Tractor starters and magnetic fields

There seems to be a misunderstanding on this site as to where the magnetic field comes from. We all have been falsely tought that the field comes from the current. Take a simple 6 volt starter system that turns over but slow. Take out the 6v battery & replace it with a 12 volt that fits in the same box. The starter spins it over much faster, but the amps are less. The cells in the 12 v are only half as big as the 6 volt battery, thus less amps. Another example, Take a 12 volt system using 2 6 v in series. Engine turns over just fine. Then take the 2 6 v & hook them up in paralell to double the amps & it will be a struggle to turn over. Hook another 6v boost to add more amps & it still wont turn very good.Don"t hold it long or it will burn off the brush wires. Amps produce heat. Heat is a waste, it doesn"t make a magnetic field. Then hook the same 3 batteries together in series & it will spin over like crazy. If you check the wattage (volts x amps) in paralell it will be high but not much happening. In series, the faster spinning armature produces a greater back EMF that further reduces the amps. So the wattage is less but it is getting more done. How can that be? You don"t get something from nothing. The magnetic field doesn"t come from the current but from the atoms of the wires excited by the voltage. E=MC squared.

Troll

If you're smokin' stuff that good, you should share it or at least tell the rest of us where to get it.

Have you ever ran different kind of electric motors in an instrumented lab or are relying on jn seat of the pants dyno results?

(quoted from post at 12:54:52 01/11/12) If you're smokin' stuff that good, you should share it or at least tell the rest of us where to get it.

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in't that the truth!! ampere-turns. more amps or more turns.....or even more of both.

Teddy, it's been awhile. We've all missed your "interesting" posts. Allow me to comment:

"The starter spins it over much faster, but the amps are less."
No. The starter spins faster because it is producing more torque. And it is producing more torque because there is more current going through it at 12 volts than at six. To elaborate, the starter voltage equals the back EMF plus IxR, where I is the starter current and R is the starter's internal resistance. Since back EMF increases with motor speed, the higher the battery voltage the more EMF the battery can overcome. Hence, with a 12 volt battery, the starter current is greater at any speed than with a six volt battery. More current translates to more torque.

"Then take the 2 6 v & hook them up in paralell to double the amps"
No. The current is not doubled when you connect batteries in parallel. There is some increase in current because the internal resistance of two batteries in parallel is half that of a single battery. But it is not doubled. In order to double the current, you need to double the voltage (more or less).

"So the wattage is less but it is getting more done."
No. Not unless you want to redefine "power" and "work". Which of course you and your pal Crackpot Joe do on a regular basis.

"E=MC squared."
It's always good, when you're trying to make a nonsensical argument, to throw in an irrelevant formula from a theory most people don't understand. Point goes to Teddy!

These starter motors have series wound fields and when you increase the voltage you get a proportional increase in current and thus more power and torque. The resisitive power is IxI/R so the heat generated in the winding goes up by the square of the current and you have to watch and not overheat the windings. Keep cranking time to a minimum.

Teddy, where did you study electrical engineering? Or are you just pulling our legs?

More voltage is more current. Electricity is not easy by any standards. Dave

Been working on a project that I THINK will work, but so far it's just in the engineering phase.......what'a'ye think?

<a href="http://s261.photobucket.com/albums/ii44/thurlow8/?action=view&amp;current=perpetualmotion.jpg" target="_blank"> </a>

Teddy,
Lesson on E and M, Electricity and Magnetism.
You can't have one without having the other.
Magnetic fields are a right angle to the direction the electrons are traveling.

One way to measure magnetic strength is with amp-turns. Double the turns of wire, and you double the magnetic strength. Same with doubling the amps, you double the magnetic strength.

According to Ohm's law, doubling the voltage in a DC circuit, you will also double the amps.

In theory, if you were to use a 6v starter on a 12v battery you will double the amps. According to the laws of physics, power is equal to volts times amps. Twice the voltage and twice the amps, you have 4 times the power.

My dad converted an old case tractor over to 12v and he used the old 6 v starter. We just had to bump the starter and the tractor was running.

When tractors are converted over to 12v, are the starters replaced with 12 v starters, or do some of you do like my dad? I don't ever recall replacing the 6v starter on the case.

