Author Topic: Automotive alternator to PM alternator  (Read 21106 times)

0 Members and 1 Guest are viewing this topic.

rustkolector

  • Jr. Member
  • **
  • Posts: 67
Re: Automotive alternator to PM alternator
« Reply #54 on: April 21, 2015, 09:47:33 PM »
Opps!!! I hit the wrong key. Sorry. The maximum output at each RPM was determined to be when the input voltage to the regulator dropped to about 13.3v. Test alternator was driven by a variable speed lathe.

RPM    Volts     Amps    Watts
350      12.0      .99         12
400      12.0     1.88        22.5
450      12.0     2.71        32.5
500      12.0     2.93        35.2 (Voltage regulator maxed out at 3A)

Using a higher amp rated voltage converter the max output at 500 RPM is estimated at 50 watts and 60 watts at 550 RPM. This higher output is not needed for this, or future projects as the alternator/generator above is more than adequate as is. The project 1/8th scale engine is basically complete, and shows good power at 450-500 RPM.  The vintage looking generator frame is in progress. Many, many thanks to all who offered advice on this project and a especial thanks to Flux. THANKS GUYS!
Jeff

Bruce S

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 4431
  • Country: us
  • USA
Re: Automotive alternator to PM alternator
« Reply #55 on: April 28, 2015, 12:53:45 PM »
That is great to see/read.
Would you happen to have pics of the internal windings ?
We like pictures  :D, also gives others a visual of what wave windings are.

Many Thanks for the update too!
A kind word often goes unsaid BUT never goes unheard

rustkolector

  • Jr. Member
  • **
  • Posts: 67
Re: Automotive alternator to PM alternator
« Reply #56 on: February 15, 2017, 08:52:58 PM »
I started this thread a long time ago and must apologize for not posting the finished project. To remind all here,  I wanted to build a small PM alternator based on an auto type alternator stator that I had. My retirement hobby is building working scale model engines based on old slow speed stationary engines of the early 1900ís. I like my model engines to do what the real engines did during their working career. DC power generation was a very common application. So this project was a 1/8th scale model of a 25hp Bates & Edmonds gas engine DC electric plant which required about 36 watts of electrical output at 500-600 RPM. The B&E engine was a very unusual gas engine in that it used the alligator valve link system operated by eccentrics and pull rods to open the overhead valves. The engine runs on propane.

My problem was 18+ volts at low RPM and cogging. In the end, the 12 pole, 36 slot 93mm dia. stator was rewound for higher voltage using the original wave winding, neo magnets were installed on a new steel rotor using the offset method for cogging reduction, and the AC was rectified and regulated for a smooth 12vdc output. The generator was modeled after an early Garwood DC generator. I am very happy with the final project and thought it might be of some interest to those on this helpful forum.

Thanks again for the help.
Jeff

https://www.youtube.com/watch?v=52cj8px3GSA


« Last Edit: February 15, 2017, 08:59:09 PM by rustkolector »

joestue

  • Hero Member
  • *****
  • Posts: 1340
Re: Automotive alternator to PM alternator
« Reply #57 on: February 19, 2017, 11:57:57 PM »
Outstanding work, i am impressed.

how did you make the cams?

hiker

  • Hero Member
  • *****
  • Posts: 1492
  • BIG DOG
Re: Automotive alternator to PM alternator
« Reply #58 on: February 20, 2017, 10:18:04 AM »
Nice.....really loads up the engine when the light is on...35 watts ?
WILD in ALASKA

rustkolector

  • Jr. Member
  • **
  • Posts: 67
Re: Automotive alternator to PM alternator
« Reply #59 on: February 20, 2017, 11:33:55 AM »
Joestue,
Thanks. The engine does not use conventional cams. It uses eccentrics to pull down on a pair of curved and flat levers that depress the overhead valves without putting side thrust on the valve stems. This system was unique to B&E engines. There were many unique engine designs in the earliest days of gas engine development. See photo of the valve levers.

Hiker,
The electrical load in the video was only about 10-12 watts. The engine has no working governor. Scaled down working governors require much higher speeds that prototype to provide adequate working torque. The engine design did not allow such gearing at this scale. I use only a nominal electrical load to demonstrate the engine and generator as a working system.

Jeff


Bruce S

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 4431
  • Country: us
  • USA
Re: Automotive alternator to PM alternator
« Reply #60 on: February 22, 2017, 10:11:55 AM »
What an absolutely beautiful sound! I'd commission one just to listen to it run, if I had any $$$ .

Thanks for the share
A kind word often goes unsaid BUT never goes unheard

george65

  • Full Member
  • ***
  • Posts: 213
  • Country: au
Re: Automotive alternator to PM alternator
« Reply #61 on: February 22, 2017, 05:20:34 PM »
I'd commission one just to listen to it run, if I had any $$$ .


