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Old 22nd January 2009, 08:13 PM   #1
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Default Weight differences of transformers

Please help me to choose the right toroids for my poweramps.

How can there be as big differens in weight for the same VA ?

Both are 500VA, prim 230V, sek 2x35V, 2x7,14A.

Multicomp from Farnell, partnr:9532552, 4,3 kg.

Nuvoterm from RS, partnr:223-8279, 3,5 kg, (a little bit cheaper).

A differens of 0,8 kg, is it possible and how does that influence performance ?

Which should i go for, which could be the best one, for my purpose ?
Im going to buy four pieces, so its important to do the right choice.
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Old 23rd January 2009, 07:21 AM   #2
Elvee is offline Elvee  Belgium
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There might be a number of reasons for this difference:

-The heavier one has a more conservative design, more iron and copper.

-The lighter one uses more advanced technologies and materials: high performance magnetic alloy, space-saving winding techniques.

-Both are in fact identical, but have a different design: f.e., some transformers have a cast resin center instead of mounting flanges.
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Old 23rd January 2009, 10:27 AM   #3
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Thanks Elvee

But its a weight difference of 20%, nearly 1 kilo, of a pice weighing 4 kg.
It must be some real big difference in performance.

In a power supply for a highwatt amplifier, the transformer has to work in short dynamic swings and one of these must be the right choise.
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Old 23rd January 2009, 11:20 AM   #4
Elvee is offline Elvee  Belgium
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Anyway, weight seems a strange selection criterion. Did you choose your girlfriend in the same way?
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Old 23rd January 2009, 02:55 PM   #5
MondyT is offline MondyT  United Kingdom
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Hi Ragnwald

The Farnell transformer has a tighter regulation than the RS version, so there is your extra weight.

I would go for the transformer with the tighter regulation as a general rule, but this decision could be heavily influenced by what voltages you want to get out of your power supply circuit etc. Better regulation in the transformer means better regulation on your DC voltages

Cheers
Ray
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Old 23rd January 2009, 05:04 PM   #6
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Elvee, that means ill go for the big one.

MondyT, thanks for that information.
Do you have any links to read more of the matter?
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Old 24th January 2009, 07:50 AM   #7
MondyT is offline MondyT  United Kingdom
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Hi Rag

Some good information can be found here...

http://sound.westhost.com/xfmr2.htm#11-losses

Look under regulation, but there is plenty more transformer info to get your teeth into, should you be interested

One thing to look out for on your travels, the simple txfrmr regulation definition can be expressed differently. In the USA and other places it is defined as...

(Vnl - Vfl) / Vfl %

where Vnl= no load secondary voltage
and Vfl = full load secondary voltage

Where as in the UK it is defined as...

(Vnl - Vfl) / Vnl %

Hope this helps

Ray
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Old 24th January 2009, 09:00 PM   #8
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Thanks MondyT, you put me to the essence.
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Old 24th January 2009, 09:25 PM   #9
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Here's a good walkthrough of the process of designing an OT, with some comments on how it relates to a power transformer:-

http://www.geofex.com/Article_Folder...es/xformer.htm

w
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Old 25th January 2009, 01:53 PM   #10
star882 is offline star882  United States
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Don't forget frequency either. It makes a *very* substantial impact on weight.
Case in point: the transformer in a PC power supply is rated for hundreds of watts but weighs less than a pound as it operates at a high frequency.
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