Alternators, ohms law, electrical theory, limiting factors

[SnowDrifter]

I recall Snafu posting something a while ago in a thread regarding alternator fusing. Went something to the tune of fusing your alt so that the fuse will blow in the event of a regulator going full field and skyrocketing voltage. If amps=V/R, higher voltage across the same internal resistance will yield a higher amperage output.

So then now... Into the alternator side of things. What determines an alternator's power output? Can output be improved with a greater field strength/current?

And the core of my question: If I could find a way to send higher voltage into the rotor, in turn making the magnetic field it produces stronger, is it possible that I could then increase the output of the alternator? Or are there other limiting factors?

[RooTxBeeR]

In for the possibility of wise wisdom.

[Wicks]

I recall Snafu posting something a while ago in a thread regarding alternator fusing. Went something to the tune of fusing your alt so that the fuse will blow in the event of a regulator going full field and skyrocketing voltage. If amps=V/R, higher voltage across the same internal resistance will yield a higher amperage output.

So then now... Into the alternator side of things. What determines an alternator's power output? Can output be improved with a greater field strength/current?

And the core of my question: If I could find a way to send higher voltage into the rotor, in turn making the magnetic field it produces stronger, is it possible that I could then increase the output of the alternator? Or are there other limiting factors?

I'm no alternator guru so I hope Tony D or one of the alternator companies chime in, but I'll toss out my 2 cents.

Q1:

I remember reading this post as well.

Fuses are thermal devices. They blow from excessive heat caused from high electrical currents. They won't blow from high voltages alone, you'd need a circuit breaker for that.

Given that you have regulated power supplies on your equipment, the higher the supplied voltage, the current will actually go down, not up.

That is if everything is working properly. If the voltage spikes high enough to cause damage then its hard to determine what will happen.

The current drawn from an alternator really depends on the load applied to it from your equipment.

Just because the alternator is outputting more voltage doesn't mean it will "push" more current automatically.

Its certainly possible with constant resistive loads but it depends on the equipment.

Q2:

Alternator output is controlled by field current and RPM. You need the field current to produce the output and you need the rotor spinning to provide the alternating current necessary to produce power at the output. The faster the rotor spins, the higher the frequency of the output and thusly the available current at the output.

The regulator is there to keep everything in check.

Given for a specific alternator, it can only be spun so fast and can only handle so much field current so there will be physical limits.

Q3:

I would think so, yes. Most modern factory alternators are PCM or PWM controlled.

Therefore a pulsed signal is applied to the field winding. The higher the duty cycle of the signal, the higher the resulting voltage and therefore more output.

I'm sure there are limits before potentially physically damaging any of the circuitry.

Probly a good question for the alternator makers as far as how much field voltage/current they recommend.

Of course I'd assume if you start asking questions like these, the alternator manufacturers will instantly state that your warranty is now VOID

[Smoove]

I know when the internal voltage regulator went out on my alt, having fusing probably would have saved my battery. My optima was blowing bubbles when my 200amp alt started doing 18.5v. Yes, everything in the truck was turning on and off. Now I am fused at 225

[Wicks]

I know when the internal voltage regulator went out on my alt, having fusing probably would have saved my battery. My optima was blowing bubbles when my 200amp alt started doing 18.5v. Yes, everything in the truck was turning on and off. Now I am fused at 225

How would a fuse help?

A fuse is simply a chunk of wire which doesn't know the difference between 14V and 18V.

Was the battery pulling excessively high currents at the elevated voltage?

[Smoove]

I know when the internal voltage regulator went out on my alt, having fusing probably would have saved my battery. My optima was blowing bubbles when my 200amp alt started doing 18.5v. Yes, everything in the truck was turning on and off. Now I am fused at 225

How would a fuse help?

A fuse is simply a chunk of wire which doesn't know the difference between 14V and 18V.

Was the battery pulling excessively high currents at the elevated voltage?

Wont the increased voltage increase the amps? If it wont than my fusing is useless.

[Wicks]

I know when the internal voltage regulator went out on my alt, having fusing probably would have saved my battery. My optima was blowing bubbles when my 200amp alt started doing 18.5v. Yes, everything in the truck was turning on and off. Now I am fused at 225

How would a fuse help?

A fuse is simply a chunk of wire which doesn't know the difference between 14V and 18V.

Was the battery pulling excessively high currents at the elevated voltage?

Wont the increased voltage increase the amps? If it wont than my fusing is useless.

I wouldn't think that increasing the voltage on a battery by a few volts would drastically increase the current into it, but that would have to be confirmed.

Regardless that 18V alone won't blow the fuse.

[Smoove]

First of all. Are we the only ones still up????

Second, I thought it was cool as hell seeing the optima blowing bubbles. I started the truck back up when it managed to get me home just to meter it.

[audiofanaticz]

Normally an increase of voltage results in a decrease of amperage needed to said device being powered.

[Smoove]

Well shit. There is a waste of fusing.