Dynamo vs. Alternator

RJohnson · Feb 2, 2001

After looking at the B2710 this weekend at the Fort Worth Stock Show, I was told that all of the B series tractor come equipped with a dynamo (generator) and that Kubota offers an alternator conversion kit. Well my question, Is the conversion to an alternator a better choice than staying with the dynamo? I like the idea of adding additional work lights to the tractors lighting system but am wondering which would be a better choice. Is one harder on battery life than the other? If I decided to add a 12 speaker system /w3tcompact/icons/smile.gif to the tractor would one have an advantage over the other?
Since I don't have a tractor yet, I am seeing what options I should select or not select for that matter. This was one of them dynamo or alternator? Which is better? What are the advantages and disadvantages of each?
Thanks

Randy

Keoke · Feb 2, 2001

The major advantage of an alternator over a dc generator is that it is a three phase unit as compared to a gen. a single phase unit. In simple terms, alternator will give a much higher charge rate at slow speeds (idle) since on one rotation of the pulley will cut through 3 magnetic flux fields instead of just one. Current output of like rated units at high speed will be the same with both types. Brush life with dc generators will be shorter since all output current must go through the brushes. Only the field current (2/4 amps) will go through the alt brushes. The voltage regulator on a dc gen is far more complicated then it is on a alt. It has a cutout relay and a current limiter in addition to the single voltage limiter that you will find on both units. A field relay may be also included in a alt reg. if you have chg lamp on dash.
Low charge rate at idle on dc gen's are sometimes offset by using a smaller pulley on unit. This is ok as long as drive belt wrap area is adequate enough to prevent slipping. Too stiff a belt makes it tough on the drive bearings of the water pump and other accessories. All in all the alt is the better unit but a gen will do the job for you as well. Hope this helps.

george

bpence · Feb 2, 2001

The newer B-series Kubotas come with alternators. I believe the last one to use the dynamo was the B7100 (out of production 95/96) or maybe the B7300 (out of production 99/00). The 2710 you were looking at would have an alternator.

Bob Pence

Bird · Feb 2, 2001

Bob, my '99 B2710 manual says it's a "AC dynamo and a regulator."

And George, I'm not much of an electrician, but my manual says, "This dynamo produces higher voltage in slow speed rotation, and charges electric current to the battery during engine idling."

Bird

TWINKLE_TOES · Feb 2, 2001

Bird,

I think the term "Dynamo" is an old term for generator, be it an ac or dc. Since the popularity of the alternator in cars, tractors etc. The dc generator has become just generator and the ac generator with output integrated rectifiers for a dc output is called alternator. My tractor is three phase, ac generator with full wave rectified outputs.(alternator)

The primary advantage of the alternator is the construction of the rotor. An alternator of the same capacity is significantly smaller and cheaper to build than the equivalent dc generator.

Bird · Feb 2, 2001

Twinkle Toes, I was a teenager working in my dad's auto parts store when the alternators were first introduced. I'll never forget a meeting that was held to teach mechanics about the difference between the generators and alternators. The guy said, "I know a lot of you are used to shorting across the terminals on a generator to see if you get a spark to let you know whether it's working or not. Well, you can do the same thing to an alternator and if you get a spark you'll know it was working; until you did that.

I've got a pretty good digital clamp meter and with the help of the manual I can usually fix most problems, but can't claim to really understand all that electricity very well at all.

Bird

TWINKLE_TOES · Feb 2, 2001

Bird,

I worked in a gas station when I was in high school. It had two bays and we did minor repairs. I remember one of the first generators I replaced, put out a negative voltage, thought I had it in backwards but couldn't figure out how to turn it around. Turns out, the polarity of the output is based on the residual magnetisum in the core, had to run it as motor first to get it turned around. Those were my informative years./w3tcompact/icons/blush.gif

The clamp meter is a great little tool, the best of all worlds. What MFG and model do you use?

ddl · Feb 3, 2001

Technology is interesting is it. As new technology comes along, different names are given, but the old names for older technology seems to be applied to the new tech. One has to make sure you know what the person taslking id really talking about. As I teach college students, that is the hardest thing to accomplish, is that they realize a device may have two or three terms used, then you get into local terms for a device. The term dynamo comes from the word dynamatic or something really new or neat. How it has been used over the years has been a trip!!

