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Testing UPS Output Waveforms

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Re: Testing UPS Output Waveforms

#71

Post by cyberax »

exmadscientist wrote: post #56
cyberax wrote: post #43

Earlier quoted context omitted.

I have thrown out my Tripplite UPS because its battery has degraded to the unusable levels. I replaced it with a 5kWh LiFePo4 rack-mounted battery and an AIMS rack-mounted inverter. I'm really surprised that there are no off-the-shelf solutions for this. The traditional UPS makers are just neglecting the recent 10 years of battery advances. I even made an Arduino-based module that provides an SNMP UPS interface for m…

> to avoid wearing out one side of the rectifier inside the PSU If you are seriously worried about this then the whole thing is trash. Either the design is marginal or it is not. You cannot possibly switch a relay fast enough to make a difference here (and have the relay survive).

I'm worried about long-term thermal wear from uneven heating, so I switch the current direction once a day. Simply because that's the maximum time I can set on a time delay relay that controls it.

Re: Testing UPS Output Waveforms

#72

Post by exmadscientist »

Dylan16807 wrote: post #66
exmadscientist wrote: post #56

Earlier quoted context omitted.

> to avoid wearing out one side of the rectifier inside the PSU If you are seriously worried about this then the whole thing is trash. Either the design is marginal or it is not. You cannot possibly switch a relay fast enough to make a difference here (and have the relay survive).

I don't understand what you're saying. If you're specifically worried about wear , then you could switch once a month and it would be enough.

Silicon rectifiers don't wear out.

(At least not on timescales relevant to individual humans.)

So hearing that makes me get suspicious that something else is going on.

Re: Testing UPS Output Waveforms

#73

Post by exmadscientist »

cyberax wrote: post #71
exmadscientist wrote: post #56

Earlier quoted context omitted.

> to avoid wearing out one side of the rectifier inside the PSU If you are seriously worried about this then the whole thing is trash. Either the design is marginal or it is not. You cannot possibly switch a relay fast enough to make a difference here (and have the relay survive).

I'm worried about long-term thermal wear from uneven heating, so I switch the current direction once a day. Simply because that's the maximum time I can set on a time delay relay that controls it.

Don't bother. That's not how these things fail, and one day is so so far beyond the thermal time constants involved that it's not doing anything useful. You would have to switch on timescales of seconds to minutes to do anything meaningful, and that would kill your relay in short order.

If you are truly close to the design failure point of the rectifier, it's not safe to run at all. (You are almost certainly not.)

If you are worried about the fact that you're only using one element of a multi-element package, again, it's a nonissue. We do this all the time. It's often cheaper to add a second bridge rectifier to get a single diode than it is to add another BOM line item for the "proper" part. As long as that diode isn't operating near absolute maximum ratings (it probably isn't), it doesn't matter that there are or aren't three more in the box.

Re: Testing UPS Output Waveforms

#74

Post by Dylan16807 »

exmadscientist wrote: post #72
Dylan16807 wrote: post #66

Earlier quoted context omitted.

I don't understand what you're saying. If you're specifically worried about wear , then you could switch once a month and it would be enough.

Silicon rectifiers don't wear out. (At least not on timescales relevant to individual humans.) So hearing that makes me get suspicious that something else is going on.

I'm also suspicious of the idea of that part wearing out, but if it doesn't matter at all then there's no reason to call things trash.

Your other comment says: If you are truly close to the design failure point of the rectifier, it's not safe to run at all. (You are almost certainly not.)

Well there's no reason to assume it's close to the failure point.

Think of it this way: Draw the line in the sand for where you'll approve the design, but just barely. If someone is running a diode close to that line, then it's not trash but trying to improve longevity isn't crazy either.

Re: Testing UPS Output Waveforms

#75

Post by dylan604 »

Dylan16807 wrote: post #67
dylan604 wrote: post #25

Earlier quoted context omitted.

If you get dips in voltage below the range that the PSU can handle, it will kill the PSU. If you get spikes higher than the range that the PSU can handle, it can kill not only the PSU but things attached to the PSU as well. Most people are familiar with spikes with things like surge protectors, but most are unaware of how damaging voltage dips can be as well.

> If you get dips in voltage below the range that the PSU can handle, it will kill the PSU. How does that happen? Let's say it's running and I drop the input to 80 volts. Why do I get any behavior that isn't "runs at reduced capacity" or "shuts off"? And what part of the circuit is failing? Are we assuming a combination of missing current limiting and a heavy load? If I'm just watching youtube then it shouldn't overl…

My experience is from older analog equipment. Specifically, I worked in a video/film post house that also had a VHS duplication department. Analog tape machines run at a certain rate. For those old enough, VHS had SP, LP, and SLP modes. Those were defined speeds that the tape was fed through the system. If the voltage dipped, the speeds would slow down. When played back at a constant rate, the signal could not be read as the signal wasn't recorded at that speed. So our meter would sound an alarm when the voltage dipped too low that would introduce that problem which would tell the operators to stop the recordings and rewind/restart. That's more of an annoyance than damaging, however, some of the records of a certain model would fail which was usually a power supply issue.

Same facility was fed 3-phase power, but due to some construction mishap nearby, one leg was cut. That lost us a lot of expensive power supplies that day for some of the more expensive equipment.

