Alternators, ohms law, electrical theory, limiting factors

[revoracing247]

increase in voltage with the same resistance though will increase amperage. like snow said, amps = volts/resistance. so if you raise voltage then you can see how the amps would increase.

wicks sounds like he knows more then me about alts lol but yeah if an increase in the voltage in the field causes more magnetic flux then it should create more power on the coils spinning through it. but the PWM signal sent to the field and the rectifier and the physical limits have an important factor into the amount of output the alt can have.

how were planning on sending the feild a higher voltage anyways? cause i mean unless they have a voltage regulator on the input to the feild isn't the feild being sent what ever voltage the alt is outputting? i.e. when it first starts it's 12v from the batteries but ones its running the field has 14v?

idk it's still morning ish and i can't think

[Dwn4BassAlan]

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?

It's 2:30 am new years day, I'm not fully in the state of mind I need to be to answer this thoroughly, but I'll put something in until I can really put it all down later.

A big point I would advise to remember is that as it heats up, resistance will increase, therefore output will decrease. Nothing new of course, but I think that is kind of key to figuring out ways to approach the questions you asked, especially the last one. Like mentioned above, if voltage increases with the same resistance then of course output will be higher, since (P= V x I) but since the alternator will change as it warms up and depending on the conditions the car is in, it will keep changing.

As far as what determines it's output, that's all in the design: take the DC alts for example:

The SPX on top is a 3 Phase unit which makes it less efficient at producing power along with it having a higher AC ripple current (engine noise) due to it only being a 3 phase unit. (This is why the SPX is cheaper than the XP even though it produces more output than the XP). Due to it being a non-hairpin stator it loses up to 30% of its peak performance when it's introduced into extreme heat.

The XP in the middle is a 6 phase hairpin stator. This alternator features square wire and produces over 200% less noise than the SPX alternator due to the stator design. This alternator is the most efficient alternator on the market due to the hairpin design which allows for less mechanical energy to turn versus a conventional non-hairpin stator. Due to it being a hairpin stator it loses up to 15% less of its peak performance when it's introduced into extreme heat.

The SPX-i on the bottom is a 6 phase stator. This alternator produces a little more noise than the XP, but significantly less noise than the SPX due to it's 6 phase design. This alternator produces higher output than the XP. However, being a non-hairpin stator it loses up to 30% of its peak performance when it's introduced into extreme heat.

Those are just a few examples for now, when I'm not essentially brain dead after some sleep I'll edit this lol

[Eroc3k]

VERY INTERESTING. Staying posted cause I'll need to get this down packed soon.

[kirill007]

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?

Red:

There are 3 things that determine a alternator's output, the magnetic field, frequency(RPM) and the amount of windings per phase winding. (also a fourth one, machinefactor)

And obviously the amount of losses determine it's output, mechanical , iron, copper and brush friction losses if there are brushes.

It can be improved but if it's engineered properly you shouldn't worry about it. Usually if you try to improve output it will not last you very long.

Blue:

It is possible, but at the expense of reliability and the output gained will not be worth the risk. You might even lose output because it get's too hot (copper losses), usually heat is the limiting factor or saturation of the magnetic field. (It should saturated slightly stock to give optimal performance)

You can also rebuild it for higher RPM, but that will make it less useable in a daily situation and wear out the bearings ( and brushes) faster.

So the best thing to do with anything you buy is to buy something you know will last you a long time even if it seems to cost a lot more.(by that I mean purchase price vs usefull lifetime of the product)