Here's some info from the sales slip...

Alternator pulley:
Cast Iron, Number of Grooves 1, Bore Dia. 5/8
In., Outside Dia. 2.55 In

7.25 inch pulley
Cast Iron, Number of Grooves 1, Bore Dia. 5/8
In., Outside Dia. 7.25 In

10. inch pulley
Die Cast Zamak 3, Number of Grooves 1, Bore
Dia. 5/8 In., Outside Dia. 10.00 In

 

Been nearly an hour since your post. Did you figure out the ratio(s)? I've given you the numbers a couple times; you should be able to figure all these things out on your own now.

 

Short Blurb:

The rotor is connected via brushes. Some alternators ground one side, others connect one end to positive and still others make both ends available.

The diodes are in the alternator.

The regulator can be external, it can be in the ECU or it can be internal.

Internal has 3 pins and ground.
1. battery (output)
2. Acc
3. Lamp
4. Ground
I hope that's right.

Acc is ued so that there is no parasitic drain when the car is off. The lamp is driven when discharging.

The output of the alternator is 3 phase. The rotor creates the magnetic field. In stand-alone alternators, there may be an extra winding where "residual" magnetism provides power to get the alternator going.
In generator talk, there is the notion of flashing. This provides residual magnetism. It is a process externally done to the alternator.

The pulley is a PITA to get off.

I've seen two concentric brushes and I've seen one with the brushes at right angles.

Because of which side of the rotor is grounded in operation, regulators have a different design.

 

To get the ratio you'll need to work backwards. Start with the desired RPM of the alternator. Lets assume you want 5000 RPM. (and keep in mind I am making many assumptions based purely on the numbers)(this doesn't mean that 5000 RPM is what you want - for that you're best off talking with someone who KNOWS the ideal speed - I don't). OK, so assume you want 5K RPM. How many RPM does your motor expect to spin at on 12 volts DC? (Actual speed may depend on whether you're powering it with a car battery - potentially 13.5 volts). Lets assume your motor spins at 3900 RPM. Your ratio would be 3900 to 5000. (OR 39 to 50). Off hand I would guess that your pulley diameter on the alternator is around 2 1/2 inches (2.5" assumed). Divide 3900 (assumed motor RPM) by 5000 (assumed target alternator RPM) and you get 0.78. (3900 ÷ 5000 = 0.78) Take the reciprocal of that (1 ÷ 0.78 = 1.282) and multiply that by the alternator pulley diameter (2.5" x 1.282) for a motor pulley diameter of 3.205 inches. A ratio of 1 to 1.282. For every single rotation of the motor the alternator will rotate 1.282 times.

Lets check the math: 3900 (motor RPM) x 1.282 = 4999.8 (alt. RPM).

Keep in mind that the larger the motor pulley the faster the alternator will spin. HOWEVER the larger the motor pulley the more torque you place against the motor. In other words the motor will slow down with the more load you place on the alternator. The total power you'll be able to generate with the motor/alternator combination will largely depend on how much power the motor can produce. Take into account other factors such as friction and heat loss and your power output will drop.

If the motor is capable of (as you said, 60 or 70 amps)(12 x 65 =) 780 watts then (in a perfect scenario) the alternator will be able to produce no more than 780 watts. Since we know there's going to be loses I'll guess (I said "Guess") that you're total wattage output capabilities will be around 550 watts. (780 x 0.7071) or little more than 45 amps.

You said you're planning on running this motor with a small lawnmower battery. IF the battery itself is not capable of producing 45 amps (and you said your motor draws 60 to 70 amps) then you're building a ship out of screen door materials. It's not going to float. EVERYTHING needs to be taken into account in order for this to work. Which leads me to wonder why you want to take 12 volts to generate 12 volts. I'm sure you have your reasons though. Hopefully you can find the answers you seek.

May the force be with you.

1. Lets use 5000 rpm /s
2. The lawnmower battery isn't big enough ( I have to recharge it to get the motor to even run )... I will buy a auto battery whenst the time comes
3. Let me find the speed of the motor...

will be back

 

The alternator pulley is 2.55 ( your assumption was correct )

The motor is a Leeson 3/4 hp , 58 amps , and 1800 rpm /s

ratio is 1800 to 5000 = 18 to 50
1800 divided by 5000 = .36
reciprocal of that is 2.777777

Number of Grooves 1, Bore Dia. 5/8
In., Outside Dia. 2.55

12 voltage
58 amps
.2068966 resistance ( according to app )
696 Power

I will check back later
thanx for your help in this
R
ps I don't think this is an automotive project per se
I think its a motor project ( but at this point who cares )

 

Is the above correct? ^...

