[Amps] Transformer choice

[Carl]

A 105C rise is not what I consider a good transformer, ask what the 
magnetizing current is.

Carl
KM1H


----- Original Message ----- 
From: "Ulf (SM0NOR)" <ulf at sm0nor.com>
To: <amps at contesting.com>
Sent: Monday, March 04, 2013 6:28 AM
Subject: [Amps] Transformer choice


Hi Guys,
I'm looking for some feedback on two transformer offers I have. I'm 
intending to build a table top amp, so I'm accepting some compromises 
regarding the transformer. I have made inquiries to a couple of winders and 
I have boiled them down to 2 offers. I was asking for 2000 Volts @1A =2000VA 
(+ G1 and G2 windings). I'm targeting to get 2200-2400 watts output in PEP 
service and about 1K in continuos service.

Both companies claim 2000VA but at different core weights

Company A:
17 Kilo toroid,  D=200 mm, H=110. About 3% voltage drop at full load. Max 
temp rise = 105C over 40C ambient. DC resistance, about 25 ohms.
Price: €480

Company B:
11 kilo toroid, D=180 mm, H=85mm. About 2,5% voltage drop at full load. 
Can't, or don't want to specify other data.
Price: €195

So what are your reflections? The A is obviously a the better choice. They 
are serious and they offer detailed specs, exact delivery times etc. But all 
comes at a premium price. Company B is smaller and they obviously 
compromises with their specifications, but the price is a lot lower and so 
is the weight.

Now, I don't expect the cheaper and smaller core to do wonders. The bigger 
one will for sure be more rugged and closer to "true 2000VA", especially if 
I run it in true continuous mode. I'm inclined to go for the the bigger one, 
because I want the best. But OTOH, I don't want to waste money because of a 
"feeling". Perhaps the smaller one will be enough given the table-top 
size/PEP service I'm targeting? After all, it matches what's inside most 
commercial amps in this category.

I'm happy for any feedback...



73's

Ulf (SM0NOR)
ulf at sm0nor.com



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