Bad Power & Effects Upon PSUs

[Capt. Cap]

We have not-so-great power at our house (lights dim when refrigerator kicks on, lights flicker while running washer) and I was wondering what sort of effect this has upon modern SMPS PSUs.

Is it no big deal with the mains filter capacitor doing its duty to give consistent supply to the rest of the PSU? Or is it putting undue stress on the components?
Has anyone seen this sort of bad power having effects that make it all the way through a modern PSU to the rest of the electronics?

I was thinking about getting an uninterruptible power supply for a new TV not so that I can watch it when the power goes out, but for the voltage regulation.

[stj]

Re: Bad Power & Effects Upon PSUs

you need to put a lamp after your meter - or before it.
see if that flickers - because if not, your looking at a fire waiting to happen.

[Quaddro]

Re: Bad Power & Effects Upon PSUs

That's depends on your psu.

Old design ppfc psu is more reliable for this condition (on off, unstable input etc) rather than new modern apfc psu.

Why?
Because of simple system need no sophisticated ic.
Most of old design just need 3 main ic, like 339, 494/7500/ and tl431.

More complex the design, more ic will needed.
More ic, somehow add more failure possibilities.

And ic functionality is really depends on stable input..

I'm not really worry about the bulk caps.

[stj]

Re: Bad Power & Effects Upon PSUs

forget the psu for now,
it sounds like he has a bad / loose connection in his house wiring!

[xelectech]

Re: Bad Power & Effects Upon PSUs

Maybe a poor incoming neutral connection, not good for things hooked to it, especially electronics. If you can monitor the voltage both during the flickering and when not you might gather some more clues.

'Course, it might just be poor connections somewhere else, like in the piece of gear itself, or the power/wall switch, etc., but make sure you don't have a floating neutral problem that is progressing.

Good idea, putting the new TV on a UPS, along with any other electronic equipment you care about 8-)

[stj]

Re: Bad Power & Effects Upon PSUs

i dont think ups monitor for over-voltage - only under.

[xelectech]

Re: Bad Power & Effects Upon PSUs

i dont think ups monitor for over-voltage - only under.

Now I'm kinda wondering, would a ups maintain a correct output if it happens to be plugged into a 120vac line that has a floating-nuetral problem, or would its operation be somewhat flaky too - guess the quality of ups may be a variable, also.

[stj]

Re: Bad Power & Effects Upon PSUs

if it's like mine, it's input side would explode - it's packed with MOV's!!!!

[eccerr0r]

Re: Bad Power & Effects Upon PSUs

My old bestpower UPS monitors both over and undervoltage - and switches to battery power under either situation. Thus it depends on the UPS.

[budm]

Re: Bad Power & Effects Upon PSUs

forget the psu for now,
it sounds like he has a bad / loose connection in his house wiring!

+10
Start by checking the connection at the circuit breaker panel, to be safe and if you are not sure, get licensed electrician.

[sam_sam_sam]

Re: Bad Power & Effects Upon PSUs

How far away are you from the main power lines to your house ?
How may houses are on this transformer ?

My house is over 250 feet from the main power lines I am the only one that is on this transformer and my light would dim a lot when the A/C unit turn on

The volt reading at the outlets would be at 108 to 110 most time

I live in an area where there is only one feeder high voltage line that goes down our street and there two housing developments that have about 50 homes each
There is a step up transformer on this line that feed this area there really should be two feeder line not one we live about 20 miles from town and they do not care about us out here

Call the electric company and had them come out to my house and when they read the voltage that day it was 106 according to there meter so they changed the tap on the transformer and now I get 119 to a high reading of 122 but most of the 120 to 121 volts

So now when the A/C unit come ON it only dims the lights a little bit

I also have a capacitor bank on the main breaker panel this has help a lot for this same problem I know this because when I turn unit OFF the lights dim a little bit more

I would also do what Budm has in his post also
I would also look at what Stj had in his post as well

I had checked the items that were in Budm and Stj post before I called the electric company

What xelectech has in his post

i also had this happen to me not the house that was taking but in another house it caused some real problems because the neutral wire was pulled loose from the pole and instead of 120 volts at each outlet you get some weird reading it happened many years ago and I do not remember what the reading were


I hope this will help

[PeteS in CA]

Re: Bad Power & Effects Upon PSUs

I agree with S_S_S. Are you in a really old part of SF, Capt. Cap, with house and/or power pole wiring dating back to a little after the 1906 quake. If your wiring is a century old it probably isn't adequate for the load of modern appliances.

