UPS to 1.5kW Sinewave Inverter Conversion part9 - Will it overheat?

[@knurlgnar24]

Thanks for the feedback, I really appreciate it! Used or refurbished forklift batteries are probably a great source for many of the little guys like me, except that I wanted something more portable. If I was making a stationary home power backup system I they would be high on my list.

[@gerardhandel2870]

As I said somewhere else: Your video series is GREAT!!! I am a newbie and learn a lot of from you. Excellent explanation and editing also. You clearly know what you are talking about and what you should talk about. Nothing too less, nothing too much. It's just excellent. n this video (part 9) I hear you talking about the quality of batteries. Somewhere on internet I found this: Get a fork lift battery! The 12 volt batteries that run fork lifts are the best!

[@knurlgnar24]

Possibly - good thoughts. Conduction and convection are linear with temperature increase and copper losses are less than linear so things would be going in the right direction to stabilize. Radiation loss changes with the 4th power, so that would help somewhat too. One also has to consider that when pushing a transformer far past it's intended operating conditions that localized internal temps will be much higher than the external core temp. I didn't want to find out where the limit was!

[@knurlgnar24]

The FET gate resistors are there for a few reasons: radiated emissions, to prevent the drive circuitry from excessive pulse draw, and most importantly to keep the voltage overshoot on the Drain and Source under control. At high currents if you switch too fast with too many parasitics the excessive voltage overshoot can damage the transistors. I'm not sure which combination of these factors is at play in this particular design as I do not have a good o-scope (or the motivation) to look.

[@victorreppeto7050]

I love your videos!!!! I am moving off grid on a shoestring budget and you have answered sooooo manny questions enabling me to move forward with my limited engineering skill set. Thank you!!Thank you!!Thank you!!Thank you!!Thank you!!Thank you!!

[@christopherjones3741]

Thanks for all the videos you have got my mind spinning with new ideas i wish you were my next door neighbor..i could help you out with that fab work..

[@EpicWinz]

Great video series. Perhaps just get a 1500w ups to begin with, to save the hassle of modifying it to shed heat. Maybe start with the XL version as they are beefier and can be run at full load constantly.

[@knurlgnar24]

The thermal conductivity of the thermal paste is irrelevant in practical application - you could use standard automotive grease and it would work almost as well. It's actually the thickness of the interface material that matters most since conductivity is directly proportional to the thickness of the interface material. For that reason thermal pads are less effective. Anything that removes all air gaps will work reasonably well, though.

[@IlluminatedWhiteGuy]

You could install a high performance low profile server CPU heatsink with fan on the back side of the transformer. The good copper core type with heat pipes can dissipate 200 watts of heat easily.

[@Peonygreenleaf]

Hey you should look up DD-WRT. It is a firmware for wireless routers that allows you to make a standard router do things the factory locked out like adjust the RF power or make it into a repeater.

[@garbleduser]

Just found 40 new old stock of the correct mosfets! Also, I acquired a full roll (1000) of the correct gate resistors. The audibility of the UPS should decrease and the efficiency may increase with the correct gate resistors and matched mosfets. These operate in the LINEAR REGION, so if the gate voltage is off, the units will be working against each other slightly. PLEASE show us the output on a scope!!! I predict a slightly distorted waveform. The internal noise produced by mine decreased when I plugged a large transformer bearing stereo receiver/amp into an AC output receptacle. Should I add a large homemade toroidal transformer to match or surpass the ratings of the original core? Great work BTW!

[@jamest.5001]

would epoxying small heat sinks to the transformer help it?

[@doubleas88]

I just found 2 of these exact same units and I am doing the same mods excepts one of them is currently the "donor" of parts for the main one I am wanting to use. I have already removed the fets and the large cap for use in my main as well as the transformer. my question is if I put the donors transformer in parallel with the one I am wanting to use in hopes of taking a high load off of the one transformer is there any possible problems I could have? I'm am planning to upgrade the wiring.. I'm am planning to cut the battery compartment out for room for the second transformer and extra much more quiet fans

[@dustinmerrill2331]

I know this was awhile back but, I have a question for you because I have the exact same unit. I was able to modify it to hold more amperage just like you did with the transistors. My question is is it possible to use two of them in parallel to get double the amount of amps? Because I know they sync the frequency and phase angle with the outlet with the wall.So my goal is to source the same PWM for both modules to output the same 120 V AC running off the battery bank.

[@knurlgnar24]

It's probably possible but my answer will be 'no' due to exact matching and sync needed. I did make a video where I put two of these units together to make a 240V unit that doubled the output power and that 240V could be fed through a transformer back to 120V. WHen put in series exact matching and exact sync is no longer a problem and it worked well.

