Field inductance of automotive alternator rotor

Why not just measure it ? Got a function generator that can put out a sine wave and a one ohm resistor ? Two pi F L.

Also, though they are probably all pretty close because what works best is what works best, they probably vary some, so trying to be accurate might be futile.

And out of curiosity, why do you need to know this ?

Off the top o my head I think you'll find one in a luxury car to have more inductance but probably about the same DC resistance, and an economy car le ss so but still about the same DC resistance. Just a guess but it makes sen se.

Alternators in cars have gotten cheap. This to the point if you put a dead battery in one and jumpstart it the alternator is overloaded. The old alter nators would slow down the idle of a 400 HP engine when the jumper cables w ent on to jumpstart another car. Now, simply don't give anyone a jump in th ese newer cars.

This is progress.

You're making shit up, even a dead short won't harm an altenator.

they are inherently current limited.

The alternator is some miles away, or I would try and measure it.

Alternators are generally current limited by design, so I'm a bit surprised at your assertion they can be overloaded.

I just want a ball park figure.

And they come in different current ratings. 100A alternators are easy to get; I suspect that RV or big-rig sources would have even heftier units to play with.

I think you need to just measure some -- and if you're going to be switching the voltage on and off to modulate the current, pay attention to losses as well.

You trying to figure out how fast you can make one change field current?

Seems VERY low. A big spool of wire in an iron "bobbin" ought to have a lot more inductance than that. I'd expect many mH. It may also go way up when the rotor is installed in the stator, completing the magnetic circuit.

Jon

From my alternator regulator designs of the mid '60's I recall inductance of around 5mH and 2.4 Ohms. ...Jim Thompson

the rotor is solid iron, so that's a shorted turn coupled to the field coil, that's going to reduce inductance (W.R.T. laminated iron).

We are talking about a nominally DC field so we shouldn't be concerned about short a circuit turn that only have meaning when excited by AC.

The stored energy will be independent of a short circuit turn and should depend on current, the number of turns and permeability.

I will concede that stamped laminations have iron grains that are stretched and consequently have isotropic permeability. Thankfully highest in the direction of interest.