Alternator needs battery power to generate power?

[dom14]

Hi Guys,

I've been wondering(again).

I'm onto a little garage project of combining an old mower motor with an alternator to make a simple generator.

It is that i'm bit confused with the idea in the heading of this thread.

1)Do I need to connect a 12V battery to the alternator exciter(or field wire/trigger wire) OR

2)Can I simply join the field/trigger wire to the B+ and that should do the job?!!

3)How do I use the sense wire? Do I need to join that to the B+ as well(when there's no load present)?

Thanx in advance for any advice/tips/explanations.

[LostBenji]

A small battery to provide exciter power to get the field energised, after running and producing power then it could be run standalone but regulation will be shit. Use a battery on it (just a little mower battery is fine) and run the sense wire to the Battery + terminal. Ground or chassis to the - terminal.

[Yendor]

Whats the generator going to be used for?

[dom14]

A small battery to provide exciter power to get the field energised, after running and producing power then it could be run standalone but regulation will be shit. Use a battery on it (just a little mower battery is fine) and run the sense wire to the Battery + terminal. Ground or chassis to the - terminal.

Thanx mate. If I understood you correctly, without the battery, it won't be possible to excite the field coil, and
battery is also necessary for the ongoing voltage regulation as well?

It's not possible to use the alternator as generator(12V or so) without a battery?

Thanx

[dom14]

Whats the generator going to be used for?

I'm thinking to run 12V appliances or combined with an inverter to run mains appliances, and of course on rare occasions to charge a battery as well.

I imagined it might do lot better than my measly little generator?

[Yendor]

If your going to run accessories you will need to fit a battery, so you might as well make it a decent size one.

The alternator might self excite but you will need to find the sweet spot in the RPM. This could be a bit hit and miss so I would recommend connecting up the exciter/warning light circuit. You can just connect this to positive (no warning light) but I would use a warning light. If you do just connect it to positive it will still need to be via a switch or it will flatten the battery when the alternator is not running.

Just connect the sense wire to the B+ terminal on the back of the alternator.

[mudnut]

An old style twelve volt generator will have more chance of "self excitation", but a battery would still be needed to give proper voltage regulation as well.

[dom14]

If your going to run accessories you will need to fit a battery, so you might as well make it a decent size one.

The alternator might self excite but you will need to find the sweet spot in the RPM. This could be a bit hit and miss so I would recommend connecting up the exciter/warning light circuit. You can just connect this to positive (no warning light) but I would use a warning light. If you do just connect it to positive it will still need to be via a switch or it will flatten the battery when the alternator is not running.

Just connect the sense wire to the B+ terminal on the back of the alternator.

Thanx mate..but..

Alternator stator winding need the field winding(magnet) to generate electricity out of the stator winding.
Then without a battery to initially turn the field winding into a magnet it apparently won't work?
But, once the stator winding started generating electricity, it can feedback to the field winding and feed each other?

So, it it essential to have a battery connected to the field winding, at least for a fraction of a second to generate electricity out of the stator winding?

Does it work in theory?! I mean like chicken or the egg first sort of situation(which obviously I don't have to understand, but would love to ).
Is possible by wiring up an alternator to self excite by connecting the trigger wire to B+?!!
If I understood you correctly above, it's possible, provided I work out the proper RPM spot for that by experimenting?

I understand that without a battery, alternator B+ output voltage won't be smooth(battery function as a capacitor to smooth the alternator's pulsed DC output?).
So, if I'm to use an inverter, it would be a good idea to make alternator's output is smooth by connecting a battery to B+?!!
And that would also apply to many 12V appliances as well.

The only issue with using a decent size battery in the unit is that it would make it heavy. But, of course, the battery doesn't need
to be attached/fitted to the generator.

[mudnut]

You could use a small pony alternator that uses permanent magnets to give an initial start up. I have tried running alternators on a bench test, but I had to flash start the field.

[dom14]

An old style twelve volt generator will have more chance of "self excitation", but a battery would still be needed to give proper voltage regulation as well.

Yes, I think you answered my question on the previous post by the above answer.

It's pretty obvious I need a battery connected to make the generator a useful thing for 12V appliances or mains appliances via an inverter, as you explained.

My physics head can't get around the process of "self excitation".

If the stator winding can't generate electricity without the field winding's rotating magnet, where on earth does the stator winding
generate the initial electricity to power up the field winding??!!

I can't get my head around that!!!

What comes first, chicken or the egg?