Building a transformer
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From: Dave Plowman (News) on 8 Aug 2006 19:42 In article <rm7id293e0gk1id8gf4s4fu79aboaf1oae(a)4ax.com>, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: > >What pray-tell is an RMS Watt? > >" Put out 400W RMS into 4 x 16 ohm speakers in parallel." > > > Sine wave into equivalent of 4 ohm load... 4 each 16 ohm speakers in > parallel... I think... it was 30 years ago, might have been 4 each 8 > ohm speakers... 2 ohm equivalent load. All I remember is the 400W ;-) A watt is a watt - a measure of power. So can't be qualified by RMS or whatever. Although that doesn't stop the advertising boyos trying... -- *Learn from your parents' mistakes - use birth control Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: Jim Thompson on 8 Aug 2006 19:59 On Wed, 09 Aug 2006 00:42:46 +0100, "Dave Plowman (News)" <dave(a)davenoise.co.uk> wrote: >In article <rm7id293e0gk1id8gf4s4fu79aboaf1oae(a)4ax.com>, > Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >> >What pray-tell is an RMS Watt? >> >" Put out 400W RMS into 4 x 16 ohm speakers in parallel." >> > > >> Sine wave into equivalent of 4 ohm load... 4 each 16 ohm speakers in >> parallel... I think... it was 30 years ago, might have been 4 each 8 >> ohm speakers... 2 ohm equivalent load. All I remember is the 400W ;-) > >A watt is a watt - a measure of power. So can't be qualified by RMS or >whatever. Although that doesn't stop the advertising boyos trying... I was just trying to distinguish the number from those that the "music power" types like to bandy around. For instance peak instantaneous power would be 800W ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Kevin Graf on 8 Aug 2006 19:59 Mark Fortune 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 Get a copy of the 1980 book: Practical Transformer Design Handbook Eric Lowdon Howard W. Sams & Co. book publisher ISBN: 0-672-21657-4
From: Mark Fortune on 8 Aug 2006 20:00 peter wrote: > Do you need both + and - power at the same time? If not, just have 0-50V > would save you half the power. I would need the option of both +v and -v in respect to ground, but only sometimes at the same time (ie when testing audio circuits, but not when doing logic circuits) if I switched one of the secondary windings off... would I still be saving half the power? > If you need to use 1V at 5A, your power supply would become pretty > inefficient (supplying 5W and wasting > 300W). Are you planning to fan cool > it? If not you need a huge heat sink. Wastage is becoming more apparent as I read more and more posts... and am considering rethinking to a more energy efficient design now. I was (originally) thinking big heatsink with some thermal controlled fans screwed on. > > If you use a switching design, it would be a lot more efficient. > switching psus I know nothing about, but think I will research this. Any good places to start (apart from the obvious google)?
From: ArameFarpado on 8 Aug 2006 20:08
Mark Fortune 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 Does nobody knows howto calculate transformers anymore? this will be a 600Watt transformer you will need iron of 150mm EEE and III (a standard dimension) a form of 50x54mm primary: use 1.35mm diameter wire roll 377 spirals secondary: use wire of 1.77mm diameter (if this does not exist, get the after next in diameter) weld first out line (60v) roll 104 spirals weld second out line (0v) roll 104 spirals weld third out line (60v) put the irons one by one always alternate positions tight as much as you can the irons dive it into hot varnish and let it dry this is just the transformer, i guess you will also want to pass AC to DC and maybe a voltage regulator controlled by a variable resistor, but that is another story ;) regards ArameFarpado |