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denny9167 15th January 2012 03:24 PM

Power Transformer Question
 
I'm considering a transformer for a project requiring 400mA of current(Edcor)
but the closest one they have in stock is 325mA. How much of an effect in power output will this have? I will enquire for a custom wind,but not sure of the cost difference. Thanks

KatieandDad 15th January 2012 03:48 PM

If you use an underspecced transformer, you can expect early failure.

The transformer will do its best to supply what you are asking but it aint big enough.

If cost is an issue, try using modern smaller transformers in seies.

flatheadmurre 15th January 2012 03:48 PM

The transformer might overheat.

When loading hard the output voltage will drop.

400mA isn´t a to big current must be a standard unit available some where ?

What specs do you need ?

DF96 15th January 2012 03:56 PM

For a rectified supply you may need a bigger transformer than you think.

M Gregg 15th January 2012 04:49 PM

Quote:

Originally Posted by denny9167 (Post 2863132)
I'm considering a transformer for a project requiring 400mA of current(Edcor)
but the closest one they have in stock is 325mA. How much of an effect in power output will this have? I will enquire for a custom wind,but not sure of the cost difference. Thanks

You need to give more information..

What is is powering...(OK its a project)..what part of the project B+ heaters power amp pre-amp...Voltage required...type of rectifier..etc..

The reason is..

If you under spec you will get sag..then it will run hot and the sound will be "bad" because it will clip early...great for a guitar amp (overdrive)..
It could blow open with inrush at start up with cold heater elements or capacitor inrush..

Regards
M. Gregg

Rundmaus 15th January 2012 05:10 PM

More information on the planned PS design is needed, if you plan for capacitor input, you'll need significantly more current capability due to the sharp current spikes charging the first cap. With choke input, the AC current capability does not need to be higher than the DC current you want to get from it, and so on...

So please, more details! ;)

Greetings,
Andreas

EDIT: I always tried to avoid custom wind, but ordered my first custom-wound transformer last year and was very pleased with it. You get exactly what you need, and (at least here in Europe) for a price that is acceptable.

Alain Poitras 15th January 2012 09:31 PM

Quote:

Originally Posted by denny9167 (Post 2863132)
I'm considering a transformer for a project requiring 400mA of current(Edcor)
but the closest one they have in stock is 325mA. How much of an effect in power output will this have? I will enquire for a custom wind,but not sure of the cost difference. Thanks

Some people use a Antek toroïdal power transformer and hide it in a car wax can for the look ... Those transformers are very cheap and also have one or two 6,3V secondary for the heaters. Look at their PDF specs for the real output voltage with your project current needs. Shipping is only 11$ in USA for unlimited weight ...

Don't forget with a two diodes fullwave rectifier with capacitor input, IDC = IAC but with a bridge, IDC = 0,62 x IAC ... Also, the deep bass often need much more current than the medium frequency and it is better to choice an oversize transformer.

Alain. :)


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