[Amps] Series PC Power Supplies

[Will Matney]

Jim,

Yes, the load most certainly can draw more current because of a voltage drop if it's producing the same power output. If the load takes say 12 volts at 10 amps for 120 watts, and the voltage drops for some reason to say 10 volts but the load still consumes 120 watts, the current will then be 12 amps. This can happen in an amp say if the voltage drop was to drop the power out and the drive is turned up, etc to raise it back up to the original output power. What if the equipment has an AGC to monitor the output power, and with a drop in input voltage, the AGC increases the gain, etc to maintain the power, the current being drawn will increase. It has to as you can't get the same amount of power out with the lesser voltage and same current. There's one law that will always be there, for any current drop you will have a voltage rise, and for any voltage drop you will get a current rise in any circuit. If one put their mind to it, they could think of thousands of different items and applications where this would apply. If it wasn't a problem, we wouldn't need a constant voltage power supply. In other words, as more current is required from the supply, the resulting voltage drop causes the regulator to adjust and hold a constant voltage to the load. If say one of three supplies failed in the cascade, there would be a 1/3 voltage drop and a 1/3 current rise if the load was producing the same output.

Best,

Will


*********** REPLY SEPARATOR  ***********

On 6/1/06 at 9:57 PM Jim Forsyth wrote:

>So you are saying when the voltage drops the load draws more current.
>What 
>kind of load is that and what is the application?
>
>Jim, AF6O
>
>
>> Jim,
>>
>> I think what he's getting at is this. The power supplies to be seriesed 
>> are calculated to provide a certain set operating voltage at a certain
>set 
>> current. Together these seriesed supplies total the amount needed. The 
>> load requires this set amount of voltage and current to operate
>properly. 
>> Ok, if one supply fails in the string, there is a voltage drop. This 
>> voltage drop creates a current rise from the remaining supplies feeding 
>> the same load. 
>
>
>
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