transformer for multiple 12vdc sources?

[Guest]

so i've been thinking on this.. in my applied electrical class we have recently discussed transformers with multiple secondary coils.. what do you guys think ( obviousy, if they make the right one ) of using a transformer in the ac portion of the wiring between the r/r and stator with 2 secondary coils with a second rectifier and use the second coil tap for things like extra lights or whatnot?

[GQROD]

There is a transformer on these bikes? where? ( sounds good by the way and makes sense on the secondary tap. )

[bonanzadave]

use the second coil tap for things like extra lights or whatnot?

Would you need a second battery ?

[seuadr]

no there isn't.. but i can't imagine why there couldn't be.. as long as you have ac current being produced, it could power the transformer.

[seuadr]

Would you need a second battery ?

i'm not sure, to be honest with you. i would think that if the lights were lower current and you didn't mind the fact they aren't on when the bike isn't running..

i am thinking of using aux lights for lighting in the front, but i know the gs's don't produce an overabundance of current to be used for lights.

[mottyl]

If you are trying to get more power from your electrical system it wouldn't work. A xfmr can do many things but it has losses and limitations.

I think all you would be doing is adding one more load onto your electrical system.

But then again I have been out of school for a while.

C

[duaneage]

so i've been thinking on this.. in my applied electrical class we have recently discussed transformers with multiple secondary coils.. what do you guys think ( obviousy, if they make the right one ) of using a transformer in the ac portion of the wiring between the r/r and stator with 2 secondary coils with a second rectifier and use the second coil tap for things like extra lights or whatnot?

Why would you want to do this? Sure there is 80 VAC on three legs but are you planning to run a laptop computer or power the house?

[posplayr]

Sparks and Magic II

If you are trying to get more power from your electrical system it wouldn't work. A xfmr can do many things but it has losses and limitations.

mottyl is right; the transformer is essentially a passive device so it only "transforms" power from one form to another it doesn't create any power. In addition, and as mottyl said if anything it is lossy.

At the risk of over generalizing and over simplifying
Another way to look at it is : if you had a design where one transformer transformed the total power in the system, and then you tried to add another, one of two things would happen:

If the transformers were is parallel, then they would nominally share the currents in the primary current and so the outputs currents would be 1/2; but since there are two the total current would be the same as one.

If you put the transformer in series, then the drop across either would be have 1/2 the drop coming from the stator and so each would be producing 1/2 the power or together the same as a single.

Again, this analysis is essentially the equivalent of the first as no configuration of transformers actually produces any power(i.e. they are passive), it only transforms what is already in the source.

Pos

[seuadr]

Why would you want to do this? Sure there is 80 VAC on three legs but are you planning to run a laptop computer or power the house?

not at all.. i planned on rectifying it back to dc, it's my understanding (and perhaps, i am wrong?) that our generation system doesn't really produce more wattage than the system takes to run? higher wattage spotlights, heated accessories, and the like would draw alot of wattage that (again, mebby i'm wrong) than the system produces.. this seemed like a way to have more avaliable power?

[seuadr]

mottyl is right; the transformer is essentially a passive device so it only "transforms" power from one form to another it doesn't create any power. In addition, and as mottyl said if anything it is lossy.

At the risk of over generalizing and over simplifying
Another way to look at it is : if you had a design where one transformer transformed the total power in the system, and then you tried to add another, one of two things would happen:

If the transformers were is parallel, then they would nominally share the currents in the primary current and so the outputs currents would be 1/2; but since there are two the total current would be the same as one.

If you put the transformer in series, then the drop across either would be have 1/2 the drop coming from the stator and so each would be producing 1/2 the power or together the same as a single.

Again, this analysis is essentially the equivalent of the first as no configuration of transformers actually produces any power(i.e. they are passive), it only transforms what is already in the source.

Pos

i'm talking about a transformer with two secondary coils, they are sometimes used in airconditioning. they can produce , for instance, two different voltages on the secondary sides. my thought was that you could utilize that with what is produced in AC and rectify it back to dc and get reasonable voltage from it.. i guess i was wrong?

it was an idea i had at school today. i don't know offhand how much AC voltage the stator produces and etc to know if it would be a viable option. which is why i posted here so someone could point out why it wouldn't work or whatever.

[posplayr]

Manual Regulation with and external load

not at all.. i planned on rectifying it back to dc, it's my understanding (and perhaps, i am wrong?) that our generation system doesn't really produce more wattage than the system takes to run?

Kinda but not really. The system is closed loop (i.e. there is a regulator) that shunts what is not needed to keep the voltage in the system (nominally at the battery) within range.

The power in the stator is almost completely controlled by the RPM. The unused power is shunted to ground. At idle there is no excess power and you will notice your light dim when the blinker blinks. The only time there is excess is when the RPM's are high. You can add additional load at that time without using any additional transformers.

In a nutshell, anytime the R/R is regulating (likely at Vout>14V), then there is excess power and you could use it instead of having the regulator shunt it. But when the RPM drops and your voltage is back to <13V you better remove the load or you will start to significantly discharge your battery. Essentially that is what the /R part of R/R is doing.

Pos

[seuadr]

Kinda but not really. The system is closed loop (i.e. there is a regulator) that shunts what is not needed to keep the voltage in the system (nominally at the battery) within range.

Pos

well my thought was putting it in line before the regulator, but what you say makes sense, it probably wouldn't produce enough extra to be worth it at idle. ah well, it's just an idea i had while we were doing labs on control circuits

[duaneage]

Without getting academic let's just say power is a function of voltage and current. In this case you have a limited source of both and will get no free lunch. Step up or step down transformers lose power, and the output is dependent on the transformer characteristics. A simple isolation transformer is just that: a 1to1 device designed to protect one side from the other.

The 3 phase system on our bikes was born from aviation, where light weight and high efficiency rule. Bikes share a lot of design elements with aircraft.

The stator has limited current source potential according to the strength of the magnets, the coil winding specifications, engine speed, temperature considerations, and other mundane parameters. On the GS it barely powers the bike and keeps the battery up, providing alternative power sources is a stretch.

[posplayr]

i'm talking about a transformer with two secondary coils, they are sometimes used in airconditioning. they can produce , for instance, two different voltages on the secondary sides. my thought was that you could utilize that with what is produced in AC and rectify it back to dc and get reasonable voltage from it.. i guess i was wrong?

You are not wrong, but what you are missing is that the dual coils are simply a form of power splitting. No matter what form the secondary coils take, there is no more power than what is in the primary coil. In other words the transformers are passive they dont produce power they only transform what goes in.

The following would always be true ignoring losses.

P_in = V_in*I_in = P_out = Vout1*Iout1+Vout2*Iout2= Pout1+Pout2

Pos

[rudy]

Duane and POS are dead right. I'd have said the same, but they beat me to it. If you're looking to power something else, why not just go off the battery, after the rectifier? Obviously you can't add much load such as aux. lights. Convert all your running lights and signals and gauge lights to LED and you may free up a little output power, but there's only so much to go round.

I've actually seen an XS650 with a chrome Chevy 350 alternator hooked up to it. I'm sure his generating capabilities are overkill for whatever lights he wants to put on. He somehow jimmy-rigged a belt drive off the left side of the engine. Looked....... interesting to say the least.

What is it you're going through for in school? I finished my program for electrical engineering technologist a few years ago. Work mostly with freq. drives now and lots of transformers, reactors, filters and cap banks.