Where did you come up with E=MC squared? E stands for energy, M is mass and C is the speed of light. This is high energy physics where you have fission or fusion and a loss of mass, not to make things more confusing

George

You leave me speechless. With your sharp intellect and clear grasp of things - perhaps you need to run for president.

Teddy studied at Duggan's Irish Pub under Professor Guinness.

Correct law is 'Ohm's Law'. P=I X E. Power (watts the starter uses) = I (current or amperage) times E (voltage) By going to 12 volts, which is 'electromotive force', or a potential, is to double the available force to move the starter. If the current flow remains the same, the starter can turn faster and stronger because it has more power to turn it over.

You are forgetting E=MC squared.

I'm sorry it should be MC squared=E

Don,

P = I x E is NOT Ohm's law. It is a formula for calculating power. Ohm's law defines resistance, not power.

When you increase the voltage applied to a dc motor, the current does not remain constant. It increases. Motor torque is directly proportional to current.

Now, when you increase the voltage to a dc motor with NO LOAD, it will turn faster. But that is not because it has "more power". It can go faster because there is more voltage to overcome back EMF, back EMF being proportional to speed. But the power does not increase significantly because it is producing no torque, hence it has almost no current and is consuming almost no power.

Jde. Thats what they are counting on. Making you speechless.I was wondering, " What keeps you from biting through your lip, and screaming"IDIOT"till the neighbors call for the folks with the long sleve jacket with the arms tied in back? Always experts here that make statements with out varification of facts. Keep sane J de. Regards, LOU

Possibly make the magnet pole extend and retract that way you would be able to vary the speed. I'm not sure if extending the magnet would speed you up (to keep pace with the magnet) or it might slow you down because of the weaker magnetic field.

Einstein you ain't---

Holy freakin' crap!!! You needs to run fer president of the IEEE!!!

I dunno. Gotta be smarter than what we have--

I don't know. Who is the president of the Institute of Electrical and Electronic Engineers?

Now that I think about it, you're right. Ohm was E= IR. Gotta give me credit- the Navy trained me 45 years ago and most of it's still around somewhere. I just forgot where I put it-- but it's still the formula you're hunting for.

Martyr complex

In psychology, a person who has a martyr complex, sometimes associated with the term victim complex, desires the feeling of being a martyr for his/her own sake, seeking out suffering or persecution because it feeds a psychological need.
In some cases, this results from the belief that the martyr has been singled out for persecution because of exceptional ability or integrity.
[1] Theologian Paul Johnson considers such beliefs a topic of concern for the mental health of clergy.
[2] Other martyr complexes involve willful suffering in the name of love or duty. This has been observed in women, especially in poor families, as well as in codependent or abusive relationships.
[3][4] It has also been described as a facet of Jewish-American folklore.

5 The desire for martyrdom is sometimes considered a form of masochism.
[6] one of several patterns of "pain/suffering seeking behavior", including asceticism and penance.

AND/OR

a person who seeks sympathy or attention by feigning or exaggerating pain, deprivation, etc.

I believe you really believe the things like this you write. That is good in the sense that you are willing to put your self on the line with your understanding. I also believe there are very serious and experienced (competant) electrical engineers on this board. (I teach University electronics and power theory, my beginning students make series wound electric motors from spools of wire, chunks of copper for commutators, and strap iron.) As voltage goes up, amps go up whether the motor is locked rotor stuck, or spinning free. I have them watch the analog meters on the front of the power supply as they twist the voltage control. (smoke starts on these little gems at about 25 volts and 10 amps.)
Reading and fundamental experiences are essential. Consider real evidence and accepted foundation scientific principles befor stringing together incompatible elements of theory. With respect!! I enjoy your normal input on old iron. Jim

Jim,
There may a difference between you lab and a starter on a tractor. Yes, they are both series wound. Difference, the starter is under load and I question if your students have their motors under load. I've seen a series wound motor go into a self destruct mode when the load was removed. Self destruct mode is when the smoke comes out of the motor.

Do you teach your students the electron flow theory or the smoke theory? Under the smoke theory, when smoke comes out of any electrical device, it usually stops working. Therefore, smoke must be traveling in wires, not electrons

BTW, when you go past a power station, you can see the smoke coming out the chimney. They pump the smoke in the wires and when it comes back, the smoke released up the chimney. That's AC smoke Theory.

