Can power supplies/adapters be used to clean up dirty generator power?

[artis]

We had a 3-phase 208 to 480 motor-generator in our electrical room at a previous campus, because of all of the powerline testing we did. It was about a cubic meter in size, and surprisingly quiet (until it got close to its PM interval). I don't recall the power transfer capability...

Please do not ask me how I know this...

Can I instead now ask you how you don't know this?

 

[DaveE]

We had a 3-phase 208 to 480 motor-generator in our electrical room at a previous campus, because of all of the powerline testing we did. It was about a cubic meter in size, and surprisingly quiet (until it got close to its PM interval). I don't recall the power transfer capability...

We had a 120/208V, 60Hz to 120/208V, 50Hz motor generator in our electrical room for product development. About 40KVA, which was unfortunate because we really needed 50-60KVA for worst case. There's rumors that some EEs would overload it for a while to get their data (of course I wouldn't know ANYTHING about that). Most companies don't need a big 50Hz source, but for us it was important since we designed linear DC power supplies up to about 50KW. 50Hz vs. 60Hz is a big difference for a 50KW rectifier.

 

[AmericaN8]

Just a little update for the heck of it, using a handheld o-scope the wave form is still pretty dirty. Looks more like a sawtooth than it does a sine wave.

 

[CW2]

Interesting thread here. I think Steven's question is valid and some of the replies were not great and some were just uncalled for. I have nearly the same question as Steven which is why I am here.

A standard electric generator will produce 10 to 15% of Total Harmonic Distortion. Mine is closer to the 15% range. I was primarily using it to power the furnace, refrigerator, and some lights. The manufacturer of the generator does not recommend using any electronics with this generator. The IEEE std 519-2014 states the THD needs to be less than 5% for electronics so clearly I am not in that range. (In comparison, an Inverter generator has a rating of 3% or less so they are safe for electronics).

As I understand it, Stevens question was if a laptop power supply would filter the THD so it could be used with a standard generator. I have the same question. It seems like it will but maybe a high end large screen TV maybe not so much. I have my modem, router and NAS connected to a APC BE650G1 650 VA UPS. If I connect the TV to this UPS will it allow their use with 15% THD coming into the UPS?

 

[rbelli1]

Well, technically, we only had to evacuate the building once and call the Fire Department.

It's funny how you can find a companies best and worst employees by how many times they had to call the fire department.

BoB

 

[Tom.G]

I have my modem, router and NAS connected to a APC BE650G1 650 VA UPS. If I connect the TV to this UPS will it allow their use with 15% THD coming into the UPS?

In normal operation, these small back up systems do a little filtering and just feed the incoming AC to the output sockets. When the incoming power disappears, they switch to the battery-powered inverter. So in normal operation the won't help much, if any. There are (larger) models that operate continuously so the output is always relatively clean, and no switch-over transient. (more $$$ though)

You would be better off buying a Constant-Voltage sine wave transformer, the low power ones are available from 30W thru 7,500W, but they are not cheap.

I actually had to do this for a computer installation back around 1976. It was a business (a service bureau) that had an Open House introducing their new services.

It also happened to be the first warm Spring day. The power line voltage sagged when everyones air conditioner came on. Oops! Between the voltage sag and a marginal computer power supply, the "New" computer wouldn't even boot-up. Two days later the whole system was on a Constant-Voltage (CV) transformer.

Everyone was (mostly) happy.

Here is a datasheet link to one of the major US suppliers of Constant-Voltage (CV) transformers:
https://www.appleton.emerson.com/do...usoidal-transformers-solahd-en-us-7438572.pdf

You MAY be able to find an industrial grade Line Conditioner or Line Filter that would be adequate for a lower cost. Hopefully someone else here has better information/sources for those.

Cheers,
Tom

p.s. Historically, one of the main reasons device manufacturers don't recommend electronics usage with a generator is that some generators are/were prone to voltage spikes on their output lines. Then the consumer complains about a short lifetime and wants a warranty replacement of the electronic device.

 

[artis]

A standard electric generator will produce 10 to 15% of Total Harmonic Distortion.

I think one would also need to specify the generator type as those values then might vary. Are you talking about a diesel driven synchronous generator?
And even for a single type generator I think the output distortion is partly related to the pole count , size , and winding pattern of the generator.
Someone more knowledgeable in generators could correct me , but I would think large power generators produce less of said distortion.
@anorlunda ?

 

[anorlunda]

Someone more knowledgeable in generators could correct me , but I would think large power generators produce less of said distortion.
@anorlunda ?

Sorry, but portable generators are not my field. The grid delivers low harmonics in most cases, and traditionally most generators on the grid are synchronous. But solar and wind bring other types of generators and they manage low harmonic content. Also, with the grid there are many other sources other than the generators for THD creation and THD filtering.

But the main reason grid power is very clean is that power quality standards including THD are mandated by the regulations. Sources of harmonics must be tracked down and either eliminated or filtered. In other words, the solution for big problems is to spend big money.

My source https://cdn2.hubspot.net/hubfs/446633/White_Papers/WP273.pdf
claims that his testing shows that inverter type portable generators delivered the lowest THD. For alternator type portable generators, he blames the automatic voltage regulators, AVR, for harmonic creation.

 

[CW2]

Interesting thread here. I think Steven's question is valid and some of the replies were not great and some were just uncalled for. I have nearly the same question as Steven which is why I am here. I believe the question really relates to

In normal operation, these small back up systems do a little filtering and just feed the incoming AC to the output sockets. When the incoming power disappears, they switch to the battery-powered inverter. So in normal operation the won't help much, if any. There are (larger) models that operate continuously so the output is always relatively clean, and no switch-over transient. (more $$$ though)

You would be better off buying a Constant-Voltage sine wave transformer, the low power ones are available from 30W thru 7,500W, but they are not cheap.

I actually had to do this for a computer installation back around 1976. It was a business (a service bureau) that had an Open House introducing their new services.

It also happened to be the first warm Spring day. The power line voltage sagged when everyones air conditioner came on. Oops! Between the voltage sag and a marginal computer power supply, the "New" computer wouldn't even boot-up. Two days later the whole system was on a Constant-Voltage (CV) transformer.

Everyone was (mostly) happy.

Here is a datasheet link to one of the major US suppliers of Constant-Voltage (CV) transformers:
https://www.appleton.emerson.com/do...usoidal-transformers-solahd-en-us-7438572.pdf

You MAY be able to find an industrial grade Line Conditioner or Line Filter that would be adequate for a lower cost. Hopefully someone else here has better information/sources for those.

Cheers,
Tom

p.s. Historically, one of the main reasons device manufacturers don't recommend electronics usage with a generator is that some generators are/were prone to voltage spikes on their output lines. Then the consumer complains about a short lifetime and wants a warranty replacement of the electronic device.

Thank you for the great reply. I had looked at Online double conversion UPS's but I would need 2 and that would cost more than if I just went out and purchased a new inverter generator to supply just my electronics, leaving my old generator to supply the house. I have never tried using my electronic devices with the old generator because of the warning from the generator manufacturer. Am I being overly cautious? Could the THD damage my devices, or as Steven had asked when starting this thread, will the power supply for a laptop computer filter out the THD noise. The TV is probably a different story since there is no power conversion coming in. Thanks

 

[CW2]

Sorry, but portable generators are not my field. The grid delivers low harmonics in most cases, and traditionally most generators on the grid are synchronous. But solar and wind bring other types of generators and they manage low harmonic content. Also, with the grid there are many other sources other than the generators for THD creation and THD filtering.

But the main reason grid power is very clean is that power quality standards including THD are mandated by the regulations. Sources of harmonics must be tracked down and either eliminated or filtered. In other words, the solution for big problems is to spend big money.

My source https://cdn2.hubspot.net/hubfs/446633/White_Papers/WP273.pdf
claims that his testing shows that inverter type portable generators delivered the lowest THD. For alternator type portable generators, he blames the automatic voltage regulators, AVR, for harmonic creation.

Yes, an inverter generator would take care of the problem as they are usually in the 3% THD range. Also, most permanent home generators have circuitry to keep the THD to around 5%. The problem comes in with standard portable generator that can produce 10 to 30% THD depending upon the supplier and the quality of the unit. As I understand it, the industry has established no more than 5% THD for electronics. So the problem then is those generators that produce 15 to 20% THD.

 

[mcblatz]

What if I am plugged into a battery backup/surge protector? Will this clean up the frequency.

 

[berkeman]

Welcome to PF.

What if I am plugged into a battery backup/surge protector? Will this clean up the frequency.

A UPS unit will contain an inverter to convert the DC battery power to AC Mains power. The harmonic distortion (THD) rating will depend on the specs of the inverter. It's not a matter of cleaning up the 50/60 Hz frequency, it's a matter of how "clean" the AC Mains sine wave is (since it's being generated with switching magnetic circuits).

https://en.wikipedia.org/wiki/Power_inverter