[Boatanchors] Power transformer

[Chuck O'Neal]

No such thing as a dumb question.

Typically, a HV secondary with a center tap is designed for a full wave
rectifier, 2 diode circuit with the center tap grounded.  Then the 300 mA
current rating is OK.  There is also another condition, capacitor or choke
input filter.  Usually with capacitor input the current rating is somewhat
less due to peak charging currents heating the transformer windings up,
although this is probably not a large effect, particularly if you are using
hollow state rectifiers instead of solid state.

With the full wave bridge, 4 diodes, then you should halve the current
rating since the voltage output will be double and for the same power, the
current will be half.  Another thing to watch out for is that the center tap
of the transformer in a full wave bridge will not be at ground potential and
may break down.  I had this happen once and when I looked up the
transformer, there was a specific warning about not doing this!

----- Original Message ----- 
From: "Joe Walden" <w5jdy at cox.net>
To: <Boatanchors at mailman.qth.net>
Sent: Thursday, December 09, 2004 2:20 PM
Subject: [Boatanchors] Power transformer


> >From Joe in Okla....  Needing assistance as always...   Question about
Power
> Transformers::   When  a Power Transformer high voltage secondary winding
> that has a center tap is rated at 300ma,does that mean if you use two
> rectifiers in a  full wave circuit and ground the center tap your output
> current will be rated at 300ma or 600ma....  What is the current rating if
> you use 4 rectifiers in a bridge circuit.   I know the voltage is doubled
in
> a bridge circuit,I also know wattage in equals wattage out with minimal
> loss... I guess the current rating for the bridge is half that of the full
> wave?? I just don't know what the current rating is in the full wave
> circuit.. and why  .. I should have learned this 40years ago??     Is this
a
> dumb question??   Joe w5jdy in Okla....
>
>
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