George

Notice smoke or feel heat either one provides evidence of low performance. Jim

The motors vary from self starting high speed well made spinners at 3 volts, to those that smoke and heat up and do not turn. These are not kits. And I want them to be a representation of effort. Jim

(quoted from post at 18:00:45 01/11/12) More voltage is more current. Electricity is not easy by any standards. Dave

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So, that is why a 12v system has smaller wires than a 6v system is it? To handle the extra amps? Right?

Come on, All you smart guys know better than that.

Come on smart guys,,,,,,,,,what do you say?

Less current is required to provide the same power
on 12V vs. 6V. Hence the light weight 12V cables and
windings.

Teddy aint wrapped to tight.

Are your motors under load?

Smoke theory or electron flow?

(quoted from post at 20:45:00 01/12/12) Less current is required to provide the same power
on 12V vs. 6V. Hence the light weight 12V cables and
windings.

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Exactly! Was that not one of his points?

Who is "his". ?

1. The magnetic strength of an electro magnet is determined by the Ampere Turns.

2. Increasing the Amperes or increasing the number of Turns will increase the flux density and therefore the magnetic force.

3. Every metal core has a maximum number of magnetic lines that it can support when it reaches this point the core is said to be saturated and increasing the Ampere Turns will not increase the flux density or increase the magnetic force.

4. Every motor has at least two interacting flux fields that cause rotation.

5. The torque developed by the motor is &#632;1 *&#632;2 *K (in a motor with 2 fields)
a. Where &#632;1 is the of one of the fields and &#632;2 is the magnetic flux of the second field and K is the design constants of the motor (the K of the motor are always the same for that given motor and do not change)
b. Increasing the flux density or either or both fields will increase the torque the motor can develop (&#632;1 *&#632;2 *K) if you double the flux density of one field the torque producing capabilities will double if you double the flux density of both fields the torque producing capabilities will increase by a factor of 4 as long as the field pieces are not saturated.

6. The current flowing in a motor coil is determined by the difference between the applied voltage and the Counter Electromotive Force (CEMF) produced by motor speed and the resistance to current flow.
a. In a DC motor this resistance is the DC resistance of the coils.
b. In an AC motor this resistance is the Impedance of the coils and the DC resistance.
c. Increasing the speed of the motor will increase the CEMF.

7. The CEMF is always less than the voltage applied to the Motor.

Let us look at a series DC motor like the tractors starter motor, if you run this motor under no load it will run so fast it will sometimes throw the commutating bars from the armature. As you apply a load to this motor it will slow down as it slows the CEMF of the motor decreases so the current in the motor increases.

Conversely to start cranking the starter must make enough rotations to run the Bendix out, once the flywheel is engaged the starter will pull high amperage and the starter motor will begin to gain speed so the current will be decreasing as CEMF increases, at some point the motor will be producing enough torque to turn the load (in this case it is cranking the tractors engine) and it will have some given amount of current flowing in the motors windings (since the windings are in series the same current flows in both windings) let us say for example the cranking amps are 200 amps on a 6 volts system.

Now if you double the voltage to the starter to get enough CEMF to control the current to 200 amps the motor will have to run twice as fast just to maintain the same Ampere Turns. With the same amount of Ampere Turns the starter will produce the same torque as the starter did on a 6 volts system.

Simply stated if you double the applied voltage to a series motor it will develop the same torque at twice the speed, to develop the same amount of torque it will have to maintain the same Amperage because the field strengths have to be the same.

If a starter motor is intended for a 12 volt system if will have twice as many turns of smaller wire when compared to a starter intended to be used on a 6 volt systems if both are designed to produce the same amount of torque.

If you test this theory do not use the figures of 6 and 12 volts but measure the voltage at the Starter terminal and compare by using the actual starter voltage not the nominal battery voltage.

(quoted from post at 16:30:13 01/13/12) Who is "his". ?

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Teddy, the guy you all are running down.

The cables being thinner on 12V systems is simply a cost-savings measure on the part of manufacturers. Copper has always been relatively expensive and battery cables use a LOT of copper. Anywhere you reduce copper usage means more money in the investors' pockets.

The 12V system works "good enough" with the thinner cables. It's not optimal, but it doesn't need to be.

The 12V system works "good enough" with the thinner cables. It's not optimal, but it doesn't need to be.


Yes, because the 12v system draws less amps.