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Forum Index : Electronics : hi volt batt inverter?
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| adelaide Regular Member  Joined: 24/03/2006 Location: AustraliaPosts: 46 |
bit above my head but think it is possible ,
help to make progres or radio and vitamin b |
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| RossW Guru  Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Higher battery voltage means lower currents for the same power. "I-squared-R" losses are just that - the square of the current, times the resistance, so if you can halve your current, you reduce the losses to a quarter. Transformers have losses (various losses - I^2R as well as magnetic losses) but they do have a couple of beneficial side-effects including their energy "storage" for short-term transients. The drive circuitry for high voltages is trickier, and the high voltage, high current devices are more expensive and more difficult to get, but in theory you should be able to create a transformer-less sinewave inverter with a "H-bridge". You'd probably need a decent choke to reduce the high-frequency switching components in the output, but I think it would be worth a play! (BTW, your "240V AC" household power is 240V "RMS" - close to 340 volts peak to peak) |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
hi Adelaide Other day I wrote about almost same as you however my idea is about using sealed Nickel-Metal Hydride from Wrecking Toyota Prius that product 273.6 volt DC and wonder if able to change to 240 volts AC by specialilty made invertor plus using F&P windmill to charge the batteries however l do not know how many amps putout on Toyota Prius batteries ? so has anyone have thought about it ?? Anyway l am still waiting for anyone who able give adivse ??? Dwyer the bushman |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5036 |
Adding to what Ross said, to get 240VAC you would need a battery supply of 340V DC. If I remember my AC theory ( was a long time ago ), the 240VAC has the same "Power" as 240VDC, BUT its actually a 340VAC peak to peak sine wave ( correct me if I'm wrong Ross ). So you would need to feed a 340VDC supply into the H bridge. If you rectify and filter 240VAC, you end up with 340VDC. But all that aside, if you had a 300 Plus battery bank, then you could build a H-Bridge and 50Hz modified sineware oscillator to make 240VAC. I have a small UPS thats works that way. Instead of a large step up transformer operating at 50 Hz, it uses a small switchmode power supply to generate 340vDC from the 12v battery, an then has a H-bridge to convert this to 240AC. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| adelaide Regular Member Joined: 24/03/2006 Location: AustraliaPosts: 46 |
not shore about voltage i would need but would it be 240 1 way then next Hz 240 other ? also i may need v reg circuit cos charging v would be hi and lo bat lower ? advantage would not need to rewire some fp starters hahah , could make a dc earth leakage protect out of sensitive fet and latching relay. with the prias bat bank could u salvage the rest and make a car?I'm weighting for my other car to be finished then making my first elec car have bat/motor 50 x50a fets to parallel. keep the ideas coming Ty help to make progres or radio and vitamin b |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
A qualified "yes". 240V AC is *usually* interpreted in this context as "240V RMS" (Root Mean Squared). In a perfectly sinusoidal waveform, that would be 340V P-P (Peak to Peak). If you applied 240V RMS to a light globe, and 240V DC to an identical globe, they would appear to be equally bright. Not all "AC" is equal though. For example, a "quasi-wave" or
"modified square wave" inverter may produce 240V RMS with a very
different peak to peak voltage. Most of these things can have a VERY
high peak voltage when batteries are full, but reduce the pulse width
to keep the RMS right. I've seen 400V and over! However, when the
batteries are low, they often make barely 250V p-p and have very long
pulse widths (almost the entire half-cycle) just to keep the average
up. This is what makes them so deadly with sensitive equipment. Again, "sometimes". Full-wave rectifiers will, half-wave won't (unless it has virtually no load at all). Its (sole) upside is that it's more efficient. If running incandescent lights or heaters, it's probably ok. If running anything else, don't. If trying to "synthesise" a 240V supply from a high voltage DC supply, the only reasonable way to do it (in my opinion) would be to use a proper PWM (pulse-width modulation) device (there is dedicated hardware to do it, or a PIC could probably do it easily). There are really only 3 states you need. * Top left/bottom right 'H' bridge pair on (others off) * all bridge drivers off * Bottom left/top right 'H' bridge pair on (others off) By quickly (at least 3KHz, preferably >10KHz) chopping one pair on and off and varying the on:off ratio, you can synthesise a fairly reasonable sine-wave going from zero gradually up to full output and back down again. Then, by leaving that pair off and switching the other pair the same way, you can create the opposite half wave. The resulting 50Hz output will have all that 3KHz switching noise still present, so some filtering will be required. Easiest is just a choke or inductor in series (which will try to resist "rapid changes" and acts to "even out" the supply). This is where the higher switching frequency is an advantage - smaller chokes will do the same job (or conversely, the same size choke will do a better job). Downside with higher switching frequencies is the lower efficiency of the power switching devices (T-FET, MOS-FET, whatever you use). The other thing I forgot to mention, but will now, is the downside of massive series-connected cells. If you get any variation at all (which is almost inevitable), you end up giving that cell a really hard time. Eg, if one becomes slightly high resistance, there is suddenly a much higher voltage drop across that cell, meaning more heat, and it all gets worse. When finally, that cell fails, your whole string fails. Upside is that you can bypass a single cell fairly easily in a high voltage string because it makes little difference. There are also some nifty "charge shifters" I've seen for large series strings, where one of these devices is connected across each cell, and the next cell in the string. It can "move" charge from one cell to the next one to "balance" the charge. It can do this while charging and/or discharging. Sounds nice in theory, haven't tried/seen it in practice. RossW |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
Hi Ross somtime ago l got a quote on engine governer Wardwood (AUST)Apecs 500 with other kits cost nearly AU $850 and l near fall off my chair so l contact Wardwood Dealer in USA got back as suprise me only half the cost regrettabie they cant sell Woodward kits does not allow them to ship outside the US. They protect their other factories for competition. outside of USA So can you able give me the cost when you brought it as l hope not to be rude just need some ideas thank ian Dwyer the bushman |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Yeah, it was moderately expensive. The 500 was the one I got - and although the electronics was fairly cheap (about $150 I think), the really expensive bit was the linear actuator! I got 4 items from them - the APECS-500 unit itself, one of the linear actuators (I don't recall which one it was now, the one with the lightest spring from memory), one of the long-thread magnetic pickups (that mounts right up by the ring-gear (in my case, 112 teeth so 112 pulses per revolution of the engine)), and a linkage kit (which has two very nice rose-couplings and a threaded rod). Subsequently, I had to then get the software because the thing is NOT as advertised just a "dumb box" that you give power to, RPM signals, and it controls the actuator. It's a whole lot smarter than that, and tries to do engine warmup, cranking control etc which I didn't need (or want) because my electronics already had all that! Given my time again, I think I'd do it all differently. Don't get me wrong, it's a nice box of tricks, built well but overkill for what I need, and perhaps as a result of its complexity, doesn't work as well as I'd like. My genset is also probably a little more complex than necessary - it's a standard 4-cylinder 1800cc petrol engine from a ford laser (engine is actually made by mazda). I've pulled off all the fuel injection stuff because I'm never going to run it on petrol. Instead, I've added a regulator and mixer and run it off the 500Kg LPG cylinder that runs the house. I also have a small stepper-motor operated valve in the low pressure gas line between the regulator and the mixer, and that is controlled by the output of the Oxygen sensor in the exhaust. Because of the run-time of this thing, and for environmental concern, I want to run it as efficiently as possible. So regardless of the output load, I run the air/fuel mix at optimum by adjusting it constantly. Unfortunately, my load varies (the inverter/charger pulls varying amounts of current, and loads in the house vary as things tun on and off (the microwave oven is particularly bad in this regard - much worse than the washing machine or dishwasher!), so between the change in load affecting the engine RPM, and the fuel controller adjusting things (and changing RPM), the poor old governor is working pretty darn hard to keep engine revs constant. Under "steady state" (ie, no change in load), the lambda controller (air/fuel ratio) is still hunting from rich to lean all the time (I plan to replace the narrowband O2 sensor with a wideband one), the governor is keeping engine RPM