Monitoring what happens to your AC voltage at the fuse or breaker panel when your refrigerator compressor or washer turn on should tell you about the quality of the power coming into your house. If the voltage droops there the problem is your pole transformer or the wires to your house. You might call PG&E if that's the case, but is those are in good shape but heavily loaded they probably won't do much.

For your inside wiring, throw the breaker or remove the fuse for a certain outlet, pull the outlet from the wall, and have a look at the wires. If the insulation looks really old and the wires are not 14 or 12 gauge, your house wiring is probably the problem. It was probably wired for 1910s-1930s loads, and you'd have to rewire the whole thing. Doing that would be very expensive and possibly open some cans of worms better left alone.

As for your power supplies, they are designed to handle surges and sags. If you have good quality power supplies the main thing to worry about is voltages to you MB and system going high ripple, out of regulation, or shutting down. Data could be corrupted.

If there is an inductive surge after a sag the power supplies' surge protection devices should handle it. BUT, if the surge protection is MOVs, those are damaged a little every time they absorb surge energy. Over time they break down to the point that they conduct continually and fry themselves. Your power quality could cause this if there are frequent surges as well as sags.

If the quality of your power supplies is mediocre or worse, sags will cause the main loop to go to full pulse width. That may not be handled well by power supplies of lesser quality. Poor Gate/Base drive or wimpy MOSFETs/BJTs or marginal transformer cores could cause a destructive power supply failure.

[Capt. Cap]

Re: Bad Power & Effects Upon PSUs

Thanks everyone for the many responses!

+10
Start by checking the connection at the circuit breaker panel, to be safe and if you are not sure, get licensed electrician.

I've had the electric company come out and replace the connectors for the drops, and also took a day off work to meet with an electrician. I think the company that sent the "electrician" out forgot about the appointment, and scrambled some guy over at the end of the day (who turned out to not be a licensed electrician). He showed up at about 6 PM, poked around for about 15 minutes not really doing anything and said we should consider upgrading the service panel and rewire the house, which would cost $15-20k (hence me asking about UPSs). He really just seemed like he wanted to leave before he got here, wouldn't even pull the breakers when I asked him to check those out. He also didn't think our situation was that bad FWIW.

forget the psu for now,
it sounds like he has a bad / loose connection in his house wiring!

Maybe a poor incoming neutral connection, not good for things hooked to it, especially electronics. If you can monitor the voltage both during the flickering and when not you might gather some more clues.

'Course, it might just be poor connections somewhere else, like in the piece of gear itself, or the power/wall switch, etc., but make sure you don't have a floating neutral problem that is progressing.

Good idea, putting the new TV on a UPS, along with any other electronic equipment you care about 8-)

What would a loose neutral look like on the voltage while monitoring the flickering? I thought I would need a scope to really see the variations, which I do not have, is a DMM sufficient?

My old bestpower UPS monitors both over and undervoltage - and switches to battery power under either situation. Thus it depends on the UPS.

if it's like mine, it's input side would explode - it's packed with MOV's!!!!

OK will need to make sure that the UPS is built for power conditioning overvoltage. That's probably going to be hard info to find on consumer-grade UPSs. I was hoping I just needed one that included "power conditioning" as a feature.

How far away are you from the main power lines to your house ?

very close

How may houses are on this transformer ?

Not sure, but the guy from the electric company agreed with me that the wiring is pretty bad in our area, but they're not going to do anything about it unless the voltage is waaay out of spec.
From what I remember, voltage varies from about 110-120 throughout the day.