But simply spinning an alternator isn't going to produce any power. It first needs to be excited by a voltage from a battery. Even a low voltage can excite enough energy to bring the alternator up to full potential.

Could you expound on this^...


other questions that come to mind this morning...
1. In a automobile situation the alternator is already in a closed circuit? A. My alternator is sitting on a bench and has to be excited ... every time it is disconnected? or does the residual magnetism/electricity stay? B. Do I need a two batteries or is one ( bigger one of course ) enough...

2. Also in an auto. situation air is forced into the engine area naturally ( because its moving forward ) will I have to have a fan blowing on it to keep it cool or does the spinning motion keep it kool inside the alternator body?

3. Assumption is a great tool when building something...but wouldn't a voltmeter or ammeter in the direct path of the alternator ( produced energy ) load answer a lot of questions...?

4. Lastly...the lowly alternator sitting in an auto. goes thru a lot in its energy producing life time ( ppl turning the ignition key whenst the engine is already running... ppl jumping the batteries of their cars with no clue of the damage they cause... etc. fire trucks, ambulances, heavy industrial movers all have alternators... IMHO alternators are quite kewl...

R

 

Expounding:

When spinning, the alternator is just a mass of steel, copper and other materials whirling around doing nothing more than moving air. For ANY generator to work there must be a magnetic force. I once met a railroad engineer - maintenance man. He was called out to a train engine that was running but was producing no electrical power. Takes electricity to make trains move. The problem was that the batteries were dead (the batteries that excite the armature (rotor) (spinning mass) had no power, they were stone cold dead. The diesel engine has an "Air Driven Starter" (ADS) and the diesel does not need electrical power to run. So they started it but with no electricity it wasn't going anywhere. So (I think his name was) Bob took his flash light batteries and made a temporary contact with the armature windings - long enough to produce an electrical current capable of establishing the slightest magnetic field. The generator came to life and the train was on the move.

There are two types of alternators I'm aware of (there are probably more). One has a permanent magnet in it. Spinning that magnetic field within the stator (stationary windings) is what generates the electrical power. Any time the magnetic field changes polarity it causes electrons to move in the new direction. The train generator and your car alternator are similar in that they need a magnetic field in order to generate electricity. So when you need to "Excite" your alternator it simply means that it needs a little bit of electricity to generate the magnetic field. Once that magnetic field is there the alternator can produce enough electricity to make its own magnetic field.

I said there were two types of alternators - I'm just learning that there is another that has some sort of residual magnetic field so that it is "Self Exciting". No need for an external power source to get it going. I've just heard about them and know nothing more than what I've explained; and at that it may be incorrect.

Anyway, to answer the rest of your questions:
1A) The alternator body is typically negative (or ground). And in light of what I'm learning and what I know of - I'm going to say that your alternator PROBABLY will need to have the "ACC" powered in order for the alternator to generate power.
1B) Batteries: Well, if you take 10 batteries rated at 12 volts, 20 amps and hook them in series then you get 120 volts 20 amps (DC). If you take the same batteries and hook them in parallel you get 12 volts, 200 amps. I'm not sure of your understanding of that part of it so I can't answer your question because I'm unsure of how you're thinking. I will tell you this: As far as the alternator is concerned it only needs 12 volts and a small amount of current. You don't need a big battery to get the generator up and running. As for the MOTOR driving it - if it's 12 volts then you certainly don't want two batteries in series as that would give you 24 volts and you'd probably destroy your motor. Parallel would be the way to hook them up. What's the benefit of having two batteries? LONGER POWER. "Longer?" Yes. Batteries are not only rated in voltage they're also rated in Amp Hours (aH). Your 12 v 20 aH battery can give you 20 amps for one hour or 1 amp for 20 hours (or some combination there-in). Two batteries would give you 1 amp for 40 hours OR 40 amps for one hour. Exactly what you need - you have to decide (engineer) what works best for your application.