sufficiently constant that the output frequency is only varying from 50Hz by about 0.1Hz which is pretty good. The gearing is such that for 50Hz the engine is running at about 1889 RPM. Alas, under varying loads (from almost nothing to about 75% full load) the thing hunts from about 49.5 to 50.7Hz which I'm not too happy with. It *SEEMS* that the woodward controller is too heavily damped, although this is something that seems to have changed over time. It used to be much better, but was too "twitchy" when cold and would constantly over-rev then under-rev until it got warm - taking anything up to 2 minutes. It settles down now in about 10 seconds after "throttle-up", but is sluggish to adapt to changes. So far, I replaced the spark plugs after about 1100 hours of running and they were still in great condition. I nearly put them back in, but as I had new ones there, I changed them anyway. I do an oil-change about every 400 to 500 hours. It gets a little dark, but it still feels and smells good. It doesn't get "sticky" like so many other engines have. Running on LPG seems to agree with it at least :) I'll post some photos if you're interested? |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
Hi Ross Thanks for information as l do agree with you about warming the motor for fews min untill they get hot they run normal anyway l will try to get Woodward kit overseas and l have spoken a guy who is toolmaker at workplace and told me that he have brother working in England and might able to get me one and l didnt have full detail about Woodward with me so l will try see him later during the week as l only work partime . my toyota engine is 4k and l have to modify the camshaft to increase torque at low rpm as motor torque come around 4000rpm is not good enought dont need that 3000 rpm that all l need however my biggest mistake that l should brought industrial volkwagen motor with governor for $500 on E-bay brand new few week ago and l didnt think faster enought It gone now and other day l made a visit to foundries about getting alloy hubs speciality made for F&P windmill and hoping will give me the cost this week or l will fabication myself as it not to hard to make and l will post a photo of my homemade 10 kva 3ph gen tomorrow and would like to see yours as well ian |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
20-20 hindsight hey! Sheesh, 4000 RPM is quick if you plan to run the thing for extended times. That's why I wanted to run mine down around 2K. Ok, sorry for the long post.... but here goes. Looking at the engine and alternator from the shaft end (I suppose the "back" of the engine). The shaft (and therefore, alternator) both rotate counterclockwise when viewed from here. The belt is a large timing belt, the two "idler" wheels are just to stop the (quite long) belt from slapping. 
The frame with alternator fitted and engine sitting, ready to be lifted into position. 
The speed-sensor (at about 10-oclock position) close to the ring-gear. 
The whole thing more-or-less as it is now, although I have simplified the cooling system pipework considerably now. Heat-exchanger for the exhaust is on the left. 
The linear actuator and coupling: 
(and from the side and above): 
There are any number of other photos... if there's anythig specific, let me know and I'll dig 'em out! RossW. |
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Trev Guru Joined: 15/07/2006 Location: AustraliaPosts: 639 |
Hey Dwyer, I plan to look at casting aluminium hubs for the F&P sometime. We have been discussing the idea on the forum General windmill chat - Another F&P windmill builder. My Business card is also there. Cheers Trev @ drivebynature.com |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
Hi Trev Yes that l have been working on F& P aluminium hubs for some time and is halfway at the moment however problem is large flywheel press that l save and brought the 20 tons press from scrap metal getting chop off to pieces and my friend who own scrap metal yard brought down to my place and got it cover up from the weather last year until couple months ago l start to make press tooling to make aluminium hubs and found out the flywheel press only have max 25mm stroke which is good for sheet metal l need 60 mm stroke would be better I didn’t look at the first place anyway l am now building high speed hydraulic press and is halfway building and aluminium hubs will be part pressing, fabrication ,welding and machine down and hoping will be ready in few months time depend on my heath When is ready I will show it you all as l did made some enquire about in casting at Toowoomba it was too expensive for average person pocket Trev maybe you should try make in casting as l haven’t not work out the cost casting or fabication which is cheaper ?? let me know so we will share some ideas . 
Dwyer that bushman |
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