Part Rating descrepency

Nov 06, 2007 2 Replies
M

I'm the second owner of an HP computer, it has a "Classic Power" brand power supply Model JPS3-300. I wonder if this is an OEM power supply? The power supply started smelling hot yesterday, after dissassembly I found as I touched the blackened inrush limiter it fell apart. The part is a NTC 5D-11, it is rated at 3.3 amps. See

formatting link
The power supply input is listed as 115/230Vac 10/5A 60/50Hz. I'm using



115 Volts so the max input current could be
10 amps, even if we say 1/2 or 5 amps this is still more than the rating of this device. What do you think? What am I missing? Mike

Vote
Twitter Facebook LinkedIn
N

The distinction between continuous current and surge current.

110V * 10A = 1100W, which is rather high for a computer PSU. A more typical figure is 300W, which corresponds to ~2.7A @ 110V. 3.3A would give you 363W.

I'd guess that the 10A/5A figure corresponds to the absolute maximum peak current. Thermistors are rated according to their continuous current, along with a variety of other parameters which determine their ability to handle inrush surges (this isn't something that can simply be assigned a number as can be done for the continuous current).

In all probability, something inside the PSU failed short-circuit, causing the thermistor to pass excess current for more than just a brief surge. Apart from limiting the inrush current, a thermistor will also double as a fuse; this appears to be what happened here.

Vote
Twitter Facebook LinkedIn
M

Hi nobody, I appreciate the response, I should have crunched those numbers, your right 1100W makes no sense. The computer was working fine when I shut it down, it just started smelling. The inrush limiter must have been just making a connection because when I touched it, it fell into three or four pieces. I'm hoping it was just a run away situation and that is the only defective part. I have one on order. Thanks, Mike

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required