to undertake (moreso on the money side than >> timewise). Any other advice also greatly appreciated. >> >> regards, >> Mark > >Not really worth the effort, IMHO. However, take a look at All Electronics, >Hosfelt Electronics, MCM Electronics. There are others also. They have over >run surplus trannys with really good prices. The other alternative is try to >find an old high power am fm receiver which is kaput and not worth fixing. >They have a transformer with the approximate outputs you seek. You're right, >if you have the time, building your own power supply is fun and saves lots >of loot. >regards, >Tom > I had 3 toroids made by Tortran a couple years ago for a homemade audio amp, they where very reasonable. I recommend you tell them to give you a non-thermo protected primary. |