2) Air cooling: Older alternators had fins (fan) on them. I haven't seen many with fins in a while but then again I've been dealing with foreign cars for a while. If your alternator has fins either on the outside or possibly on the inside then it should be self cooling. If not - consider a fan. Especially if you're going to be generating high currents.

3) Assumptions: When you KNOW what you want and how to get there then there's no need to start with any assumptions. But when working toward a goal with an unknown path, assuming certain parameters can help you get close. Then from there - collected data and test results can lead you to change the parameters until you achieve the final goal.

4) Yes, they are put through a lot. Keep in mind; an alternator designed to put out 60 amps CAN put out more. But at a huge cost. For starters you blow out diodes, and can damage internal regulator circuits. But if you didn't blow out the diodes - the excessive load can overheat the coils that generate the power. THAT TOO can kill an alternator.

I have a question for you: It would be interesting to know how old you are and how much study you've done in the field of electronics.

'av'a g'day mate.

 

Lets use 5000 rpm /s

If it is a lawn equipment engine/motor, your RPM number is too high. Any 4cycle lawn mower or other equipment engine is usually governed to 3600 RPM at full throttle. Unless you have removed the governor link it should be right around 3600RPM give or take a small amount.

 

If it is a lawn equipment engine/motor,

No, he's using a DC Electric motor. Which is why several posts ago I asked him if he was trying to build an Over-Unity machine. He says he's not. So I don't know what he's making - or experimenting with - or learning from a home lab experiment. His electric motor turns 1800 RPM, and a pulley ratio of 2.84 to 1. At that ratio his alternator should see little more than 5000 RPM. (7.25 to 2.55 pulley ratio) (2.84 to 1).

 

His electric motor turns 1800 RPM, and a pulley ratio of 2.84 to 1. At that ratio his alternator should see little more than 5000 RPM. (7.25 to 2.55 pulley ratio) (2.84 to 1).

I have a DC motor controller ( 50A Digital DC PWM motor speed controller ) that I bought awhile back just for kicks ( just in case ... of what I haven't the foggiest idea ... yet)

In jan of next year i'll be 60...

I understand in the states that electricity is generated in 3 phases and is transformed into the higher voltages to be distributed amongst sub stations and re transformed into smaller voltages and higher currents and is further distributed down our streets into single phase 240 = two 120's and a neutral along with a common ground ( ground into the earth ). 240 for the oven's, stovetops , laundry driers and Air Conditioners and 120 for all else...

In electronics I understand that ben franklin was wrong ... that emf comes from the neg side of the battery ( but try telling that to ppl that just put gas in their cars and turn the ignition and ac/heaters on )

Lastly... my interest/s are only focused on alternators...

R

 

Nice to make your acquaintance Randy. I'll be 59 in January. (sucks getting old).

 

Nice to meet you Tony...where r u from?

(sucks getting old).

Nah...not really. Whenst u have a handle of your limitations and a repeated copy of your goals...piece of cake!

Moving forward:
So... electricity ( albeit small ( assumption )) introduced into the system ( alt. ) makes it produce energy... ( a given )

1. how does the regulator know ( assumption ) how much the alternator needs ( load )
whenst driving the mustang around ( observation a. ) I notice in park that the engine slows down whenst I turn the head lights on and a heavy slow down ( observation b. ) whenst the air cond. turns on.... but I don't notice ( observation c. ) anything difference in when driving along and turn " any " instrumentation on..............

2. How do I replicate all of number 1 on a bench with just a dc motor and a alternator?

R

 

and re transformed into smaller voltages and higher currents and is further distributed down our streets into single phase 240 = two 120's and a neutral along with a common ground ( ground into the earth ). 240 for the oven's, stovetops , laundry driers and Air Conditioners and 120 for all else...
R

The single phase line is likely between 3.3. and 35 kV which eeds the primary of a residential transformer. The secondary is a center-tapped 240 volt transformer. The center tap is neutral. Earth is provided at one point near the power input, typically from a ground rod, to the residence. Neutral and earth are connected together at the main panel.

Further distribution (sub-panels) in the residence keep ground and neutral separated in the sub-panel.