[@dustinmerrill2331]

@@knurlgnar24 ok thanks for getting back to me. That’s a good point with two 1500 watt units in series. Then step back down to desired voltage. I’ll give it a try. I am very ambitious in cracking the code for parallel inverters, somehow making use of the synchronization logic inside the inverters. Another experiment I’d like to try is adding even more mosfets and “bypassing” the current transmitter so’s not to trip on overload. Just protect it with fuses. How many mosfets can you run in parallel without adding issues? Like remote mosfets totaling enough to run a whole house feeder? It’s ambitious but it’s fun.

[@Luis-2124]

todo los hornos microondas tienen un ventilador que refrigera el magnetrón y al trasformador, un ventilador de microondas encima del trasformador podria funcionar translate.google all microwave ovens have a fan that cools the magnetron and the transformer, a fan above the transformer might work

[@rc1231589]

Heatsink goop under the xformer... uck. In any more than a VERY thin layer, it's not a good heat transfer material. Look for the conformable thermal conductive interface pads, available up to about 3mm thick. Also, why not put a heat sink on top the xformer core?... sticking out the top of the case? As said elsewhere, as the deltaT between xformer temp and ambient increases, dissipation will become more efficient. digikey.com/product-search/en/fans-thermal-management/thermal-pads-sheets

[@champdove24]

Hay are you still around i have Apc.1400 XL I am not able to get in the prog.mode. just keep saying no na need your help

[@McCuneWindandSolar]

Question. how about surge. I see its good for 1500 watts for about 30 minutes what about surge, IE a motor starting that could be over 1500 for a small bit. have you tried to see what it can do with a surge.....Something I'm looking at on my system. I have a Die grinder that is 600 watts and when I hit the switch it shuts it down. and it only pulls about 600 watts when it settles down after motor gets going. I will later look for something I can use to put a good load on it to see what it can do. and see if it took the hack for 1500 watts.

[@knurlgnar24]

This UPS has a good surge capability once modified, and it is far better than most 1500W inverters. My previous videos in this series cover this. I wouldn't expect it to have any trouble at all with any die grinder on the market.

[@McCuneWindandSolar]

***** I was using the tiny 18ah batteries, and realized that it was the batteries, I hooked them to my battery bank and even the one set for 980 watts with no mods fired it up. I have a 1500 watt Heater oil type. that has two settings. 980 would handle 1500 watts for a while before shutting down like maybe 30sec or so. after mods no issue other than the wimpy 10 gauge wire. so that will be the next fix.

[@gerardhandel2870]

You state that the transformer would probably get into a thermal runaway situation. But, this being a 180 Celcius transformer, after half an hour it reached nowhere near that temperature. As higher the temperature gets, the faster the heat dissapation takes places. The more heat the transformer gets rid off in the same amount of time. And then the slope will no longer be linear and gets a less and less increasing slope. It could have been it would have stabilized by itself? .

[@dannyreaves7086]

I watched all 10 videos..Great stuff!! I was going to buy a pure sine wave inverter and some solar panels to recharge a large battery bank for off grid...The question I have for you is this...I have a VERY Large APC Symmetra power array tower! Model # symstrf..The specs are as Follows = Input 200-240v , 80amp, 50-60 hz....Output 120v-,208v-,240v- 60hz...Total output power 80amp, 16kva, 11.2kW...The transformer is the size of a large cantaloupe!! What are your thoughts on converting this to a large inverter? Would I be able to hook up enough battery's to come up with the 200-240v input requirement? Any thoughts, advice? Thanks!

[@Altcapball]

water cooled transformer?

[@duettatraktor7949]

+Brady Rose Water will make the transformer rust butt any type of oil will work. (used motor oil can be used if has ben filterd to gett rid off the metal filings and crap in the old oil) serc "oil filled transformer" on gogle to learn more.

[@Altcapball]

Duett A Traktor lol the water wouldn't contact the iron directly. It would flow through an aluminum heatsink block with sealed channels and valves via tubes and a pumping system like a typical computer cooling rig.

[@duettatraktor7949]

+Brady Rose ok intresting with water so close to electronics. But if computers use it it will probebly be ok.

[@Altcapball]

Duett A Traktor I guess it could be argued that the watercooling on a computer is to cool the chip on a board that is running DC, whereas a transformer has mains AC running through it. However, CNC mills have water cooled motor spindles that run AC mains, and we have on demand water heaters and kettles and such. Water and Electricity don't mix but they can be neighbors in tightly controlled settings. To each his own how much risk you want to consider.

[@AhriMedia]

+Brady Rose my thoughts exactly

[@SylwerDragon]

Well i know it is over that just and idea. Why didn't you move your whole transformer to left side(to old batery compartment. You could put one fan there and it could blow heat from your transformer. No more problem with overheating . Air will be cooler and you can do there what you want termal protection or what ever you want. I really don't know why you didn't do it before :) :) Transformer will be happy and your pcb will be happy also ..less radiated heat..

[@knurlgnar24]

Because it would require another fan and metalwork which I do not claim to be proficient in. :) This seemed like the easiest way. I am sure there are other ways to accomplish the same goal.