PC turns off immediately after UPS switches from Battery backup to AC mains

Subhajitdas298 · May 12, 2015

PC turns off after UPS switches from Battery backup to AC mains.

UPS: MicroTek MDP800+ (Dual battery 800VA)
Mains voltage (Rated): 230V
Mains voltage (Practical): 200V - 150V

What can be the problem? Need help immediately. Can not use my PC for long.

reedo_43 · May 12, 2015

Why is it switching from battery backup? Are you losing power?

InvalidError · May 12, 2015

If it were me, I would pull the cover from the breaker box or service disconnect switch and measure voltage coming in directly from the utility meter to rule out loose connections downstream from there.

If you are in a 230V country and only get 150-200V, then it seems the logical thing to do would be filing a complaint with the power company for grossly unstable line voltage and hope it will do something about it.

Your other option would be to buy a line voltage regulator with adequate input range capability or possibly a double-conversion ("online") UPS that can accept low input voltage.

ko888 · May 12, 2015

Most likely because the PSU's hold-up time is too short not allowing enough time for the PSU to remain powered while the UPS switches back to AC mains power.

Subhajitdas298 · May 12, 2015

reedo_43 :

UPS switches to battery backup when mains power cuts off or Low voltage (around 150V-160V).
But no problem here.

Problem occurs when AC mains gets back, and UPS switches from battery backup mode to AC mains again.

Subhajitdas298 · May 12, 2015

ko888 :

How to solve it?

reedo_43 · May 12, 2015

Get an electrician to fix it properly.

Subhajitdas298 · May 12, 2015

reedo_43 :

How an electrician can help, fixing this?

InvalidError · May 12, 2015

Subhajitdas298 :

By finding out why your line voltage is dropping so far below 230V and hopefully getting the power company to fix it if it is on their side of the service disconnect switch so your line voltage no longer dips that low.

Tolerances on line voltage are usually 10% not counting surges, swells, dips, brownouts, etc., so 200V "practical" should not be normal..

Subhajitdas298 · May 12, 2015

InvalidError :

Ya, I reported my Problem many times to my power company, as this low voltage problem is not explicitly for me. This is the problem of our locality.
The government operated company (WBSEDCL) dosen't care for it.
As in India, nothing government based systems can not be good (being perfect is imaginary). Whereas private supply company CESC provides supply of 230V to 240V.

InvalidError · May 12, 2015

Your best option would be trying to get something like this:
http://www.tsipower.com/uploads/product-documentation/VRp-3000-5000-02xx-230V-2008-05-15-UK.pdf
230V +/- 3% from 172-276V input.

But even that option may still require an auto-transformer in front to boost your worst-case 150V up to 175V first.

Subhajitdas298 · May 12, 2015

InvalidError :

But my problem isn't the low voltage here. Is it?
My computer can directly run from an 150V outlet directly, but problem occurs with UPS, when switches back.

InvalidError · May 12, 2015

Subhajitdas298 :

As mentioned earlier, the problem might be that your PSU does not have enough hold-up capacity to stay up when it gets switched from UPS to low line voltage.

Another thing you could consider doing is getting a better quality power supply but those appear to be a rare and expensive sight in India based on past posts by Indian members.

Subhajitdas298 · May 12, 2015

InvalidError :

I am currently using VS550 and considering CX650 or RM650 or Seasonic 620 watt PSU in future when I will upgrade my PC for GTX 970.
But if necessary I will go now. But have to make sure, it will work. How can I do so?

makkem · May 12, 2015

Hi
What PSU do you have in your computer ?
It seems to me that the capacitors in the PSU are not keeping the supply voltages up long enough to cover the time it takes the UPS to switch which a good PSU would do.

Subhajitdas298 · May 12, 2015

makkem :

Corsair VS 550

makkem · May 12, 2015

Thats a tier 3 PSU which is ok but not too good and may well have Taiwanese capacitors which are not as good as Japanese ones.
It would probably be worthwhile upgrading the PSU.
However if it is a fault in the UPS causing slow switching then a new PSU may not help.
Can you detect any delay as the UPS switches ?
It will be easier to check this by unplugging everything from the UPS and plugging in a single light bulb then unplug the UPS from the wall and plug it back in again to simulate a power cut.
If the light bulb goes off completely before coming back on then it may be a problem with the UPS if it only flickers then the UPS will be OK.

ko888 · May 12, 2015

ATX12V Power Supply Design Guide Minimum Allowed Hold-Up Time: 16.0 ms

Corsair CX600/CX600M: 6.8 ms
Corsair CS650M: 11.6 ms
Corsair RM650: 12.8 ms

Those three models don't even meet ATX12V specs.

Hold-Up time is not the only thing you need to worry about when upgrading the PSU. You also need to determine if the new PSU's APFC (Active Power Factor Correction) circuit will be compatible with the UPS it will be plugged into.

Subhajitdas298 · May 13, 2015

ko888 :

Where did you find the hold times?

InvalidError · May 13, 2015

Subhajitdas298 :

In power supply reviews. ATX PSUs are presumed to follow the ATX spec and most manufacturers do not bother specifying it, so the only place where you are likely to get numbers for it is PSU reviews.

Hold-up times are based on the assumption the PSU had a long enough pulse of sufficient amplitude to charge the input cap to their nominal voltage before power gets pulled though.

Since your PSU has active PFC, it is also possible the PFC circuit is getting confused by the transition from UPS to weak AC line voltage.

ko888 · May 13, 2015

Subhajitdas298 :

Hold-up time is defined as the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations as defined by the ATX spec without input power. Another way of saying it is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption event.

Corsair CS650M, CX600M and RM650 can be seen here:

Hold-up times that are too low are a result of using APFC capacitors that are too low in capacitance value. This is usually the case with budget level PSU's because lower capacitance value capacitors cost less and shaving cost is the primary concern.

Subhajitdas298 · May 13, 2015

InvalidError :

I just bought an AC Voltage Stabilizer, but same problem remains.
The voltage is now 210v to 220 v, which is good.

Subhajitdas298 · May 13, 2015

ko888 :

Subhajitdas298 :

Hold-up time is defined as the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations as defined by the ATX spec without input power. Another way of saying it is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption event.

Corsair CS650M, CX600M and RM650 can be seen here:

Hold-up times that are too low are a result of using APFC capacitors that are too low in capacitance value. This is usually the case with budget level PSU's because lower capacitance value capacitors cost less and shaving cost is the primary concern.

This information is good but, practical hold up varies with load, isn't it?
Any way suggest me where to find the listing of this.

ko888 · May 13, 2015

Subhajitdas298 :

Yes it does vary with load. The measurement is always performed at the PSU's rated maximum power.

Most power supply review sites don't even measure hold-up time.

The graph I posted is from here: http://www.techpowerup.com/reviews/Corsair/CS650M/5.html

Subhajitdas298 · May 13, 2015

ko888 :

Can you provide Hold up time for VS550 and Seasonic M12II 620

PC turns off immediately after UPS switches from Battery backup to AC mains

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