UPS, PWM Sine wave or True Sine wave

[theokie]

So I really don't consider this DIY, as it's just hooking batteries up, but didn't know where else it would fit. Also in order to save time before heading to work this is basically cut and paste from what I posted on a larger forum and have yet to get a response from. I'm hoping that any information gained from this will be valuable for others in rural areas where winter power losses are common and big all in one UPS are astronomically priced so here goes.



So I'm looking to setup a UPS for my return pumps and skimmer and came across this

http://www.tripplite.com/en/products/model.cfm?txtModelID=2938

And was wondering if the PWM sinewave would damage my Blowhole 1450 pump, as I know the transformers in my DC pump power supplies will filter out the wave form anyway.

Or should I just swallow the 200 dollar greater price and buy the

http://www.amazon.com/gp/product/B006R64SM2/ref=s9_simh_gw_p263_d0_i2?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-2&pf_rd_r=04C2CSF82E72XQ7EQSQ5&pf_rd_t=101&pf_rd_p=1630083502&pf_rd_i=507846

I plan to use marine deep cycle batteries wired in parallel to give me about 200 to 300 Ah as I live in a rural area that routinely looses power for several hours during the winter snows. I know a generator is ideal, already have one, but it doesn't start itself, so needing a way to keep the tank going for up to 9 hrs during the work day.


Also would this unit be trust worthy
http://www.ebay.com/itm/3000W-1000W-12V-110V-PURE-SINE-WAVE-INVERTER-35AMP-CHARGER-WITH-LCD-SCREEN-/330795861636?pt=US_Power_Inverters_&hash=item4d04f84684
As it's CE AND FCC labeled

[banditpowdercoat]

The pump will be fine. Some little powerheads make a bit more noise on a square wave, but thats about it.

And I often loose power too. I'm a softie tank, 150g, No SPS, but the tank has experienced many 8 hr power outages with no issues. I think they fared better than me

[theokie]

Thanks, for the advice. My tank made it thru fine last winter with the power outages, but now that there is several thousand in live stock in there, and I travel more I am wanting the peace of mind the pumps will keep running. Well that and the other half may has demanded it, for their peace of mind while I'm away.

If the manufacturers had just stated square wave, I would have understood, but now that I think about it PWM is just a variable square wave, and well if the Blowhole pump doesn't like the power, I just take the 200 bucks I had saved and swap it out for a DC model. And it appears the more coffee I drink this morning the longer and longer my run on sentences get.

And thanks again, I know enough about electronics to dabble more then most, just enough to be willing to experiment, but not enough to speak with the knowledge of a guru

[mike31154]

Not much info available on the "PWM Sinewave" output of the tripplite UPS unit in your first link. I'm guessing it's a modified sinewave much like most lower cost inverters and wouldn't take the chance on it to run an AC pump like the Blowhole. Could get costly having to replace your return pump. Having said that, have you considered one of the DC voltage return pumps that are slowly making their way into our hobby? For the price of one of those and a sensing relay plugged into an AC outlet, you could DIY something that would work pretty much the same way as the costly UPS. This would require a bit of knowledge as to how to wire the relay to switch to battery power when your AC power fails.

The other two units (pure sine wave inverters) look good for running your Blowhole pump, but pretty costly as well. But it appears they also have a 'transfer' switch feature which will make them plug & play.

If you experience power outages that often in your area, you might wish to consider investing in some 'off the grid' technology such as solar panels, wind generator, micro hydro if you have a creek nearby etc.. Initial investment is costly though & definitely some diy involved if you wish to save some money. Or bite the bullet & get a Generac natural gas whole house unit. There are some smaller ones available these days and they will automatically kick in & run most of the essentials in your home during an extended outage.

[theokie]

Mike,

I've considered going the relay route to do my switching, and then having a separate battery charger and inverter, but the other half just started pointing to my tank and adding up a few corals, and then vetoed it. Since I travel for work, the other half wants a plug and play solution, just in case I have to do over the phone trouble shooting. Unfortunately the other half won't touch a multimeter, but I was allowed to cut holes in the wall, so I shouldn't complain.

The other two pumps that I would be putting on the UPS are DC pumps already, I only have 2 AC pumps in my entire 300 gallon system, so replacing the Blowhole is an option I've considered.