 

The single phase line is likely between 3.3. and 35 kV which eeds the primary of a residential transformer. The secondary is a center-tapped 240 volt transformer. The center tap is neutral. Earth is provided at one point near the power input, typically from a ground rod, to the residence. Neutral and earth are connected together at the main panel.

Further distribution (sub-panels) in the residence keep ground and neutral separated in the sub-panel.

side bar:
It looks to me that the utility company is using smaller type ( newer ) transformers ( much smaller too ) in our " residential " area ...the older type transformer ( on the pole at my connection ) runs three or four houses of the 240 ( secondary ) and its an older type ( big ) also I noticed they are putting switchs on each transformer where in the past if something blew, the whole street stopped dead...

what brings you to this thread post...

R

 

The car engine has a natural power curve where it produces the most power at a certain RPM. Above and below that the engine power drops off. At idle it's "BARELY" running. ANY additional load will bog the engine down. Small loads like blinkers or the radio won't put much of a load on the alternator so you wouldn't very likely notice that. But when you switch on the AC the engine actually has to increase power to keep the same RPM. Notice it or not - the car makes adjustments to the idle. Most cars do so with the use of an IACV (or Idle Air Control Valve). It's a mini version of the throttle body. Along with the increased air intake more fuel is added to the air stream to keep the engine running efficiently.

Here's an experiment you can try: Grab hold of a cheap DC motor - something out of an old tape deck or CD player. Spin the motor and notice how it slows to a stop. Then short the leads together and give it a spin. You'll notice that the motor stops almost immediately. Why? Because by virtue of the permanent magnets, it's actually generating a small current. Now: Grab an LED and make the connection from motor terminal to motor terminal. Spin the motor. Did the LED glow? If not, spin it the other way. I bet it did that time. And unlike before it neither spun for a short time, nor did it stop almost immediately. The reason for the difference in how fast it slows down is load. Granted, a dead short is about as great a load as you can put on it. An LED will put less load and open leads will put no load on it. Same is true of an alternator in a car. It's producing electricity same as the small motor. Only on a larger scale. If you were to dead short the alternator (DON'T TRY THAT) the alternator should stall almost immediately. Now, I said "Don't try that" because if you do - you'll be replacing the guts (Diodes and regulators).

You ask how the alternator knows how much to put out. It's done by simply watching the output voltage. When you place a heavy load on it the voltage (or current - I'm not sure) will drop. That drop triggers the regulator to apply more power to the rotor. More power there means more magnetic energy to be transferred to the stator coils. Hence, output is regulated by controlling the input to the rotor.

By the way, i'm in Utah. From California, lived in Connecticut, Texas (Houston), Wisconsin and here. Took electronics back in high school - a very long time ago. Raised a family and got away from the electronics practice. Now I find so much has changed I feel like a sophomore again. But I like messing with the stuff. And learning new things. Oh, and helping others when I know (or believe I know) something. But lets keep this forum for the purpose of discussing publicly questions and answers regarding the post. If you like you are free to send me an e-mail. Just click on my profile and you'll find the links somewhere in there. I think it's "Start a conversation".

 

I will email ( start a conversation ) as soon as get this particular business out of the way...

1. I'll try the experiment ( at a later time - whenst my electronics come out of storage ) but for now i'll take your word for it...

It's done by simply watching the output voltage

that's kinda of an ambiguous ( un clear ) statement ...
take your time ... use as much space ( as much as u like ) and explain in simple ( you can never hurt my feelings ) terms what you mean by that...
Its as if there's a brain sitting inside a voltage regulator ( clever name )....

R
ps that's why I was amazed this thread went to " automotive "

 

It's like an air pressure regulator. If the output pressure drops the regulator compensates by adding more pressure. In an air pressure regulator it's done with a spring, a diaphragm and a tensioner knob. When back pressure (on the regulated side) goes up it pushes against the diaphragm causing the inlet (higher pressure) air to be blocked. As you squeeze the trigger of an air gun the drop in pressure allows the diaphragm to relax and the valve opens, thus allowing more air into the hose. The spring helps close the valve. When pressure drops the higher pressure pushes against the diaphragm and spring. The knob sets the spring tension so you can regulate how much pressure is present on the regulated side.