I'd have never thought of Commissioning one. I thought these guys would only do it for themselves but I'm sure some would love the paid opportunity to build another.

I'd rather spend the money on something like that to look at and admire than I would a painting. To my uneducated eye, most painted artwork looks like something I did in kindergarten.

Wonder what an engine like that would be worth to build for somone? $5, 10K?

Bruce S

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 4431
  • Country: us
  • USA
Re: Automotive alternator to PM alternator
« Reply #62 on: February 23, 2017, 07:00:41 AM »
I used to rebuild flathead Ford 4-cyl tractor engines equipped with updraft carbs. It was a labor of fun and love (love = seeing something wore out come back to life and purr ).
Building something like this would be worth whatever , but knowing the hours it took to rebuild a standard ICE , I could only imagine to hours it took to downscale and almost invent everything.


 
A kind word often goes unsaid BUT never goes unheard

george65

  • Full Member
  • ***
  • Posts: 213
  • Country: au
Re: Automotive alternator to PM alternator
« Reply #63 on: February 23, 2017, 07:11:12 PM »

Yeah, I can't even begin to imagine the skills, problems and sheer talent that goes into something like that.
All I know is it's way beyond my abilities to properly even appreciate the brilliance of those that can do it.

rustkolector

  • Jr. Member
  • **
  • Posts: 67
Re: Automotive alternator to PM alternator
« Reply #64 on: March 11, 2017, 08:02:02 PM »
Thanks for the nice comments. I still have one more question on this project relative to rewinding. The alternator stator originally used was from a 40A 12v rated auto alternator. The slots were filled with 2 overlapping coils each with 6 turns of #17 wire. According a chart I found for copper magnet wire current based on AWG standards, #17 wire is rated for only 2.9A. That obviously cannot be correct, or I am missing something. What am I missing?   

What do you use for determining wire size vs current capacity when planning to re-wire a stator?
Jeff

joestue

  • Hero Member
  • *****
  • Posts: 1340
Re: Automotive alternator to PM alternator
« Reply #65 on: March 11, 2017, 10:28:30 PM »
Thanks for the nice comments. I still have one more question on this project relative to rewinding. The alternator stator originally used was from a 40A 12v rated auto alternator. The slots were filled with 2 overlapping coils each with 6 turns of #17 wire. According a chart I found for copper magnet wire current based on AWG standards, #17 wire is rated for only 2.9A. That obviously cannot be correct, or I am missing something. What am I missing?   

What do you use for determining wire size vs current capacity when planning to re-wire a stator?
Jeff

allowable temperature rise under load, that's basically it.

a microwave oven transformer sends typically 13 amps through a 16 gauge aluminum wire, about 100 feet long, you can add it up yourself but lets say 50 square inches of surface area for fan assisted cooling. take the heat lost in the primary and double it, that's probably a safe assumption for the secondary losses. core losses, i have no idea what they actually are under load.

a copper extension cord would probably be rated for at least 6 amps if it was sold as a cheap extension cord. 16 gauge cords are usually rated at 10 amps far as i know. 14 gauge is safe for 15 amps, 12 for 20, 10 awg is .1 inches in diameter and typically rated for 30 amps.

rustkolector

  • Jr. Member
  • **
  • Posts: 67
Re: Automotive alternator to PM alternator - another one
« Reply #66 on: March 22, 2017, 01:05:20 PM »
I am building another one of these generators and would like to make improvements where I can. The first rotor was built on a solid steel core hollowed out a bit to reduce weight. The rotor is in direct contact with the tool steel shaft. I believe it has some torque drag in addition to the cogging. The torque I am referring to feels like a shorted coil, but not as severe. I am wondering if this could be Eddy current drag. It is more noticeable than the cogging at this point. Would a different rotor construction be advisable, or is this drag normal?

Jeff

joestue

  • Hero Member
  • *****
  • Posts: 1340
Re: Automotive alternator to PM alternator
« Reply #67 on: March 22, 2017, 09:03:27 PM »
i would expect to feel significant eddy current drag from an alternator core, i think that's what you were using.

look for a motor typically used to drive the fan in a heat pump. if you're in the usa i could send you this one http://imgur.com/5iztOOb after pulling just the stator stampings out of the sleeve. i have another motor of the same size so i could give you its stack and that would make about  3 inch deep core. i rewound the one in the photo btw just to see if it was reasonable for me to save the motor or melt the copper down. they pulled some shenannigans to fit an 8 pole motor in a 36 slot stamping, you might be able to tell the coil i fitted in there fits in 2 slots on one side and three on the other.

the motor in question is a 5kcp39kf but the ebay listings for that part number don't match what i have exactly. if you drop the last two letters off that part number you'll find a lot of other motors that are very similar.

