Connecting computer to 2 power sources - options?

Thread Starter

RogueRose

Joined Oct 10, 2014
375
There have been numerous times I've had to work on UPS's and I can't shut down the system. Is it possible to put a switch in line with the power input so I can switch the power over to a different source say from the UPS to the wall (or other UPS)? Would the caps in the UPS function for the few ms it takes to switch over?

I was thinking another option would be to add a larger cap in the power supply after the rectifier I guess. I would think this might give enough cushion for a switch to work.

Anyone have any thoughts?
 

Thread Starter

RogueRose

Joined Oct 10, 2014
375
It was as simple as Googling for "move computer without losing power".
http://www.cru-inc.com/products/wiebetech/hotplug_field_kit_product/
Thanks! So can I have your credit card # for the $600? Is adding a larger cap after the rectifier not an option? I could see that it might not fully charge or have difficulty charging depending on how large it is but my PSU is 750w but the machine only uses about 180 on average and the PSU has already been opened up and it would be easy to add a cap inline with the current one.
 

dl324

Joined Mar 30, 2015
14,308
180 on average and the PSU has already been opened up and it would be easy to add a cap inline with the current one.
Should just ignore you but I was actually taking your request seriously and trying to be helpful....

If my calculations are correct, 80,000uF would give you about 5 seconds with a 200W load.
 

Thread Starter

RogueRose

Joined Oct 10, 2014
375
Thank you for your reply. I'm sorry if that came across more harsh than it was intended. I really can't afford something of that magnitude for the application but if there is a more economical fix, then I'd give it a try.

What I'm wondering is since there is a 820uf - 400v cap after the rectifier, I was wondering if putting in a triple pole double throw (3PDT) switch that is connected to the wall and the battery backup - so if I want to work on the UPS I can switch to the wall outlet with the switch. I would think that the amount of time it takes for the switch to function is pretty low and I would think faster than 1/20th of a second which, by your calculations, is about what the 820uf cap would provide if 80,000uf provides 5 seconds. If these things are correct then I need to figure out how fast switches work and how much difference there is between different types of switches. I'm guessing there are some that are much faster than others when dealing with manual switches.
 

Ramussons

Joined May 3, 2013
1,228
There have been numerous times I've had to work on UPS's and I can't shut down the system. Is it possible to put a switch in line with the power input so I can switch the power over to a different source say from the UPS to the wall (or other UPS)? Would the caps in the UPS function for the few ms it takes to switch over?

I was thinking another option would be to add a larger cap in the power supply after the rectifier I guess. I would think this might give enough cushion for a switch to work.

Anyone have any thoughts?
Why not Try it out. Normally, a few milliseconds of AC power loss normally does no harm.

I had no problem (till recently) with my Offline UPS coming Online even with a DVD writing in progress.
I started having a problem when I changed my motherboard; the PC would Switch Off (not shut down) when the switch over took place.
I doubled my Post Rectifier Capacitors and solved the problem.
BUT when I tripled it (just for a study), the input fuses blew... and continued to do so.
So I'm back to Double Value Capacitors and doing fine.

Just for info.
 

LesJones

Joined Jan 8, 2017
3,701
If this is just for your own use and the load is only a switch mode power supply in the computer that would work just as well on about 300 volts DC as it does on 240 volts DC then You could rectify both the UPS output and the normal mains and feed the DC from each source via a diode. You would have to be sure that the UPS output was floating. If it was not then the normal mains would need to be fed via an isolating transformer. I would not advise putting an isolating transformer on the UPS output due to the non sinusoidal waveform.

Les.
 
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