Those are examples, but not really an answer to the how question. I'm not an electrical engineer, so :shrug-emoji: I asked the engineers that question at the time, and they told me it was something along the lines of the equipment tried really hard trying to function instead of just shutting off. The dip was low, but not that low. Described like a ceased electrical motor where it keeps pulling more power where normally a breaker/fuse would trip, but something different. It wasn't a satisfactory answer then any more than it is now.

Re: Testing UPS Output Waveforms

#76

Post by exmadscientist »

Dylan16807 wrote: post #74
exmadscientist wrote: post #72

Earlier quoted context omitted.

Silicon rectifiers don't wear out. (At least not on timescales relevant to individual humans.) So hearing that makes me get suspicious that something else is going on.

I'm also suspicious of the idea of that part wearing out, but if it doesn't matter at all then there's no reason to call things trash. Your other comment says: If you are truly close to the design failure point of the rectifier, it's not safe to run at all. (You are almost certainly not.) Well there's no reason to assume it's close to the failure point. Think of it this way: Draw the line in the sand for where you'll…

The point is that the dance with the relay doesn't move the needle on design acceptance. If it is acceptable with the relay, it will be acceptable without the relay, because the component stresses will be the same.

So if it is unacceptable, it is unacceptable, and needs to be fixed. I said "trash" because it's going to become trash, and with luck just the power supply. Hope there's a fuse inline! Input rectifier failures tend to take down other stuff without one.

Re: Testing UPS Output Waveforms

#77

Post by Dylan16807 »

dylan604 wrote: post #75
Dylan16807 wrote: post #67

Earlier quoted context omitted.

> If you get dips in voltage below the range that the PSU can handle, it will kill the PSU. How does that happen? Let's say it's running and I drop the input to 80 volts. Why do I get any behavior that isn't "runs at reduced capacity" or "shuts off"? And what part of the circuit is failing? Are we assuming a combination of missing current limiting and a heavy load? If I'm just watching youtube then it shouldn't overl…

My experience is from older analog equipment. Specifically, I worked in a video/film post house that also had a VHS duplication department. Analog tape machines run at a certain rate. For those old enough, VHS had SP, LP, and SLP modes. Those were defined speeds that the tape was fed through the system. If the voltage dipped, the speeds would slow down. When played back at a constant rate, the signal could not be rea…

Well, I can think of a lot more ways for losing a phase to break things than a voltage drop.

For a voltage drop, the main idea that comes to mind is something trying to keep up a constant wattage and drawing increasing current to make that happen. But you have to do quite a bad job to design that circuit and not have a current limit.

And a PC power supply is inherently flexible on the input voltage, so it would never have the problems you get with a fixed ratio transformer on that old equipment.

Re: Testing UPS Output Waveforms

#78

Post by bombela »

Dylan16807 wrote: post #14
zokier wrote: post #3

its a shame that we don't have mainstream dc ups standards (telcos are their own niche). its kinda silly to generate fancy sinewave, manage transitions, and maintain phase of ac just to get immediately converted to dc.

There's not much to standardize, basically just pick a plug shape for your desired voltage and current, it's really about building enough desire for manufacturers to take interest. It's worth noting that there's already ATX power supplies that are built to run directly off battery power. They don't look all that impressive but they exist. https://www.powerstream.com/DC_PC.htm https://synoceantech.com/index.php?page=l…

How much does it cost and where to buy? If I have to call, I cannot afford it.

Re: Testing UPS Output Waveforms

#79

Post by Dylan16807 »

bombela wrote: post #78
Dylan16807 wrote: post #14

Earlier quoted context omitted.

There's not much to standardize, basically just pick a plug shape for your desired voltage and current, it's really about building enough desire for manufacturers to take interest. It's worth noting that there's already ATX power supplies that are built to run directly off battery power. They don't look all that impressive but they exist. https://www.powerstream.com/DC_PC.htm https://synoceantech.com/index.php?page=l…

How much does it cost and where to buy? If I have to call, I cannot afford it.

Okay so click on the first link I gave you.

And then scroll down to the model you want.

The second to last column is price. Click on that (Or click on the first column where it has the model number. Either one works.).

Then click "add to cart".

Re: Testing UPS Output Waveforms

#80

Post by butvacuum »

bb88 wrote: post #60
chimpontherun wrote: post #9

I've noticed that ALL the devices I plug into my UPSes have external power bricks. Most of them are either 5V, 12V, or 19V So, I replaced all my UPSes with LiFePO4 batteries supplied by Victron AC->12V chargers. Routed the battery contacts directly to all devices that consume 12V (WiFi AP, network hubs, SLA 3d printers). Used 12V -> 5V adapters to supply 5V / USB2 devices (R-Pi servers). For 19V, Drok DC-DC boost con…

I've been in the process of cutting the DC side of power bricks and crimping anderson power pole (APP) connectors onto both sides of the wire. For camping and ham radio, it's really nice to hook up to a battery without the AC inverter taking DC -> AC and the power brick sending that to DC again. The only thing to be careful with is connecting different voltages to different connectors, but it's at least possible with…

theres also anderson's SB series- APC seems fond of knockoff versions.
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