anyhow the second problem is if your magnets are oversized you will saturate the core and the hysteresis and eddy current drag will be noticable. but if you're using the thick stator laminations from a car alternator, that may be half your problem.

you don't have near enough rpm to worry about what the magnets are made out of, or what's under them btw.


however if the core is saturated you may be able to measure the difference between pressing the stator core into an aluminum housing, or a mild steel one, or open air. some of those older motors had the stator stampings open to the outside air, primarily for cooling, so you may be able to more closely match the original look by bolting the end bells through the motor lamination stack with mere bolts, rather than a tubular shell that covers the entire assembly.

most car alternators did have exposed laminations, but the newer high output ones press fit the stator stack into the aluminum housing so that the aluminum can conduct the heat away from the stator!

if the stator is saturated due to the neodymium magnets you should get the least drag if the stator is not pressed into anything. a compromise would be a non magnetic stainless sleeve. it won't conduct the flux and its high resistance won't generate as much eddy current as most every other material will.
« Last Edit: March 22, 2017, 09:14:24 PM by joestue »

rustkolector

  • Jr. Member
  • **
  • Posts: 67
Re: Automotive alternator to PM alternator
« Reply #68 on: March 23, 2017, 11:51:05 AM »
Joestrue,
This is a scale model project so the small size of the stator is necessary. I am testing performance using the original alternator automotive housing as I did in the first project. The stator is 3.66" OD with a .456" stator lamination thickness. No room left for drilling through the laminations for bolts. The rotor gap was increased to .01" to improve cogging without much loss in voltage. The wave winding coil center width is .625" measured at the slots and the N45 magnets are 1.0" long x .50" wide x .25" thick so about an 80% fill. However, judging from the slight voltage loss when increasing the gap, I would say the stator is still saturated. The stator is a loose slip fit into a .25" thick aluminum generator frame.

Changing to 304 SS for the stator shell would add weight and cost, but if it would significantly reduce the eddy current drag I am feeling with the aluminum frame, it might be worth it. Smaller, or weaker magnets would further reduce voltage at the design speed of 500 RPM. I can afford about a 20% drop in voltage, but actually the voltage is ideal as it is now?

It there anything that can be done with the rotor design or material to lessen this drag?

Jeff

joestue

  • Hero Member
  • *****
  • Posts: 1340
Re: Automotive alternator to PM alternator
« Reply #69 on: March 23, 2017, 11:09:59 PM »
The stator is 3.66" OD with a .456" stator lamination thickness. No room left for drilling through the laminations for bolts. The rotor gap was increased to .01" to improve cogging without much loss in voltage. The wave winding coil center width is .625" measured at the slots and the N45 magnets are 1.0" long x .50" wide x .25" thick so about an 80% fill. However, judging from the slight voltage loss when increasing the gap, I would say the stator is still saturated. The stator is a loose slip fit into a .25" thick aluminum generator frame.

Changing to 304 SS for the stator shell would add weight and cost, but if it would significantly reduce the eddy current drag I am feeling with the aluminum frame, it might be worth it. Smaller, or weaker magnets would further reduce voltage at the design speed of 500 RPM. I can afford about a 20% drop in voltage, but actually the voltage is ideal as it is now?

It there anything that can be done with the rotor design or material to lessen this drag?

Jeff

did you litterally say the stator is .45" thick? if so that's a solid block of iron. usually stators are stamped or laser cut from sheet metal. Even .045" is far too thick.

your observations about the slight voltage reduction from increasing the air gap are correct, its saturated. but its hard for me to estimate what reasonable drag (eddy current or hysteresis or whatever) is without some real numbers.

I have a 1/2 hp motor that is fitted into a 4" diameter brass sleeve. we call these well pump motors, which is what it was.  the stator outside diameter is probably 3.85 inches. the lamination stack is about 5 inches long so the whole motor fits in a 4 inch outside diameter brass cylinder that could be shortened to 8 inches long. the entire motor section of the pump is over a foot long but my point being these small motors are hard to come by.

I also have some 90 watt induction motors that might have less than a 4 inch outer diameter but i'm not sure. they are 4 pole, 1750 rpm, the stator is pressed into an aluminum finned housing that is about 4.5 inch diameter, that is about 6 inches long. i was hoping they would be rated for more than 90 watts when i got them, (that 90 watt rating is for the worm gear drive box they are mated with) but, looking inside the 90 watt rating was appropriate. these dimensions are approximate  btw, i would have to go find them in my stack of stuff and measure them again.


but i have run into a few other people who have had great difficulty sourcing 1/4th hp 3 phase motors. they should be about 4 inch diameter and 6 inches long, but it seems no one makes them.
« Last Edit: March 23, 2017, 11:20:56 PM by joestue »