Voltage question

From this distance, and not knowing the type of generator/alternator you have selected, it is difficult to be specific.

However, the principles are clear. In an electric motor, torque is proportional to current and speed is proportional to voltage. The same applies to a generator, so if you need to increase voltage by a factor of 4, you need to increase the shaft speed by a factor of 4. You could do this with a gearbox or with a cogged belt.

Alternately, you could use a DC to DC converter that would output 200V DC to the grid tie inverter you have chosen. It could be designed to operate over an input voltage range of 24 to 48 volts, providing additional battery charging that would not be provided by a fixed gearbox.

HAVE FUN

The alternator you have could be modified by bringing out the three windings separately.Three bridge rectifiers, could then be connected, one to each winding, and their DC outputs connected in series. This will be worth a try if the alternator was delta connected, but less likely if star. You could wind, or buy, three (single phase) auto transformers to give adequate voltage to an appropriate rectifier.

You could alternatively collect discarded power supplies from personal computers and extract their 200V working mains rectifier electrolytic capicitors(you could buy new but recycling scrap is so much more worthy!). In the power supplies they are connected to "volt double" 117V inputs. If you volt double all your three windings and connect their DC outputs in series, you will have over the 200V for your suggested inverters. The six diodes and required capacity will depend on the altrrnator's power, rpm/ Hz, and if star or delta connected before winding separation.

My solar cells feed a nominal 48V to an Australian made "Latronics" grid connected inverter. I doubt that it has worldwide certification but it might be acceptable.

THe DC DC converter I feel is better choice. However I am not sure why the line tied inverters can not invert from the 24V.

Got it you are outputting 250A @24V for the 6KW power. I feel this is too much current.

Better way is to transform the Votlage at the alternator outlet to high AC say 600V , rectify to DC then invert it ?

There are a few US companies that make an export model inverter which is grid-tie and uses a nominal 12/24/48VDC input. I'd try Outback Power Systems. I think you'll need a battery bank to ballast the incoming current and a diversion load controller to dump excess current.

Greetings miik999 ,

Whatever solutions we could suggest here on this forum will be overshadowed by the requirements of the grid owners.

Your local power supply company probably has a great deal of specific information on how and what is required to connect to their grid, and it's free for the asking.

If you plan to grid connect on the sly, we can't help you - it's simply dangerous and probably illegal, but mostly foolish since the grid owner will be happy to help guide you free if you just ask.

Regards, CJM

The original poster could theoretically kill a lineman if its not done correctly, or more likely blow up your equipment......

As You said, its simply not worth trying to do it wrongly......you won't get paid your money for the power for an illegal system either.....

I have heard that in some countries the equipment is not cheap though.....

Mr Germany,

If your ref to the original poster is to jcrock, let me clarify. I agree with you that 200V DC can kill a lineman. However I did not suggest connecting that to anything other than the "grid tie inverter" of choice. I presumed when I wrote that, and I am clarifying it here, that the chosen "grid tie inverter" would be one with technology fully approved by the local utility.

Thanks for the opportunity to clarify. I have spent my 40+ year career seeking to make possible the safe and healthful use of hazardous processes and hazardous materials. I'd hate to deviate from that now.

JC ROCK

It is amazing to me how some (overly?) sensitive people on CR4 react to a possible criticism, that I might add here for clarity "WAS NOT MADE NOR INTENDED!".......

I was actually only AGREEING with another poster (which was I replied/linked to him and him ONLY) and adding a few extra comments to his already (to my mind at least!) correct answer.

Either you cannot read English, or you cannot understand it properly, and can only write it!!!!

I personally cannot see the connection between my post and yours at all. If there, its pretty far fetched, maybe you are aware of something I am not?

Please understand, nothing I wrote was aimed at you personally, therefore its all in your imagination only......

Stop being petty and overly sensitive, it will help you considerably further in this life........

WAW !!! (A Very British comment!!)

There is also a US comment that partially escapes me "What a (**)ROCK of shit!"

since you are working at 24V and 6KW, the current is quite high on DC side it is 6000/24 = 250A.

