Alternator Q: DC Output of 84V & 300A?

[-Rane-]

Hi, I have a rather weird question to ask.

I'm in need of an alternator that will give me a DC output of around 84v (maybe more) and 300 amps (more or less). To my knowledge, no such alternator exists. Not even a $3000 alternator will do it (and I'm not willing to pay that much anyway). So, I'm forced to come up with a more creative solution.

I've seen that some car audio guys will put a series of alternators in their cars to account for the mass of electricity they're using. Am I right in assuming that if I just wire the outputs of a few alternators together, the volts and amps will increase in a in a simple "1+1=2" fashion?

Thanks!

 

[Mech_Engineer]

That's a 25 kW alternator, some pretty serious power. You're going to have to look into generators in that range to see how they generate power, my guess is you'll probably have to get some sort of generator that supports that kind of power and then convert to the voltage you're looking for.

 

[FredGarvin]

What alternator puts out a DC voltage? You're going to need a rectifier which means that you will incur some slight losses. Still, that 25kW number is pretty big.

Have you looked into industrial power supplies? Then again, if you're not willing to sign up for $3k, then that probably won't be a viable option either.

 

[minger]

What alternator puts out a DC voltage?

Indeed, alternator of course short for Alternating Current Generator (ACG).

 

[Mech_Engineer]

What alternator puts out a DC voltage? You're going to need a rectifier which means that you will incur some slight losses.

Indeed, alternator of course short for Alternating Current Generator (ACG).

In automotive applications, a diode is used which "block" the negative portion of the alternating voltage, approximating a DC voltage.

A/C voltage is of little use in a D/C system, such as used in an automobile, so it has to be converted to D/C before it can be used. This conversion to D/C takes place in the "output diodes" and in the "diode trio." Diodes have the property of allowing current to flow in only one direction, while blocking current flow in the other direction. The output diodes consist of six diodes, one pair for each winding. One of the pair is for the negative half cycle, and the other for the positive half cycle. As a result of this diode rectification, the output of the alternator looks as shown in figure 4.

Surprisingly enough, the output of the alternator is not a pure D/C as one might expect, but a pulsating D/C. Because there are three windings, each with a positive and a negative half, by the time the voltage is passed through the diodes, there are six pulsations for each rotation of the rotor. This is close enough to D/C for most automotive components. Critical components, such as radios, have their own internal filtering circuits to further smooth out the waveform to a purer D/C.

 

[stewartcs]

In automotive applications, a diode is used which "block" the negative portion of the alternating voltage, approximating a DC voltage.

That's what Fred and Minger are referring to (rectifiers use diodes).

CS

 

[kv_home]

25kW is 33hp, neglecting any losses - that's a lot of power, and can be very dangerous, what are you trying to do? Is this paper excercise or are yuo trying to build something?

You say alternatior which implies you have a motor already in place, from which you are going to draw power - this linkage must support >33hp, and the motor must have excess capacity to support the power consumption

Another option is buying DC power supplies - many off the shelf power supplies are available to give voltage and current you are looking for. (still cost $$$$)

 

[kv_home]

original question - as to stacking alternators together - the voltage and current do not add in a 1+1=2 fashion.
For any power supply

Wire them in parallel and you get the current going up as 1+1=2, but th evoltage stays the same

Wire them in series it flips, voltage goes 1+1=2, current stays the same.

This si because total power for each supply stays the same
V*I=P, and 2 supplies and you double the power, if you double both the voltage and the current that requires 4x the power.

This is a vast oversimplification - not all supplies can be stacked in this fashion safely, you must know what you are doing