PC Power supply question...

[J Shrum]

I've been using a 250W PC power supply as a bench supply.
Question:
The ratings are on the label stating 12V - 7.5A surge.
So if 7.5A is the absolute max, what would I expect the RMS to be? I'm
running it into a flyback w/ a primary resistance of like 1ohm... I assume
I'll have to throw a high wattage resistor in there to bring down the
current through the primary, but what is the most that I can *safely* draw
from this supply @ 12v.

Thanks...

Jim
KC9FFX

 

[Tom Biasi]

"J Shrum" <shrumj@spam.is.evil.madisontelco.com> wrote in message
news:GqqdnTJop_vJLqXfRVn-sw@madisontelco.com...

I've been using a 250W PC power supply as a bench supply.
Question:
The ratings are on the label stating 12V - 7.5A surge.
So if 7.5A is the absolute max, what would I expect the RMS to be? I'm
running it into a flyback w/ a primary resistance of like 1ohm... I assume
I'll have to throw a high wattage resistor in there to bring down the
current through the primary, but what is the most that I can *safely* draw
from this supply @ 12v.

Thanks...

Jim
KC9FFX

Hi Jim,
Usually the PS units have a maximum rating and a rating for each supply
voltage.
I haven't seen a 'surge' rating on a PC supply only a maximum output.
Since you are using only the 12 V. section you would need to respect the
rating for that section.
If indeed your unit specs a surge then the continuous will be less than
that.
Since 12 V. with a 1 ohm load draws 12 Amps continuous, I think that we can
*safely* say you are exceeding the limits of the PS
A 7.5 A. surge could be 5A continuous or less.
Regards,
Tom