My house is over 250 feet from the main power lines I am the only one that is on this transformer and my light would dim a lot when the A/C unit turn on

The volt reading at the outlets would be at 108 to 110 most time

I live in an area where there is only one feeder high voltage line that goes down our street and there two housing developments that have about 50 homes each
There is a step up transformer on this line that feed this area there really should be two feeder line not one we live about 20 miles from town and they do not care about us out here

Call the electric company and had them come out to my house and when they read the voltage that day it was 106 according to there meter so they changed the tap on the transformer and now I get 119 to a high reading of 122 but most of the 120 to 121 volts

So now when the A/C unit come ON it only dims the lights a little bit

I also have a capacitor bank on the main breaker panel this has help a lot for this same problem I know this because when I turn unit OFF the lights dim a little bit more

Oooh didn't know they made service panels with capacitor banks, I'll have to look into that.

I agree with S_S_S. Are you in a really old part of SF, Capt. Cap, with house and/or power pole wiring dating back to a little after the 1906 quake. If your wiring is a century old it probably isn't adequate for the load of modern appliances.

The house isn't that old, but has a hodge-podge of wiring from different eras that is probably not helping the situation. It's mostly ungrounded, 12 gauge 20A circuits, but then some parts of the house that seem to have been remodeled in the 90s have grounded GFCI-protected branches.

Monitoring what happens to your AC voltage at the fuse or breaker panel when your refrigerator compressor or washer turn on should tell you about the quality of the power coming into your house. If the voltage droops there the problem is your pole transformer or the wires to your house. You might call PG&E if that's the case, but is those are in good shape but heavily loaded they probably won't do much.

You're spot on about PG&E
I'll take some measurements during daylight, thanks for the suggestion.

For your inside wiring, throw the breaker or remove the fuse for a certain outlet, pull the outlet from the wall, and have a look at the wires. If the insulation looks really old and the wires are not 14 or 12 gauge, your house wiring is probably the problem. It was probably wired for 1910s-1930s loads, and you'd have to rewire the whole thing. Doing that would be very expensive and possibly open some cans of worms better left alone.

We're both on the same page here

As for your power supplies, they are designed to handle surges and sags. If you have good quality power supplies the main thing to worry about is voltages to you MB and system going high ripple, out of regulation, or shutting down. Data could be corrupted.

If there is an inductive surge after a sag the power supplies' surge protection devices should handle it. BUT, if the surge protection is MOVs, those are damaged a little every time they absorb surge energy. Over time they break down to the point that they conduct continually and fry themselves. Your power quality could cause this if there are frequent surges as well as sags.

If the quality of your power supplies is mediocre or worse, sags will cause the main loop to go to full pulse width. That may not be handled well by power supplies of lesser quality. Poor Gate/Base drive or wimpy MOSFETs/BJTs or marginal transformer cores could cause a destructive power supply failure.

Excellent information, thank you!


So I've ordered an AFCI outlet that I'm planning to plug into each branch, power a lamp off of it while the washer is running and see if it trips.
If it does, then I know I've got a wiring problem.
Also, I'll be checking the breakers, along with taking measurements.
Any ideas what loose wiring looks like on a scope?

[stj]

Re: Bad Power & Effects Upon PSUs

if your comfortable around mains, pull the main fuse and then check all the terminals are tight on everything you can get at.

[xelectech]

Re: Bad Power & Effects Upon PSUs

Capt Cap said:

"I've had the electric company come out and replace the connectors for the drops, and also took a day off work to meet with an electrician. I think the company that sent the "electrician" out forgot about the appointment, and scrambled some guy over at the end of the day (who turned out to not be a licensed electrician). He showed up at about 6 PM, poked around for about 15 minutes not really doing anything and said we should consider upgrading the service panel and rewire the house, which would cost $15-20k (hence me asking about UPSs). He really just seemed like he wanted to leave before he got here, wouldn't even pull the breakers when I asked him to check those out. He also didn't think our situation was that bad FWIW."

That makes things look a bit better then, probably a fairly experienced electrician-in-training, rather than a sales-drone...

