Generally speaking, what happens when draw exceeds capacity?
In this case, i would like to connect a 12v 18w water pump to a pc motherboard fan header which (presumably) is rated for 1amp (an industry standard from what i understand)..
At 12v and 18w, the draw from the pump is 1.5amp (watts=volts * amps), which exceds the asumed capacity of the header by 50%.
I understand that the pump cant draw more than what is offered by the header, but what, if any, risk is there of drawing at 100% on the motherboard. Conversly, what is the affect of under supplying the pump?
The fan header is able to run in either pwm or dc mode for controlling fan speed (or, pump speed in my case). Obviously, i will be setting it to DC mode, which reduces the voltage as a means of controling the pump anyways. (there's a clue...)
Still, i wont be able to get it to 100% capacity at a minimum.
As a potential solution, is there some sort of "variable" voltage relay i can use?
Many thanks for your kind consideration. As a curciutry-newb, any sound information is golden.