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boosting car alternator voltage

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gracc

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Hi everyone,
This being my first post please be gentle.
If I use a 12 volt 100 amp car alternator without rectification and send it through a step up transformer to 144 volts will it be 144 volts at 100 amps or P=VI being 12 x 100=1200 watts/144 volts = 8.33 amps.

Help in definitely appreciated
Thanks.
 
If the 1200W alternator was magical then maybe it can produce 14400W. But its 144V output current will be 8.33A if the transformer is perfect but it will have some losses so the output current will be less than 8.33A.

The alternator has three phases so you need 3 transformers.
 
The alternator has three phases so you need 3 transformers.

Actually with a Zig Zag connection the whole output could be handled as single phase and be stepped up as such.

Also given that common automotive alternators run at higher frequencies a much smaller transformer can handle the power provided the windings are up to handling the currents involved.

What do you need 144 volts for?
 
Thanks for the quick replies everyone,
I'm fiddling around with an old EV and was looking at getting a bit more range by connecting an alternator or 2 off the main drive motor if possible.
Don't know what the drag on it would be, was looking a a brushless alternator thinking it would be less.
 
EV as in electric vehicle? How exactly do you plan to get better range by loading the motor even more?
 
Actually with a Zig Zag connection the whole output could be handled as single phase and be stepped up as such.
...

Hi, can you please provide more info on that, or a link? :)
 
That's right as in electric vehicle.
I was thinking to send the charge from the alternators to the main electric drive motor while in motion of cause, or charge the batteries while travelling.
The EV has 24 x 6 volt lead acid batteries and pulls about 100 amps while cruising on the highway, so if I could at least replace a half of that while driving it would get me to work and back.
Maybe I can get one of them magical alternators as audioguru suggested earlier:rolleyes:
 
I guess magic alternators are your only hope. Simply said, you cannot get more energy out than you put in.
Say your car motor is outputting 15kW in mechanical power, so accouting for losses and imperfections you need for example 16kW from the batteries. Now, lets say you load the motor with an alternator, thus add 5kW load on top the normal load form the ride. So now you need to draw 21.3kW from the battery. Using the same losses for the alternator, it provides 4.7kW to recharge the batteries. Sum it up, 21.3-4.7=16.6kW net load on the batteries. Whoops, adding the alternator-charger cycle, you are all of sudden wasting 1600W more than when you started, and this is not accounting for the additional weight of the alternator and charger etc.
See my point? Losses, losses, losses, and there is no way around that apart from magic.
 
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shhh... don't tell that to the over-unity crowd... they don't like to hear that 4-letter word "loss".... it confuses them.

on a more serious note, the more hardware you add to harvest "wasted" energy, the more losses you incur. in a nutshell, the laws of thermodynamics are:
you can't win
you can't break even
you can't get out of the game
 
An electric car that uses an alternator to charge the battery?
It will work only when the car is coasting down a long steep hill.
 
Hi, can you please provide more info on that, or a link?

It's a common way of spreading a large single phase load over a smaller three phase source.

Basically it's just taking a delta connection and shifting one leg off one way or the other making a sort of Z( /\_ or _/\ ) shaped connection.

If a 120 volt delta setup is converted to a Z connection you get a 240 volt result but at single phase with equal amp draw from each phase.
 
EV as in electric vehicle? How exactly do you plan to get better range by loading the motor even more?

Fine on paper, but 100A when driving will have a fair amount of loss in the cablings. The idea of increasing the voltage to reduce ohmic losses is how the National Grid increase effiency.
 
Fine on paper, but 100A when driving will have a fair amount of loss in the cablings. The idea of increasing the voltage to reduce ohmic losses is how the National Grid increase effiency.
I don´t think I get your point? Yes higher voltage would mean lower I2R losses in the cabling, but not in the "battery->motor->alternator->transformer->another motor or charger or something" way.
 
If the EV's power handling system was designed properly the I2R losses are negligible compared to the total amounts of power being used by the motor.

Say the system is running at 144 VDC and is wired with 30 feet of 0 ga copper cable and has a peak amp draw of 300 amps.

At a warm resistance of .0001 ohms per foot the total line resistance is still only .003 ohms which at some 300 amps still equates to a peak power loss to heating of only 270 watts on a system carrying some 43,200 watts or a loss of roughly .6% of total power being used by the motor.
 
It's a common way of spreading a large single phase load over a smaller three phase source.

Basically it's just taking a delta connection and shifting one leg off one way or the other making a sort of Z( /\_ or _/\ ) shaped connection.

If a 120 volt delta setup is converted to a Z connection you get a 240 volt result but at single phase with equal amp draw from each phase.

If I understand you correctly, you change a 3 phase delta alternator to become 3 phases in series, then use the 3 coils in series to drive an AC load?

I've never tried it, so this is likely a dumb question, but wouldn't the 3 coils and their 3 voltages have significant cancellation?
 
Google shows Zig-Zag connections when the alternator has 12 wires plus the field coil but I think a car alternator has only 6 wires plus the field coil.
 
Why would an electric car need an alternator?
Hee, hee.
To make Perpetual Motion!
Give the electric car a shove to get it going then it will go and charge its battery forever. It might not need a battery if it never stops.

Electrical loss, wind loss and mechanical loss are forgotten.

Never mind using a car that has air and wheel friction, simply connect the shafts and wires of a generator and an electric motor without these losses.
Give the shafts a spin and see if it continues to spin forever or only for a couple of seconds. If it stops then additional power must come from SOMEWHERE to get it going again, over and over.
 
aaahh well I suppose I'll just have to buy more batteries then aye, or maybe a wind mill.
Thought there must be some kind of catch when I hadn't seen it done anywhere.
Thanks ya all for putting me right.
 
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