On Tue, 17 Mar 2009 17:38:20 -0400 Michael A. Terrell wrote:
| Sigh. Do it. Design it, build it, and use it. Then see what | happens during a brownout.
I'll buy it when it comes out as an integrated product.
|> Not everything has to be larger. | | | Give details on what doesn't need modified, since you have all the | answers.
It's an integration project. Just put a wide range power supply in place of the narrow range power supply, and change the control logic to allow wide range operation.
|> If it is a limited power device, then the current could double for half |> the voltage. Components dealing with the incresaed current will need to |> be larger. Once the device has the voltage at a fixed working level to |> derive other voltages, then part is just the same size. |> |> If it is a limited current device, then very little will need to be |> increased in size. There will have to be added the circuitry to limit |> the current when it reaches a certain level. | | | If it is current limited, it will be of little use. The existing | charger may take up to 24 hours for a complete charge, and would give | you less than 10% of the battery's A/Hr rating. Think about it: 24 | hours to fully charge, and 15 minutes to run them down.
The current limit is for operation at lower voltage, reduced power. One doesn't recharge the battery unless there is sufficient input power available to do that. Many current UPS designs use about 1 amp input to recharge after a long usage. Rapid recharge is not much of a demand. It could be done, but as you know, you'll need a larger circuit for it.
|> | High current supplies like that can catch on fire. The Northern |> | Telecom PBAX telephone system we had at Microdyne caught fire and smoked |> | damaged 80,000 square feet of office, engineering, production and |> | storage space. It took over three months to repair the offices near the |> | fire, and you could still smell the smoke a year later. Our insurance |> | paid for all the repairs, then sued the OEM. The damage came close to |> | putting us out of business. Luckily, the phone room was in the |> | engineering department, and some of the people could work from home, but |> | it dropped productivity quite a bit. If any part of that system was |> | home brewed, we would have had to pay for the repairs ourselves. The |> | system was in a locked room, and caught fire late one night. if someone |> | who was driving through that industrial park hadn't noticed the orange |> | glow, we would have lost all the offices, both stockrooms and all of the |> | engineering department. |> |> If we are dealing with a constant power device, then a 1000 watt model |> will have current levels at half voltage similar to a 2000 watt model at |> nominal voltage. Are you saying that the 2000 watt model is more of a |> fire risk than the 1000 watt model ... AND is so much more of a risk |> that such current levels should be avoided? | | | Constant load, maybe, but there is the law of 'Conservation Of | Energy', and all your dancing can't get yo around that. You have losses | every time a conversion is made, which adds to the heat load for the | building. If you don't remove the heat, the equipment dies a lot | faster, adding to the capital equipment costs.
So you think there is more heat produced at lower power?
|> If we are dealing with a constant current device, then "high current" is |> a constant. | | | The only constant current is into the load. if there isn't enough | available, you get data errors, or crashes.
The idea is to provide a constant voltage to the load, and shutdown when not enough power is available to do that.
|> |> | Third, AC utilities providing voltages at that low level is a |> |> | specification violation. It rarely happens. If detected, utility |> |> | typically cuts all power off due to defects that might cause such low |> |> | voltages. IOW a more complex UPS circuit and the larger battery |> |> | charger would rarely prosper from such a condition. Better is to get |> |> | you to buy a larger (more expensive) UPS - and keep this UPS as cheap |> |> | as possible. |> |>
|> |> Utility equipment is also done on the cheap. I've seen the half voltage |> |> scenario ssveral times in different places. In one instance it persisted |> |> for over 4 hours. In theory, a phase loss detector in a transformer should |> |> signal an upstream cutoff. It doesn't always happen. |> | |> | |> | Phase loss detection is the customer's problem, and is solved by using |> | a PLM and either drive an alarm, or use it to shut down equipment that |> | is easily damaged. There was a company in Leesburg, Florida making |> | them. They were small enough to hold in your hand and made to mount |> | with typical industrial relays and timer modules. if you lose a phase, |> | but have some large 3 Phase AC motors running at the time, they will |> | continue to run, but draw the additional current from the other phases, |> | causing the motor to run hotter. Look up 'Rotary Phase Converter' |> |> If a phase loss results in nominal voltage on 2 phases and zero on a |> third phase, then that would be a phase loss to the customer. However, |> if the utility wires things in such a way that a phase loss upstream |> results in half voltage to SINGLE PHASE customers for an extended period |> of time, then that is a utility problem. | | | It is their responsibility to make quick repairs, it is up to the | customer to protect their equipment.
