kenw2dtc wrote:
> Hi,
> I'm trying to figure out the current rating of a plate transformer. This is
> my test setup:
>
> http://w2dtc.com/2005-0610-transformer-test-page.htm
>
> Questions:
> 1. Is this a valid way to find the secondary current capability?
I think so. Remember that what you have measured is the rms secondary
current - which defines the heating effect. The dc current you can end
up with depends on several factors but is likely to be 30-50% of the rms
value. Best check is with the Duncan Amps PSU designer which will tell
you the rms current in the winding for different configurations,
capacitor values and load resistances, but you will have to edit the
rectifiers file to create a diode with enough PIV.
It's also worth checking how much it heats up with full primary volts
and o/c secondary, and derate the secondary current if necessary. I have
transformers that run cold like that, and others with noticeable iron loss.
> 2. Is the internal temperature of 180 degrees F too high for a transformer
> under load for 5 hours?
I'll pass on that one - if you run it at 2.9A rms but, say, 50% duty
cycle then the temperature rise will be much lower.
> 3. Is there a problem running this center tapped beast in a full wave
> capacitive input configuration?
Depends on the insulation between the centre tap and the frame. If the
designer assumed the ct was going to be ground, it might not be rated
for it. I've lost a transformer that way.
Steve
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|