All the costs will go up at this amperes (conductors, diodes, etc all have to take care of the current). However even if you use a 220 V, it is only 27A , and no specific over insulation is necessary.

As far as safety is concerned, you are going to work in high voltage any way at the inverter level (for feeding to the grid)

so

a) Either you work in 24VAC/144A 3 ph -> 24VAC/250A DC(rectifier) -> Reqd DC (DC-DC Converter) -> Line commutated inverter -> grid

b) 24VAC/144A 3 ph -> Rectifier(24VAC/250A DC)-> (Line commutated inverter) 24V AC -> transformer (grid V to 24V step up)-> grid

c) 24VAC/144A 3 ph -> transformer (24VAC-> reqd HV) -> Line commutated inverter -> grid

The underlined area is the low V (hence safe) but high current hence costly.

the transformer + rectifier+ Inverter can be made as a single module.

Only problem as far as I can see is the charging of batteries in case you don't want to off load all the power to the grid and want to save some in the batteries but then why ?

Thanks SB Have you any experience with Axial Flux Generators ?.

I can wind the coils to produce higher voltage but there would be a limit which I dont know yet.

What way would you tackle the situation. Would you send the max allowed back to the grid and store the balance ,if any, in batteries.

If you were to do this how would you split the power between the inverter and the batteries. Would 2 inverters be needed or could the battery power be inverted by the same inverter.

I am sorry, no relation with these. I am only in MW generators that also in 100s.

What I am commenting on is from my long ago Electrical Engg knowledge (Esp power electronics, my major in MTech- MS for you)

There is no use of rewinding when a simple transformer can step up at a cheaper cost, provided the frequency is not very low. You can have the number of poles in your gen to have an acceptable frequency (lower frequency will make the transformer not work properly)

If the line commutated inverters are used, there will not be any balance, (however will your electricity supplier pay for your feed-back ?)

The one way (if you are storing for your rainy day- we have power cuts, but you don't have them- at least thats what people say) is to store at 24V stage, then use a normal inverter (line commutated not bnecessary, since there is no line) to light your home. The rest can be fed to the grid. That way you are independant of the grid as far as your home lighting is concerned.

ie

Gen-> rectifier (24V DC)-> battery-> Inverter -> Home

-> transformer-> rectifier-> line commutated inverter-> leftout power to grid

(free of cost ? )

BTW another link is active on Feeding the Grid.

Hi there

I'm not sure what the specs are on the Irish grid, but if this was a set-up for the US, I'd have a pair of 3.5kVA inverters (Outback GFX3524) a MX-60 charge/load controller (or other suitable diversion load controller) and as many L-16H (6 V) batteries as I could afford (minimum 4). This would give me 3.5 kVA @ 240VAC or 7kVA @120VAC with a grid-tie and a back storage bank for when the grid goes down, and, where I live, it will go down. Series/Parallel inverters can be fed by two 125amp feeds instead of 250 amps. The more you step up/down the current the less efficient the system is.

Chris

PS I set up small off-grid/grid-tie systems for a living.

If your grid is ready to accept the power and pay for it, why will it be stupid ?

(If you pay back 6KW to grid and draw the same you gain 3cents/KW is it like a PMM ? )

Any way lighter side aside. I feel you have a running idea- with a load controller, you can divert to charge the batteries, but check the amount of battery bank required.

If you have a 10KW gen, and based on the wind condition (that you must know), the average load- generation should balance out in the way

Average Load - Average use <= 6KW

Also (Max generation-6KW) has to be matched by the battery bank. The battery bank can be used only to smoothen the power flow (like an electrical fly wheel) to avoid overcharging it.

I don't see technical infeasibility, but I don't know the commercial part.

Not stupid at all. The systems I set up essentially prioritize the battery bank and then the grid. When the batteries reach bulk charge the excess is "dumped" to the grid. If the grid is down, you have a diversion load to take the excess, ie H2O heater. The inverters can be set for the amount to sell back, etc....

Here the utility will only cancel your power usage, not pay out.