Effect of low power factor on Computers

[chaterpilar]

Season's Greetings,


In one of the company the IT guy brought in a power quality expert and who claimed that all computers should be fed with 0.95 power factor power supply or the computers can fail. Our pf is 0.85.

The problem we are facing is particularly related to power supply of the computer and the hard discs failure. This computer has 8 USB ports and each port is connected to 25 flowmeters for networking via USB to CAN device.

I am suspecting that there is some nuisance voltage coming to PC through this USB port. Is there any device which can be put at the USB port to save the PC from this voltage?

All flowmeters are 24 vdc, and any leakage can cause the DC voltage to creep into the PC.

Is there any way to check this leakage?

Has anybody faced such power related probems causing computer failures?

All ideas appreciated.

Cheers.

 

[LarryFine]

I didn't know that sources even had power factors.

 

[dbuckley]

The humble PC has a switched mode power supply, and these are completely unfussy about what you feed them with, sine wave power, square wave, DC, they just dont care, as the first thing they do is to rectify the incvoming mains to DC...

 

[StephenSDH]

For your PCs you should only be looking at voltage distortions. Sags/Swells/Voltage Harmonics

 

[Besoeker]

Season's Greetings,


In one of the company the IT guy brought in a power quality expert and who claimed that all computers should be fed with 0.95 power factor power supply or the computers can fail. Our pf is 0.85.

All ideas appreciated.

Cheers.

Your Yuletide felicitations are reciprocated!

Power factor is a function of load, not supply.
Ideas? Re-define your expectations for "power quality expert".

 

[StephenSDH]

The problem we are facing is particularly related to power supply of the computer and the hard discs failure. This computer has 8 USB ports and each port is connected to 25 flowmeters for networking via USB to CAN device.

Maybe you are exceeding the Wattage ratting of the USB supply having 8 devices plugged in?

It could also have to do will grounding. Grounding on communications is critical. I have seen communications boards fail from ground loop currents, grounding at 2 locations. You might want to use Canbus signal isolators, or a USB Isolator to protect the computer.

 

[brian john]

What I would do Hire an expert, that did more than buy a meter and claim to be an expert.

I have seen more of this lately as contractors trying to maintain work have bought some of the newer Flukes (prices have fallen drastically with newer monitors).

Then I would check with the manufacture for a recall of their products and/or a history of failures, better than 75% of the PQ issues I look at are actually hardware issues. Also question the EXPERTISE of the IT tech, I truly believe in tech school they recite the phrase daily, "your electricity is dirty" and you have a dirty ground".

Then I would verify you have no electrical issues with your facility

Infrared, grounding investigation and monitor the voltage for the noted sags, swells and you can check for harmonics but do not be freaked out when you find out you have harmonics..

 

[chaterpilar]

Updates

Updates

Thanks everybody for the inputs...no failure since last three weeks. Checked the USB load it is 0.8 watts. It is well within the capacity of PC.



Yes PF is function of load...but for a particular load the powermeter records a pf and that is the system pf.( i misnomered it as supply pf).

This system has a online APC UPS connected which should help with sags and swells.

Cheers.

 

[ELA]

last O.P. response changed my opinion so delete me.

 

[ohmhead]

Well try this http://www.epcos.com/inf/20/50/ds/B44066R3333E230.pdf


Before they had USB ports that everthing in the world can plug into today and one can overload by adding many other devices we had the old serial port which was not easy to overload .

But there is one old time correction its two resistors and a npn transistor kinda a digital switching circuit thats whats in that box they call a power factor correction device .

There are other options but your IT tech should know ?

 

[ohmhead]

Well heres one more read this its more detailed http://www.eedigest.com/ecn/Renesas...Series-Power-Factor-Correction-Control-ICs/:D

 

[steve66]

If you are reading 25 flowmeters and storing the data on the hard drive, are you sure you aren't just overworking the hard drive?? It sounds like it might be running 24x7.

Steve

 

[gar]

091221-0956 EST

Starting with the first post.

In one of the company the IT guy brought in a power quality expert and who claimed that all computers should be fed with 0.95 power factor power supply or the computers can fail. Our pf is 0.85.

This is total nonsense as has be pointed out.

The problem we are facing is particularly related to power supply of the computer and the hard discs failure. This computer has 8 USB ports and each port is connected to 25 flowmeters for networking via USB to CAN device.

Is the only problem hard disk failures? If nothing else fails, then look for heat, dust (sand), and mechanical reasons. What is failing on the disk? Is it simply data corruption and reformatting corrects the problem? If so, could be the drive or external to the drive. If it can not be reformatted, then is it the drive electronics, or internal to the enclosed drive mechanism?

You may need to consider data noise from your USB channels, unless there is electrical isolation of the ground path.

I am suspecting that there is some nuisance voltage coming to PC through this USB port. Is there any device which can be put at the USB port to save the PC from this voltage?

Your "nuisance voltage" might cause data errors, but there are a lot of easily damaged components between the USB connector and the hard disk so if there is outright damage to components in the hard disk, then there should be others in the path. There are isolators for USB. See
http://www.icsdatacom.com/pdfs/USB-GT_ds.pdf

As mentioned in another post you might be excessively overworking the mechanical parts of the drives by an excessive number of write cycles. Are there large RAM buffers for the data so that hard disk writes are minimized?

.

 

[mivey]

Ideas? Re-define your expectations for "power quality expert".

LOL . :grin:

 

[Smart $]

...

All flowmeters are 24 vdc, and any leakage can cause the DC voltage to creep into the PC.

...

Thanks everybody for the inputs...no failure since last three weeks. Checked the USB load it is 0.8 watts. It is well within the capacity of PC.

...

Perhaps I'm missing something here... but USB port (at least your standard 1.x, 2.0) power terminals are Ground and +5vdc. Are you sure you are powering 24vdc devices???

 

[chaterpilar]

Update

Update

Perhaps I'm missing something here... but USB port (at least your standard 1.x, 2.0) power terminals are Ground and +5vdc. Are you sure you are powering 24vdc devices???

USB port is not powering any field devices.. it is collecting data from the field.

To answer other posts...the hard discs and power supply units inside the PC are have no signs of burnout.

The Hard disc is not in use continuously ( the Green LEd ) comes in say once in two to three minutes.

 

[Smart $]

USB port is not powering any field devices.. it is collecting data from the field.

OK... had to make sure, because your posts made it sound otherwise.

To answer other posts...the hard discs and power supply units inside the PC are have no signs of burnout.

Of the ones I had fail, you could not tell by visual inspection.

The Hard disc is not in use continuously ( the Green LEd ) comes in say once in two to three minutes.

Typically your hard drives run continuously, whether they are being read from, written to, or neither. You can change how long the hard drives run without a read or write in advanced power options on a Windows machine... but stopping and restarting your hard drives continuously can be more detrimental than leaving them run continuously. That said, not all hard drives are built for 24/7 operation.

Do you have any monitoring software on the system... something like Speedfan, perhaps...???

 

[gar]

091222-0819 EST

In what manner have the hard drives failed? How do you know that the drive failed? There may be a software bug that has destroyed data on the drive. This might even be a Microsoft caused problem.

.