That doesn't always happen, for many reasons.
|> |> This is one reason (there are others, too) I'm wanting to run my computers |> |> directly on 240 volts. If there's a deep brownout, they can still run in |> |> that condition. The impediments to doing this include finding the right |> |> surge protection (easy for entrance protectors, hard for point of use) and |> |> the fact that existing UPSes defeat the ability to operate over the wide |> |> voltage range (why I raised this issue to begin with). |> | |> | |> | Take a careful look at the power supplies you are considering, |> | because a lot have a dead band between the two voltage ranges. All they |> | do is sense the input and select 120 or 240 range to keep the costs |> | down I see them specified as 90-130 & 180-260, leaving a dead band |> | between 130-180 volts where operation isn't guaranteed. |> |> Many are that way. Many more are full range. Full range is becoming |> more and more common. Maybe you should take the careful look. | | | I have, and I don't like the specifications on a lot of them. Too | much ripple, and other problems. Look at the efficiency of some when | not operated near the two nominal voltages, as well. There are no idiot | proof designs, but overly complex designs will come back to cause major | problems, more often.
I have found that computer power supplies of the 100-240 volt design do run more efficiently at 240 volts. Is that what you are referring to?
|> |> A battery charger (in a UPS or as part of a separate component system) |> |> that can be set to specific power or current limits can also be useful |> |> in using small generators to supplement the battery in a total loss of |> |> power. |> | |> | |> | if you buy a small generator, get one with an accurate governor, or |> | that is a DC/inverter package like some of the Hondas. |> |> And regulator. | | | Show me any commercially available genset designed for autostart & | transfer switch that isn't regulated properly.
Use your own Google.
|> |> | Fourth, if a low voltage condition exists, unstable AC power is best |> |> | disconnected from equipment anyway. Maintaining voltage too low can |> |> | be harmful to electric motors and to the distribution system. |> |> | Therefore, when that defect is detected, reliability says better is to |> |> | disconnect. |> |>
|> |> For anything that increases the current, and is not rated for that increase |> |> in current. That's why my idea of making the power supply component have a |> |> current limit and just scale down its power intake, stretching the battery |> |> run time. |> | |> | |> | You can't limit it very much and have anything useful. |> |> With limited current, you can have half power at half voltage. That may |> only be half as useful, but it can be useful. For example, if the UPS |> is fully loaded, half the power needed to run the loads can be drawn |> from AC and the other half from the battery ... instead of all from the |> battery. | | | Like I said several times before, the waveform is less than ideal during | brownout conditions. Do you monitor the line voltage with a true RMS | meter, or a cheap DVM? You need to look at the AC line with a scope | during brownouts, and other problems to see what crap the equipment has | to deal with.
I'll let you know.
|> |> | Fifth, a UPS is for saving data. Making the UPS more complex for a |> |> | rare type of failure is not useful. If a UPS needed to operate |> |> | longer, then the UPS is too small anyway. Better is to get you to buy |> |> | the more expensive UPS with a bigger battery. |> |>
|> |> What the UPS is for depends on the scenario. In many cases I have seen, |> |> especially for ISPs and web services, it's to ride out power outages. |> |> The sizing is done by CFOs. Batteries are the biggest part of the cost. |> | |> | |> | If the CFO is so cheap that he is willing to use home brew backup |> | power, its time to find another job. The costs to get a custom system |> | through UL approval will buy several lifetimes worth of batteries. Do |> | you have a PE willing to sign off on your modifications? Will you be |> | able to find fire insurance for the business that will pay a claim after |> | a fire? |> |> The CFO sets the price limit. It's called a budget. Engineering can |> sometimes wiggle this some. But not always. Or not generally by a |> great deal. | | | A budget is a goal. Some are reasonable, some aren't. Sometimes you | have to walk away from the CFO and let them find out for themselves. | BTDT. They told me I was unreasonable with my costs, then found out | everyone else wanted three to ten times as much. In some cases they | spent the money. in others, they had to scale down their plans, or | delay them till more money was available. A CFO operates on greed. | Engineers operate on logic.
And what do you techs operate on?
|> So, where batteries are the substantial cost, and there is the real |> possibility of getting half the voltage for some reason, then a UPS |> system that works this way and provide more run time on that fixed |> battery capacity. | | | SO what? Either you can afford to be in business, or you can't. It | sounds like a shoestring operation that is about to close its doors.