Dan L

Bird · Feb 3, 2001

Al, I'd consider my clamp meter to be sort of an off-brand. About 10 years ago, while full time RVing, I ran into a fellow who traveled around the country teaching refrigeration/air-conditioning repair to RV technicians, and he also sold these Extech Instruments AC/DC Clamp Meters. It has Peak Hold, Data Hold, 200 & 400 amp ranges, 200 & 1000 DC volt ranges, 200 & 750 AC volt ranges, ohm meter, and temperature (-40F to +1400F) probe. It's been a good one so far, but I guess if I ever have to replace it, I'd have to buy a Fluke 'cause that's what my brother sells now./w3tcompact/icons/laugh.gif

Bird

TWINKLE_TOES · Feb 3, 2001

Bird,

clamp meter to be sort of an off-brand

Maybe but still a excellent choice. This one is my favorite, after looking long and hard (including the Fluke 33 and 36)
http://www.extech.com/WhatsNew/PDF_datasheet/Datasheets_English/380941_942_947.data.pdf The 30Amp on is the one I like. Most of the ones I have seen lack low current (less than 10 amp) accuracy. Yours looks like it does a pretty good job. One way around this sometimes. Loop the wire thru the jaws a few times and divide the reading by the number of loops.
I met John Fluke in 1968 quite a character. I recall an interview by "Electronic Design Magazine" with John and other CEO's of leading MFG's. They poised a series of questions around how they handled problem employees, most responded with more training, motivation, counseling.... etc., but not John, his universal answer "fire em".

GlueGuy · Feb 3, 2001

Randy,

Alternators, dynamos, and generators all perform the same function. I think the evolution started with generators, which are single phase, with a magnet in the rotor.

Dynamos came along next. They operate similar to an alternator, with (usually) three phases, and the magnet is replaced with a wound coil that is charged from the battery to create the rotating magnet. Principle difference is the multi-phase output from the dynamo is rectified externally, and often in the voltage regulator.

The main difference with an alternator is that the rectifiers were put _inside_ the alternator. Made a smaller package, took all the RF generated by the dynamo and kept it inside the unit. This is important if you have radios and/or electronics that can be affected by the RF.

The newest alternators have gone the next step and integrated the voltage regulator inside the alternator too. In fact, the newest voltage regulators have gone electronic as well. Old voltage regulators were simple on/off switches. They could generate prodigious amounts of noise as they switched on and off. The first electronic regulators were simple electronic switches as well. Still generated a lot of noise. Newest regulators are linear. Modulate the output according to demand, and are very quiet (electronically speaking).

I guess this is all progress. It also means the new alternator/rectifier/voltage regulator is going to cost more than a simple dynamo.

GlueGuy

RJohnson · Feb 3, 2001

Thanks GlueGuy,
That was what I was wanting to know. The sales guy looked the alternator up in the Kubota part manual and it was an add on option for both the B2710 and B2910. I just was not sure if it was worth the $130 list price they had.
After reading about the limitations of the Kubota electrical system, especially the lights, I was not sure to opt out for an alternator.

Randy

Bird · Feb 3, 2001

That's interesting, Al. I'd never looked for them on the Internet. I didn't know much about the meters when I bought mine, but did know I wanted a clamp on amp meter, and I liked the temperature probe (and I liked the guy who was selling them). I would guess mine is obsolete by now; don't see it on their web site, but the 38093 series "looks" more like mine.

You aroused my curiosity, so I had to go look at mine closer and it's a 38091 series, so I guess that accounts for it looking a lot like the 38093, but I don't find 38091 on their web site anymore.

BirdEdited by Bird on 02/03/01 01:15 PM (server time).

bpence · Feb 5, 2001

OOOOOPPPS! Maybe I overstated. Let me clarify. All of the B2410s and B2710s I've looked at over the past year or so had an alternator. I was at the dealer Saturday picking up some filters and asked about the electrical systems on these. The dealer said they only order the B2410-2910 with the alternator option. Many folks adding extra "stuff", so they just upgrade all of them.

Bob Pence

Bird · Feb 5, 2001

And I didn't even know it was an available option, Bob.

Bird

lyon · May 1, 2011

Hi all,
Christ has risen. Hallelujah!

I have a Kubota B1600DT (16 HP-pto output power, 20 HP-engine output
drive: 4WD, 3 cylinder, engine model: D950, in fact 927 cc, the latest year o manufacture 1982). The ball bearing ,-see attachment- inside the alternator ("dynamo"-in part manual book) body is broken and destroyed the permanent magnet. I've replaced the bearing, but I don't have a solution for the magnet. In fact this part is called "FLYWHEEL DYNAMO" -the rotor in fact- and has on interior side the permanent magnet (see pictures attached). Has anybody an idea how to replace this magnet inside the rotor ?. From my knowlwdge this electric generator give out 12V, and 18 Amp.
Thanks !

JimP · May 1, 2011

My 2410 had a dynamo. I never felt like I was underpowered even when plowing with factory lights and electric sander. Try the dynamo first. If you find that you need more power you can always add the alternator later. There are some older threads on this conversion in the Kubota B models.

lyon · May 1, 2011

Thank You Jim. The dynamo don't charge the battery. It is dead. As you can see in the pictures attached the magnet is destroyed. Please give me that older threads/links, or some an alternative solution... :thumbsup: