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LittleBill
join:2013-05-24

LittleBill

Member

switching power supply and generators

question

how "bad" does power have to be before a switching power supply cares enough to be damaged. im looking for averages

i picked up a generator a couple weeks ago, which has a beautiful sine wave under load.

that being said, i did a power test over the weekend. all my UPS's failed the test (4 of them), they would constantly keep switching between battery and power. i was annoyed to be honest

that said i googled my ups and they actually indicate they will not generally work on the generator due to the hertz needing to be within .5 htz.

my generator will range from 59 to 62 hertz depending on load.

i do not have have a inverter generator nor do i have any interest in one. i am slightly concerned about powering my 2k tv through it.

although i just realized my UPS uses MSW for its power and i have been running on them more times then i can count

so whats more important voltage or hertz, this generators holds voltage perfect and sine way is pretty damn good too.

with all these stupid electronics anymore i get slightly concerned. my electric blankets would not work, nor would some of my motion detecters for my lighting.

that said we have had generators in rvs for years and if it wasn't for the ups. you won't even see a concern. the lights don't even flicker with this generator
LittleBill

LittleBill

Member

Click for full size
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some photo's
TheMG
Premium Member
join:2007-09-04
Canada
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to LittleBill
said by LittleBill:

how "bad" does power have to be before a switching power supply cares enough to be damaged. im looking for averages

Most switchmode power supplies actually don't really care about the shape of the waveform, so long as the RMS voltage of the waveform is within an acceptable range and doesn't contain significant spikes/transients.

There are a few exceptions, notably some designs of power-factor corrected power supplies that won't operate correctly with a "modified" (stepped) wave, but these are a minority.

I find that manufacturers of UPS design them to be much too picky about the input frequency. I'm not sure why. A few hertz too high or low isn't going to damage anything. It might cause some devices that depend on the AC frequency as a timing source to run a bit slow or fast but that's about it.

We use a lot of slightly more expensive double-conversion UPS at work and none of them have problems with generator power. In fact the spec sheet for them states they will happily accept 40-70Hz.
LittleBill
join:2013-05-24

LittleBill

Member

yes i am aware of the double conversion. we use them as well. that said they are significantly more expensive, but they produce generally a perfect wave for the end device.

i don't care about the UPS. im more interested in what a switching power supply sees.

i see on alot of them 120-240 with 50-60 htz, i never see it say 55-65 htz, which makes me wonder

actually there is alot of stuff that doesn't like modified wave. microwaves/ electric blankets just to name a few.

i know the voltage ranges. i personally don't understand why a bad hertz is bad. and i've been told it can reak havok
TheMG
Premium Member
join:2007-09-04
Canada
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TheMG

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said by LittleBill:

i see on alot of them 120-240 with 50-60 htz, i never see it say 55-65 htz, which makes me wonder

That's the nominal rating. In reality, there is a margin of error with pretty much all power supplies, but is often not specified. 90-270V is not uncommon as a "safe" voltage for a power supply rated 100-240V or even 120-240V.

Same with frequency. Rated 50-60 but in reality will probably handle something like 40-70 without a problem.
said by LittleBill:

actually there is alot of stuff that doesn't like modified wave. microwaves/ electric blankets just to name a few.

Microwave ovens don't like "modified" sine waves due to the way the magnetron power supply works (either inverter or voltage doubling transformer). The electric blanket if it has an electronic control probably uses an SCR/TRIAC for switching on/off, and those don't tend to work with modified waves since they work based on phase angle switching, which can't really occur with a square/modified wave.

That being said I don't see any reason you should have any problems powering these devices from your generator.

tschmidt
MVM
join:2000-11-12
Milford, NH
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MVM

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said by LittleBill:

electric blankets just to name a few.

Since the heating element is simply a resistor I assume the problem is when the SCRs/TRACs turn on since now they are seeing a step function rather then a sine wave. That makes temperature more of a step function rather then continuous.

As far as SMPS since the AC mains get converted to DC other then subtle effects on the filter caps I would think it does not matter, other then the power factor correction circuit that try to provide unity power factor. Ought to be able to feed in the equivalent DC voltage and the supply should be happy.

Agree with you about frequency, supplies are typically rated 50/60 Hz. If the frequency is too low ripple becomes a problem, too high and ESR goes up reducing filter effectiveness and increases cap heating. Not sure why they are so finicky.

/tom
LittleBill
join:2013-05-24

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no my microwave works fine. but my motion light and my 1 electric blanket, both electronic controlled would not work while on generator power. thats kind of the whole point of the topic. i have a fairly strong understanding of electrical. just want to understand it from an electronics level, why it hates generator power so much
LittleBill

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to tschmidt
ts,

can you dumb down the second paragraph.

i want to stay focused more on the generator then the MSW inverter.