Or a startup. Or in survival mode. Businesses do pull through when money has a dry spell.
|> There is a valid market issue. Is there a market for such a device? |> Probably not. Can it be designed? I think it can. The components have |> already been done. | | | Give links to the available equipment, the additional material costs, | labor, and costs for rent for the floor space for the additional | equipment, the extra air conditioning costs, preventative maintences | costs, stocking spare parts for the custom equipment, documenting the | project, and estimated service life before it needs a major overhaul, or | complete replacement. Then compare that to the battery costs for a | decent genset & switch plus fuel. Then figure out what would happen if | you needed to increase the capacity, say another 20% because the new | servers needed it. You never want to design a system too close to the | limits, like I have pointed out before. A proper de-reating is needed. | If you do get extended time for the servers, what happens when they | overheat because there is no AC?
I'm suggesting that it be designed, not suggesting that it already exists.
|> |> | Those UPSes are designed to sell mostly on price - as cheap as |> |> | possible. Why do anything to make its price higher? Five different |> |> | reasons why the suggestion is not useful. |> |>
|> |> An increase in charger cost, that can provide longer batter run time than |> |> an the increase in battery capacity of the same cost, provides more run |> |> time for the dollar. |> | |> | |> | Not if it isn't legal to use. If the fire inspector sees a homebrew |> | UPS during any visit, he is allowed to have the power to the building |> | turned off till it is removed. You still don't see the big picture, |> | Phil. Its one thing to homebrew a power supply to use at home, but for |> | a business, it is a huge liability. |> |> If it is an engineered custom design, this is not true. Businesses have |> various kinds of systems custom designed for them all the time. | | | If it is custom engineered and can affect employee safety, someone is | liable if it has a catastrophic failure.
And?
|> |> This is why I often have the desire to just build a UPS from separate |> |> components. I'm not an electrical engineer. At best I am an electrical |> |> hobbyist. |> | |> | |> | Do the math, Phil. The extra hardware costs, plus the testing & |> | added liability costs quickly wipe out any possible savings. An |> | properly sized generator with an automatic transfer switch is cheaper |> | than getting a custom UPS approved for commercial use. if the generator |> | is propane powered, it won't have a problem with the fuel going bad |> | while in storage. |> |> If YOU have done the math on the hardware component costs, then YOU have |> done a design. | | | I have doe it before, and it never made sense. I don't have the | numbers in front of me to do a full design, but you should, even before | considering a custom system.
So you have had a NEED to make a UPS like I suggested?
|> |> I've known many technicians (and engineers). I've also listened to a few |> |> radio talk show hosts, and watched equivalent ones on TV (such as Glen Beck). |> |> Most manage to remain respectable. There are exceptions like Michael and |> |> Rush. |> | |> | |> | Why? Because I tell you something is flawed, and you never listen? |> |> It's more a case of not believing you because you have a track record of |> saying some of the dumbest things I've heard online. | | | Funny. I heard that, and more about you.
Maybe my suggestion is a dumb one. But you've not yet given a sane argument why it would be. Your posting style is more along the lines of giving dumb answer and making insults without details. I'll continue to think outside the box and come up with ideas. There will be dumb ones. Those are supposed to be shot down on merit, or just ignored. Your past reactions have been some combination of insult and ignore. You're not useful.
|> | I have worked in electronics my whole life, including manufacturing of |> | power supplies. I also qualified new suppliers for the few switching |> | power supplies we bought, and dequalifed multiple vendors when the |> | shipped product didn't match the build quality of the test samples. One |> | of the TV stations I worked at had 500 KW diesel generators for backup |> | power, and the only UPS was for the video automation computer. A few |> | battery powered emergency lights were mounted around the walls, but if |> | the three generators didn't start, two UHF TV stations, five 50 KW FM |> | stations, trunked business radios and multiple government agencies were |> | without power for their equipment. |> |> You've told us about some of your experiences, before. | | | So have you, but you seem to always omit any details needed to help | you.
Where the details would be relevant, I'll provide them.
|> |> I've learned years ago that when I see someone insulting someone else online, |> |> and not just on Usenet, that it more likely means the insulter is upset at |> |> something. I've also learned that it can be hard to find out just what that |> |> is because so many cases are merely a misunderstanding somewhere. |> | |> | |> | The only way to get some people's attention is to resort to insults |> | and you are know for hurling your share of insults, as well. |> |> I go to extra effort to avoid using insults. For a few people like you, |> that gets to be very hard to do, and sometimes it just has to happen. |> But check your own posts. You'll see insults generally begin with your |> first followup post in the original thread. | | | You still haven't given anything useful, other than your usual wish | list. No good design starts with a dart board or 'magic 8 ball'. | Solid, reasonable specifications are always the first step. Without | those, it is a complete waste of time.
Yes, I do toss out wish list items. Now you're recognizing that. And of course some will be usless in the market and others impractical to make. You seem to have a lack of ability to properly recognize either reason.