It might be happening to you that whenever power fails, your computer either restarts or shutdown completely even though you have connected UPS (uninterruptible power supply) or Power Inverter to it. It is a weird situation that UPS totally fails to perform its duty. The problem can be fixed but it requires technical help from an expert. Here, I have discussed in general why it happens and how to resolve the problem.
The major reason behind this problem is that switch over time of UPS is longer than the threshold of power supply of computer. Mostly, good computer power supplies have threshold of almost 15-20 milliseconds which is generated by capacitors inside them. Any interruption of electricity longer than the specified duration can restart or shutdown the computer.
If you are using a good quality expensive power supply then issue is solely related to the relay of UPS. Relay is a device which is responsible for switching over from external power source to backup battery power. Poor quality mechanical relays have longer switch over time. So, the problems arises.
The cheaper modified (simulated) sine wave power inverters that are designed to run with large or small external batteries often cause this problem. Poor relays in them cause longer switch over time from main power source to batteries backup.
In majority cases, problem is solely related to UPS or Power Inverter. Several UPS manufacturers now use solid state relays instead of mechanical relays to fix this issue. Solid state relays are extremely efficient and offer lowest possible switch over time.
If problem is actually related to the relay of UPS as discussed above, it can be fixed by replacing the relay with a better quality mechanical relay or solid state relay. On the other hand, if the problem is related to the capacitors of PSU, the problem can be resolved by installing larger capacitors. These are the technical works and can only be done by experts.
Since, an ordinary user who has no knowledge of electronic circuits can not fix the problem by himself. The best way to overcome the situation is by buying a new better quality UPS or Power Inverter. Make sure to confirm from seller that it is really designed for computers and will not cause troubles. Obviously, it is an expensive solution but quite hassle free.
The other easy fix is change PSU of computer. But this might not work in all cases. Changing UPS (or Power Inverter) is the only reliable and money saving solution as discussed above.
Thank you for this very educational article. My question was already answered. I do have 1 more question, is it safe to plug in my internet to the UPS? ( I just read on my UPS manual that only computers should be plugged on the UPS)
You can plug anything as long as it doesn’t overload UPS.
My ups work very well when there is a power supply to it
but when the power supply to the UPS is off
the ups will just be doing OFF and ON, Off and On Continuesly within each seconds
for a long period of time
please what could be the problem and the solution to it
Good Article man…Now i know what is happening between my UPS and CPU when power goes off…Thank you for sharing your knowledge..
It was an informative article, much appreciated. However, I’m facing a unique issue. My Intex 725 Protector UPS takes over when the light is gone without any problem, but when the light comes back, its alarm sounds off and my computer restarts. I was facing the same problem with another UPS (iBall Nirantar). What is happening with the UPS? Please help. Thanks in advance.
Run it without connecting any load and see if it gives same error. Then run it after connecting small load like may be bulb and see how it behaves. If problems persists you should take it to service center to get it fixed.
Can anybody tell me how to turn on UPS mode on Luminous eco watt invertor.
when there is main power available, bulbs do not light up. But when power fails these start lighting up. Please mention solution.
Check the wiring. Make sure input and output are properly aligned if only live wire has been supplied to bulbs from UPS.
See this post for more details: http://benignblog.com/2011/05/how-to-circuit-ups-with-house-wiring.html
My computer randomly restarts during fluctuation and power cuts. I don’t have a UPS but my pc’s wall socket does have Inverter Connection. I started having this problem after i cleaned my PC dust through a leaf blower. I feel i likely damaged my motherboard but i also have doubts about my PSU.
i am having problem with my ups.it is restarting on all sunday and the battery graph will be low.after it restarts will works for whole week untill next sunday.i feel it as a mystery.can you help me to figure it out?
check the input voltage on that day. Disconnect output and run it isolated to test it.
Thanks for your reply.
but we are using 3 ups in that floor but only one keep restarting
Run it without connecting output and check. If it does the same then get it repaired.
Updated article. Added some new details.
Originally posted on Jan 22, 2012
I am also having same issue, swapped the UPS also to check but issue is still present, the computer restarts. I am using Intex PSU. checked with using APC, Intex and Zebronics UPS. No one is fail proof.
What specifications to look for in a good PSU which will ensure that it holds on till the UPS kicks in and doesnt restart the computer while switching to UPS.
Look for a good quality PSU like cooler master, thermaltake, thermal master or similar other brands
Can I operate pc ups wih home ups Power supply..bcs. Both ups flow to DC Power supply
when i do not connect my pc with UPS. The pc doesnt get restart at random point. Its only with when i connect my UPS. do you think its something to do with an UPS>?
Hey talal thank you i was looking for this kind of a topic.
My problem is even tho ac power is on and everything working fine. My ups make a short noise (like switching) and my pc gets restarted. this is not happening when power cuts off.
i ball ups of 1kv
corsair vs 650 smps
Check the voltage of mains. It could be low which is causing abrupt switching.
My inverter shuts off the output voltage when its online, and you switch on the inverter.what could be the possible cause, I will appreciate your lovely kind gesture of a reply
Is it running fine on backup mode? It should keep supplying electricity when main power is available.
I have NS super 5 inverter and it is giving low output voltage on battery mode. please give me solution of this problem.
Put the load on inverter and check again if voltage rises.
Hello Talal, thank you for your interesting blog. This really sounds like a solution to my problem with my UPS in my office. I have four computers connected to a UPS. But sometimes in case of power failure one or two or all computers shut off or reboot, when I deliberatly switch off the power supply, though, the computers do not reboot. We have recently changed the ups, because the old one caused problems too and the batteries were dead. First the new ups worked for a month or so but now we have this new problem. You suggest that the cause of the problem is the PSU in the computers…what do you think we can do to have a relaible power supply for our computers. Thank you so much for your help. Kind regard
I have 3 computers connected to my UPS. Only one computer reboots. I got the relays replaced, the batteries changed but the problem persists. Another curious fact is that if I deliberatly switch off the power supply, the computer does not reboot. It is only when I shut off the mains or in case of power failure, this computer reboots. What seems to be the problem?
Thanks in advance.
You shouldn’t have changed the batteries if those were giving good backup and only one computer was making trouble. It is obviously an issue related to the power supply unit of that computer which you can fix by buying and installing a new good quality PSU.
The reason why computer restarts when power failure (or loadshedding) from grid station occurs and doesn’t restart when you yourself cut off the electricity supply is that when power fails from the grid, the voltage does not drop to 0 abruptly. Current still keeps flowing in the wires with enough voltage not allowing UPS to switch over to backup mode, but not enough for the computer to keep up functioning normal. So, the computer restarts due to the drop of voltage for the milli seconds exceeding the threshold limit of PSU.
If you are using inverter type UPS, these have a small switch on them from where you can choose between Narrow Range and Wide Range of voltage. Always choose the Narrow Range mode to make inverter act like a UPS.
We also facing same problem.
turned out it was the problem of my PSU…. replaced it … everything is fine now…
Which PSU did you buy, make/ model/ power rating ?