The power outages have gotten fewer the past few years, milder winters perhaps, but we have discussed a whole house unit before, and its been slated to be in the new construction we are building in 5 years, along with some alternate energy, depending on location.

This is more to keep my spouse happy, as my current job has me traveling more then my previous job, as I know my tank is okay for a few hours, as I already have a piston air pump on a computer UPS that I built a relay box to kick on when the power is out, just to circulate and aerate.

Thank you again, I was unsure if a PWM sine wave was square or a bit closer to a true wave form, but it appears, I'm just going to have to bite the bullet or rather cut in to my coral budget for the next month or two.

[theokie]

Some more searching and I came across this image
http://www.wikihow.com/images/b/bd/SUMPPUMP.jpg

A few diodes and this would do it, just have to sell the other half on this, pretty picture might help. As with the cost of this type of setup, I could get a DC pump to lower the power consumption, and have the backup, for the cost of just buying the backup. I guess its time for the hard sell to the other half

[mike31154]

Mike,

I was unsure if a PWM sine wave was square or a bit closer to a true wave form, but it appears, I'm just going to have to bite the bullet or rather cut in to my coral budget for the next month or two.

Yeah, I've never heard a manufacturer of inverters use the term PWM sine wave. I know that the cheaper inverters with 'modified' sine waves have 'chopped' peaks, so not really a true square wave either, as they try to time a bit of a slope into the wave to make it more sinusoidal. To me PWM can mean many things, including a modified square wave with different frequency and all kinds of nasty permutations. In other words, not only can the amplitude of the wave vary from one wave to another, but also the 'off' time between waves, i.e. the width between pulses, which is a sort of frequency modulation. I would hope that something PWM designed to emulate an AC sine wave would very closely mimic such sine wave, but it's still not a pure sine wave, so probably not the best option to run an AC motor. I could be wrong & they've figured out how to time the pulses to make a pure sine wave, who knows. More research required....

[banditpowdercoat]

High dollar Inverters I work with all the time at work, Industrial Electrician, All use PWM, not a true sign wave. We control speeds via frequency from 3Hz up to 400, All PWM. So no worries on a induction motor. The motor itself, The coils that its built form actually smooth the Pulsed waveform into more of a sign wave. And AC/DC supplies transform the power lower first through a transformer, a coil, then rectify to DC so no worries on PWM inverters for them either. Like I said, Only thing I ever noticed was small powerheads were a bit noisier. The PWM makes them chatter kinda like. Nothing bad. Just smaller motors with the high impedance coils.

And most all UPS run direct off the mains when the power is on, Only after the Mains is out, they swap over to battery. So, only running PWM when the power is out. Will be direct off the house sypply, bypassing the UPS electronics when the power is on

[KrazyKuch]

all inverters use PWN to generate the sine wave, Just more expensive ones do a better job...From what i have found in the past is motors need to be rated for ups use, you will find when the motor is running off the batteries it will sound funny, but shouldnt burn out your pumps...

[mike31154]

I guess it comes down to 'efficiency'. I can remember when inverters were 'motor-generators', before there was such a thing as an electronic inverter. They were large, noisy & needed periodic maintenance... replacement of brushes, bearings etc, but they produced the purest sine wave out there. The purest sine wave is still produced by something like this, a DC motor attached on the same shaft as an AC generator, which essentially rotates at the desired frequency & produces the desired voltage amplitude. Not unlike a common generator that uses a gasoline or natural gas fueled combustion engine to spin an AC generator. And remember that your household AC is a pure sine wave. Hence, most of the equipment, as in motor(s), you wish to run off the 'inverter' will run best & most efficiently on a pure sine wave. I'm sure there are newer AC motors out there these days that are optimized to run well on modified sine waves or PWM signals, but I would wager most of the AC motorized equipment used in our hobby prefers a pure sine wave. I think DC motors will increase in popularity in our hobby, since they are much easier to control and a lower voltage around water is always a good thing. So if you have a DC power supply & DC motor/pump, you don't need an inverter! One less piece of gear. Every time power is converted from one form to another, you lose some efficiency in the conversion process. Not a big deal necessarily, but for something that runs 24/7, like a return pump or powerhead, the more efficient, the greater the savings. That can be applied to your back up as well, run a DC motor off your 12 volt battery instead of using an inverter with a funky wave to run an AC motor and you'll probably get more running time during an outage.