Re: [Amps] Transformer in GLA 1000 B : OK for 2xGI 7 ?

[craxd <craxd1@ezwv.com>]

Steve,
It does. A transformer needs to be sized for the intended circuit. A 
doubler circuit requires more current than does a bridge rectifier, 
actually more than X2 because of the arrangement. I think it is more 
like 2.6 if I recall. I've been designing transformers for numerous 
people here lately and most don't understand that the circuit they go in 
determines a lot of how the transformer is designed. There's several 
formulas to use for maximum current required by the transformer for each 
configuration. When requesting a design, you need to include the 
voltage, current for each winding, frequency, duty cycle, and the 
circuit it is to be used in. A lot of times, the transformer house will 
catch things not kosher and advise a change.

The transformer in mention, I think is rated at ICAS which would be 
about 1/2 the needed current for 100% duty cycle. The transformers 
output current rating was designed around a bridge rectifier if I 
recall. If so, the current required will be something like 2.6 times 
what it will produce in a bridge rectifier circuit. No matter what, the 
wattage required has to equal in both the secondary and primary. 
Actually, it's more than this, including losses of about 5%, but for 
sake of explanation, wattage in = wattage out. I'd hate to see somebody 
go to all that trouble of building that circuit, only to find the 
transformer smoke in a short while. If I knew the cores tongue width and 
the depth of the core itself, I could estimate the required wattage 
really quick. Even though there may be enough core, will the wire be big 
enough to handle the currents required?

Will Matney


On Tuesday 05 October 2004 02:38, craxd wrote:

>> Hello,
>> Keep in mind that when you use a doubler circuit, you will cut the
>> available current in half. The transformer wattage will always stay the
>> same. The GLA 1000 runs at about 1100-1200 Vdc with about 400-450 mA
>> available. Doubling it will only net you about 200-225 mA at 2200-2400
>> Vdc. No matter what, about 500 watts.

I think you end up with higher peak and RMS currents in the transformer,
leading to a lot extra heat in there.

I don't have time right now, but the Duncan Amps PSU designer will 
predict the
numbers.

Steve
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