The electronic regulator circuit is similar but without springs, knobs or diaphragms. If the line voltage (as picked up by the 'Sense' line) drops then more power is sent to the rotor. If it goes up - the rotor gets cut back so as to not over-produce electrical power.

If I were to build a regulator from scratch - without knowing anything about how its done now - I'd probably start with some sort of voltage dependent oscillator, kind of like a PWM. The lower the voltage the longer the PWM stays high during its duty cycle, thus, producing a higher voltage.

Now, I mentioned that I don't know for sure how alternators regulate power, whether it's done by sensing voltage or by current. One thing is certain, however it is done (I'll call it power) when the power drops then the alternator responds by generating more power. When the demand drops (or stops) then it produces less (or no) power.

Back in the 70's I heard of someone who built a regulator with some sort of built in Hysteresis. The battery in the car would be charged to some voltage (probably 13.6 or 13.8) then the alternator would completely shut down and not kick back in until the battery voltage dropped down to something lower (possibly 12.6 or 12.8). During the "OFF" time there was no parasitic drag on the engine and this was supposed to give you better gas mileage. So I imagined building the same thing with a few modifications. When you step on the brake pedal it would trigger a regeneration, using the extra drag of the alternator to help slow the car down. Also triggering a regeneration whenever you lifted off the gas completely (slowing down or idling). Switching the air conditioner on would send the alternator into regular mode - charging as normal.

I never built anything like that - probably saved money by not wasting my time. I doubt there would have been much gas mileage improvement, but I never tested out that theory. Perhaps one day I'll actually build such a thing and try it out on one of my drives to Idaho (to buy lottery tickets (yeah, like that saves money)).

Anyway, the thing about alternators and internal regulators is that I don't have to worry about how much it's generating. Back in the 80's I drove a Ford Granada with an external relay type regulator. Sometimes it would stick. In the morning drive to work sometimes I'd notice that my headlights were rather bright. Bright enough to notice by eye. So I'd roll down the window, reach out and slap the fender. The lights would dim (to normal) and I'd continue on. That went on for only a few mornings before I replaced the sticking mechanical regulator. Interesting devices. I never did figure out how they worked.

 

Missed that part, saw he was using a lawn more battery and thought he was also using that motor.

Back in the 70's I heard of someone who built a regulator with some sort of built in Hysteresis. The battery in the car would be charged to some voltage (probably 13.6 or 13.8) then the alternator would completely shut down and not kick back in until the battery voltage dropped down to something lower (possibly 12.6 or 12.8).

This is not how a car alternator works. After the battery is recharged to replace the power used to start the engine, all of the electrical systems and needs are met just by the alternator. The battery in effect becomes a "bypass capacitor" to the system.

 

This is not how a car alternator works.

I know that. I was speaking of an article someone did on alternators and extending fuel mileage. Back in the 70's they were trying all kinds of things from water injection to magnets on the fuel line. Removing the fan belt that drove the AC compressor, specially designed carburetors that ONLY sent fuel vapors into the intake (which is what fuel does in the intake anyway). There were LOTS of tricks to get better gas mileage. As soon as gasoline hit a dollar a gallon, something we all thought would never happen, everybody wanted to extend their gas mileage. I even tried water injection. I swore it gave me better gas mileage, though I could never prove it.

The idea behind the hysteresis alternator was to run the car off the battery and to charge it only when it dropped so low. During braking, slowing down and idling, the alternator could charge. But during acceleration the alternator shut down leaving the extra power to move the car. LOTS of things were tried. They are still trying them. HHO for instance. Even I tried that. Didn't find a way that worked but I did find a nice way to fill a balloon with HHO gas and detonate it. WHAT A BANG THAT WAS. Shattered a window.

Alternators work the way they work. Someone merely tried to find a way to make one work with gas mileage in mind. That's all I was saying.

 

you guys scared me... I thought there was going to be a argumentative debate ( as I was going along my busy day reading with my iPhone ( to keep up on things here ))...
so let's list the things we know so far about my particular project...
1. the alternator has to have an initial source of voltage ( to produce emf )
2. the alternator has be spun a X amount of spin to function as a generator ( alternator ) of additional emf
3. the load determines the amount of emf to be produced by way of the internal regulator
4. The sensing wire has to be connected so the internal regulator functions correctly
please correct these if need be, add to the list if need be and or subtract what needs to be...

R