easy way to generate an ac signal

The excitation current is carried on the rotor via the slip rings. The generated current is taken from the yoke,

So do we still think a flat or open circuit battery draws excessive currents?..

There are various sorts of brushless motor. But they all run on AC.

So you admit that the rotating part of a motor doesn't *have* to carry AC, then?

Harry , Yes but is it AC or DC ?...

In a moment he'll be claiming that the rest of the universe is rotating around the rotor so he's still right. :-)

But he still has not answered my post about ball-bearing motor being pure DC.

But not in the rotating part harry.

Clueless C*ut

I am now. I had a notion you were in Oz, but that's the other Tony.

However, I was brought up with UK/French/German/Italian and US electrics, much to my horror.

Sigh. How many times do you have to be told that if a battery is 'totally' flat to the point were it allows an alternator voltage to go dangerously high, it won't take any charge at all in a few minutes. The reason it has gone high impedance is it's sulphated. The only way to attempt to reverse this is with a long slow high voltage charge. Over several days.

Of course not. Where did I say it did? Virtually all alternators have the AC part in the stator. The rotor is just a (multi polar)(electro) magnet.

Virtually all "DC machines" are the other way about (ie the stator/ yoke is the magnet) so that the mechanical rectifier/inverter/ commutator can function. The AC is of course in the rotating bit.

Yes I have. It is not rotating. Read upon:-

The excitation current in the rotor is DC. The AC is in the stator. This is for the simple practical reason that the excitation current is a tiny fraction of the generated current so the slip rings and brushes and rotor can be smaller. There is no theoretical reason why it should not be the other way about.

The only reason there is an excitation current at all (as opposed to a permanent magnet) is that by controlling it, we can control the voltage output from the alternator.

Very large traditional alternators have a excitation generator (DC machine) on the end of the alternator shaft. Some even have a pilot excitor on the end of that (for the main excitor) So by controlling a current of a few amps the output of the alternator which might be several Mw can be controlled.

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Yes you did.

Harry when in a pit stop digging!...

You said above,

The rotor in a car alternator carry's or is excited rather with DC..

The stator has an alternating current induced in it which is rectified to DC...

Well you got that bit correct!..

You might be confused with what an alternator rotor produces due to its pole pieces being arranged as they are 'tho...

Read this...

You are the ignorant half-wit. The *motor* runs from DC.

MBQ

Inverter drives for brushles DC motors do not generate sine waves either. Simple ones use PWM to approximate them. More complex ones use

Harry likes to take a evry simplistic view of the world.

MBQ

The machine as a whole can be driven by DC, that's even easier for most people to remember.

Do you need it explaining to you?

MBQ

A switched reluctance motor is a DC motor.

MBQ