Cap asked:

"What would a loose neutral look like on the voltage while monitoring the flickering? I thought I would need a scope to really see the variations, which I do not have, is a DMM sufficient?"

The neutral conductor wouldn't necessarily be loose, could be just higher resistance due to either corrosion or oxidation at the incoming neutral conductor; or, it could be that tightening the lugs will take care of it; I consider it a maintenance item to re-tighten all lugs and terminals in my various breaker boxes occasionally, including adding a dab of Noallox to the incoming aluminum conductors if needed.

You could see 'floating neutral' with a DMM - for best results, you'd want to monitor both halves of your incoming 240 - as the fridge compressor comes on, its line voltage will drop, while the opposite phase will rise by the same amount. Also, any lights on the opposite phase will brighten according to the increase in voltage.

I had this happening to me shortly after I'd bought a new fridge about 15 years ago, and pulling the meter base and recoating the incoming conductors with Noallox and tightening the lugs in all the breaker-boxes took care of it; I should mention that I spent several months working for an electrician in my past working life and already had a good base in seeing it done and doing it, working on live electrical panels is not for everyone.

[PeteS in CA]

Re: Bad Power & Effects Upon PSUs

The house isn't that old, but has a hodge-podge of wiring from different eras that is probably not helping the situation. It's mostly ungrounded, 12 gauge 20A circuits, but then some parts of the house that seem to have been remodeled in the 90s have grounded GFCI-protected branches.

If you have 12 gauge wire throughout that should be good for that kind of current. Since you washer, refrigerator, and affected lights are probably on different circuits, that puts the voltage sag that affects the lights back at least at your service panel (since it has breakers instead of fuses, that's fairly modern). So your problem is probably a loose connection at the input to the service panel or (I^2)(R) voltage drops in the mains wire to your house or the pole transformer.

Caution! Most oscilloscopes ground the channel input ground terminals to safety ground. Touching the probe tip or ground wire to the AC circuit will cause an explosion, damaging the probe and possibly an oscilloscope. Exceptions would be Fluke or Tektronix handheld oscilloscopes. Whether powered by their adapter or by internal battery, their input grounds are isolated from safety ground and from channel to channel.

[RJARRRPCGP]

Re: Bad Power & Effects Upon PSUs

We have not-so-great power at our house (lights dim when refrigerator kicks on, lights flicker while running washer) and I was wondering what sort of effect this has upon modern SMPS PSUs.

Is it no big deal with the mains filter capacitor doing its duty to give consistent supply to the rest of the PSU? Or is it putting undue stress on the components?
Has anyone seen this sort of bad power having effects that make it all the way through a modern PSU to the rest of the electronics?

I was thinking about getting an uninterruptible power supply for a new TV not so that I can watch it when the power goes out, but for the voltage regulation.

Heads up! Go try your UPS on different outlets through the house and see if you find one where when a major appliance comes on, the voltage actually rises. For example, at the normal voltage range with no big appliances on, but with the furnace and range on, the voltage is at 131V or the like!

The symptom of a bad neutral, is an overvoltage on a leg that don't have a high load! The other leg will be sagging, for example, at only 111 V and possibly only 109 V or the like!

My incident in April, 2016:

https://www.badcaps.net/forum/showthread.php?t=53717

[xelectech]

Re: Bad Power & Effects Upon PSUs

https://www.badcaps.net/forum/showthread.php?t=53717[/url]

Just visited that thread, that's an excellent description of a floating neutral in the second post, thanks!

[Stefan Payne]

Re: Bad Power & Effects Upon PSUs

Is it no big deal with the mains filter capacitor doing its duty to give consistent supply to the rest of the PSU? Or is it putting undue stress on the components?

It stresses the PFC stage due and the primary capacitance.

You might want an online UPS.
Or at least get a PSU with as high primary bulk capacitance as possible.

This might be the only good reason to use a 1000 or 1200W PSU for a 300W system...

BUT:
Voltage Drops like this sound like bad connection in your electrical installation, if the cause isn't the line comin into your house...
But if it is NOT, it might cause a fire due to high resistance!!