ESR? sorry alot of abbreviations i don't know yet

tschmidt
MVM
join:2000-11-12
Milford, NH
·Consolidated Com..
·Republic Wireless
·Hollis Hosting

tschmidt

MVM

Click for full size
Simplified diagram SMPS
Sorry for the technobabble.

The way a switch mode power supply (SMPS) works is to convert the incoming AC to DC. Then the the controller using a transformer and switching element creates the desired voltage. This simplified diagram ought to make it easier to understand.

ESR, equivalent series resistance - real world components exhibit lots of side effects, depending on the application in some cases they can be ignored in others need to be carefully taken into account.
»en.wikipedia.org/wiki/Eq ··· sistance

/tom
LittleBill
join:2013-05-24

LittleBill

Member

so overall, is a hertz of 59-62 a concern for standard house hold electronics?

whats your opinion on whether or not the generator will cause damage

thanks for the info

mackey
Premium Member
join:2007-08-20

mackey

Premium Member

said by LittleBill:

so overall, is a hertz of 59-62 a concern for standard house hold electronics?

No, most will happily run on 45-70 Hz.
said by LittleBill:

whats your opinion on whether or not the generator will cause damage

It's unlikely for any damage to occur.
b10010011
Whats a Posting tag?
join:2004-09-07
united state

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What UPS are you using? My company makes UPS's and ours are set to +/-3Hz standard and can be set as wide as +/-5Hz for use with mechanically governed generators.

Maybe your UPS can be set to not be so frequency sensitive.

As for your SMPS I would not worry as the basic SMPS design makes them operate on a wide frequency range. 40Hz to 70Hz is not an uncommon operating range for a SMPS
Mr Matt
join:2008-01-29
Eustis, FL

Mr Matt to LittleBill

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to LittleBill
said by LittleBill:

that said i googled my ups and they actually indicate they will not generally work on the generator due to the hertz needing to be within .5 htz.

UPS systems use a change in line frequency as an indication something bad is about to happen to utility power as described here:

»en.wikipedia.org/wiki/No ··· _of_1965

"Comparisons of segments of the hit songs played at the time of the broadcast, minutes before the blackout happened, in this aircheck, as compared to the same song recordings played at normal speed reveal that approximately six minutes before blackout the line frequency was 56 Hz, and just two minutes before the blackout that frequency dropped to 51 Hz.[citation needed] As Si Zentner's recording of "(Up a) Lazy River" plays in the background – again at a slower-than-normal tempo – Ingram mentions that the lights in the studio are dimming, then suggests that the electricity itself is slowing down, adding, "I didn't know that could happen"."

EliteData
EliteData
Premium Member
join:2003-07-06
Philippines

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in your case, the only things i would be worried about concerning a SMPS operating at different frequencies on generator are the following:
too low a generator operating frequency and the SMPS will "ramp up" its output to keep the specified voltage and current at level and may cause the SMPS electronic components to generate more heat which may cause failure (because the input voltage is too low).
too high a generator operating frequency and the bridge rectifier capacitors may start to overheat and fail (because the input voltage is too high).
as far as powering your TV with the generator, a range between 59-62Hz is perfectly acceptable for it to operate and function without damaging the TV's SMPS.
during hurricane Sandy, i was able to dumb down the generator to 50Hz in order to consume less fuel, all of the electronics including the cheap UPS, TV and refrigerator operated for a month without any issues though the refrigerator took longer to cool (slower compressor speed).
TheMG
Premium Member
join:2007-09-04
Canada
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said by LittleBill:

no my microwave works fine. but my motion light and my 1 electric blanket, both electronic controlled would not work while on generator power.

I'd have to say they probably have poorly designed electronic controls.

That generator voltage waveform really isn't that bad. I'd say any electronic device that malfunctions on that waveform is probably poorly designed.

aurgathor
join:2002-12-01
Lynnwood, WA

aurgathor to LittleBill

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to LittleBill
The great majority of switching PSs can take most any reasonable waveform and work just fine. Some with active PFC can be more picky, however.

UPSs in general a lot more picky, and I can think of 3 reasons for switching to battery:
a) incorrect peak voltage (either too low or too high) or too much variation
b) incorrect frequency or too much variation
c) too high harmonic content that confuses electronic

c) is the easiest to deal with -- just a low pass pi filter (2 caps & 1 coil at the minimum)
b) is mostly a function of the motor and its control so there isn't much you can do there, although if you have an option to get a heavier or a dual mass flywheel, either one could help
a) I'm not sure if there's any adjustment for voltage, but you can combat occasional high voltage spikes with Zener diodes (you need at least 2 zeners and 2 fast rectifiers)
Of course, a better generator should help with all of the above.