Re: 12 Volt power Supply

On 22 Jun 2006 04:25:47 -0700, in message
<1150975547.206690.297970@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
indgepr@xxxxxxxxxxx scribed:

please forgive the supidity of this question but I am a mechanical
engineer and have very linited knowledge of electronics.

I have tried to biuld a 12 volt power supply for testing
motor/gearbox/pump units and the problem is that it keep blowing up

I have only a very simple circuit of a Transformer to drop the voltatge
down from 240 then feed this through a bridge rectifier ( International
Rectifier Part No. GBPC3502A ) and the connect the output via an
ammeter to the motor. once it is running it is fine, but somtimes blows
the refitier when it is turned on ( switching the AC input to the
transformer ) do I need more components in the circuit, if so what ?

The motors will draw up to 20 amps, when running the rectifier does get
hot but has a heat sink and fan from an old PC connected. but it
allways blows when you turn it on, not when it is running

I agree with what's been posted so far, that you could either beef up your
bridge diodes, or create a "soft start" circuit at the primary. But I also
notice that you haven't indicated that you have any filter capacitors as
part of your design. I wonder if some smoothing at the DC output might be
a good idea?

.

Relevant Pages

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