Dynamo vs Alternator

[FrogLick]

Can someone clue me in on the Kubota "dynamo" vs an alternator /forums/images/graemlins/confused.gif. Seems that the dynamo lacks sufficient amp output to be all but useless especially if one wants to add some auxillary work lights.

 

[Av8r3400]

The Dynamo is a small AC generator (alternator), with (I think) something like 15 amps of output.

The OEM unit on my BX was plenty to run the 2 35 watt axillary lights I was using. BTW, these were plenty enough light for night snow-blowing and FEL work.

 

[FrogLick]

I think that you are correct in that the dynamo output is about 15 amps total; it's probably the same one Kubota uses on the B3030. To the best of my knowledge though a dynamo is a generator but not really the same thing as an alternator. It appears that Kubota offers an optional alternator with about 3x the output (45 amps); I think it would also require heavier wiring and the requsite time/expense in the shop to install. I've emailed Kubota for a clarification and will post their response if I get one. Dynamos have not been used on cars and other power equipment for a very long time. Maybe Kubota engineers made a serious design choice error or they just decided to save a few pennies on otherwise well designed tractors /forums/images/graemlins/mad.gif? Then again, I may be mistaken and way off base on this issue. In any case, it's good to know you're not having any problem with 2 35 watt aux lights which would draw about 5.84 amps I believe.

 

[Sully2]

</font><font color="blue" class="small">( I think that you are correct in that the dynamo output is about 15 amps total; it's probably the same one Kubota uses on the B3030. To the best of my knowledge though a dynamo is a generator but not really the same thing as an alternator. It appears that Kubota offers an optional alternator with about 3x the output (45 amps); I think it would also require heavier wiring and the requsite time/expense in the shop to install. I've emailed Kubota for a clarification and will post their response if I get one. Dynamos have not been used on cars and other power equipment for a very long time. Maybe Kubota engineers made a serious design choice error or they just decided to save a few pennies on otherwise well designed tractors /forums/images/graemlins/mad.gif? Then again, I may be mistaken and way off base on this issue. In any case, it's good to know you're not having any problem with 2 35 watt aux lights which would draw about 5.84 amps I believe. )</font>

CORRECTO!!! /forums/images/graemlins/grin.gif. As a generator..the fastr you spin it..the more power it puts out ( Up to its max.) As an alternator..that makes 120V AC..and then rectifiers change it to 12V DC)..its output is more "constant" regardless of RPM.

Along with the alternator kit..comes a new wiring hardness to replace the "default" setup.

IMHO..the default..doesnt have enough power to pull the hat off your head...and a winter project for ME..will be installig the Alternator Kit... ( IF its not TOO difficutlt job to do ??)

 

[Toolguy]

I installed the optional Alternator kit on my B3030. My dealer made a great deal for my by selling it to me for $150. List is like $179 or so. It is not too hard to put on. Took me an hour or so. It really make a difference in output. The stock dynamo put out about 13 amps. The alternator puts out about 43. That is more than enough to run the three 55 watt lights I added.

 

[Mike_Lipke]

If Big Orange made an error, so did John Deere, as they use them also.

 

[AceDeuce]

It seems to me the most likely reason for using a dynamo over an alternator is simply that a dynamo is all that is needed. There is no computer or other sophisticated electronics. Just a fuel pump, a starter motor, lights, solenoids and a few safety interlocks. It's really a very simple electrical system. Now, if you want to wire up your tractor for enough lighting to turn night into day you might need a little more output than the stocker can handle. An alternator is definitely a good choice for that, but the primary reason for an alternator system over a generator is constant voltage.

 

[MadReferee]

AceDuece got it correct. It is just not cost effective on the lower end machines to put an alternator when a much less expensive dynamo (generator) setup will work just as well. Be happy that the upgrade option is available. It's not all that expensive for those that need the extra oomph of an alternator but it's really cost prohibitive when you figure putting them on hundreds of thousands of units being built.

 

[Charliebrn]

I posted a project on this some time back, complete with pictures. It wasn't a bad job at all, took me a couple hours, beers and all. /forums/images/graemlins/grin.gif The docs that come with the alternator kit were awful, so I think you'll find my docs quite a bit better.

 

[techman]

In spite of Kubota's naming conventions, the Kubotas have an alternator, although a small one. I don't believe anybody is using a brushed DC generator anywhere, mainly due to cost alone.

paul

 

[Volfandt]

True, the Kubota Dynao is a low wattage alternator in that it makes AC voltage and uses a standalone rectifier/regulator to convert the voltage to DC and control the dynamo's output.

I don't have much of a demand for more wattage out of my BX23 but if I needed more light's etc., I'd be upgradeing to the alt kit mosh-kosh /forums/images/graemlins/grin.gif
Volfandt

 

[Keoke]

Techman, you are right in that no one makes DC generators anymore. There is no difference between an alternator and a dynamo. The Japanese and Europeans have called alternators dynamos for a long time but here in the US the dynamo name has never took hold.
Small (low amps) alternators on tractors tend to have their rectifier diodes external mounted (often in voltage reg) while large units will mount diode's internally to take advantage of fan cooling.

 

[djg]

I was taught in tech school that what we call an alternator was invented by chrysler when they put air conditioning in cars. The common DC generators of the time had insufficient output at low RPMs, and the battery would discharge if the A/C was used around town. This alternator has a rotating field coil that requires an input of electricity, which is fed through two brushes. There are three coils spaced around the rotating field that produce alternating current. This current goes through a diode matrix to produce DC. The dynamo as used in Kubotas is a permanent magnet rotor rotating inside a coil that produces AC, which is rectified by an external unit. It has only two wires coming out of it, and they can be attached either way, which is to say they have same color code. If you spin a dynamo by hand, you will feel a rythmic resistance as the magnet spins. It feels like a magneto when you spin it. The dynamo does not require any input of electricity, it has no brushes, it is weak at low RPMs. It is not the same as an alternator, as these terms are commonly used today.

 

[techman]

Actually as a device, the alternator is a very old device, predating the auto industry.

Alternator by definition produces an "alternating", or AC output. The technology uses some sort of magnet, usually as the rotor, although the magnet as the fixed coil was used in a number of designs. The rotating magnet is commonly known as a "rotating field" design.

The magnet can be a perrmanent magnet, as mentioned, or an electromagnet. The latter is known as as wound field or rotor design. Wound rotor units have the advantage of being able to vary or regulate the output voltage of the alternator by varying the magnet's strength. This comes at greater complexity and cost. A permanent magnet design is cheaper to make, but the output voltage varies with the RPM of the shaft. Some smaller AC power generators use permanent magnet rotors, since the RPM is basically constant, for 60 Hz output.

The king of the alternator is the brushless alternator. It has an electromagnet field coil that is fixed, which energizes (excites in correct terms) a small alternator coil on the rotor. The output of this small alternator is rectified by diodes on the rotor and feeds DC to the wound rotor of the main alternator which is down the shaft a bit further. The main alternator output comes off of the coils in the stator that are coupled with the main wound rotor. To vary the output voltage, the electromagnet field voltage of the small alternator (known as an exciter) is varied. This varies the resulting DC voltage to the main rotor field, and thus the AC output. Complex and expensive, but no brushes to maintain and the ability to regulate the output voltage.

I do not know who was the first, but the use in cars was to meet higher power demands (perhaps due to the A/C). The alternator design can produce more current as lower RPMs, if it is designed to due such. The other advantages were a smaller size and lower production cost. I suspect that the latter issue was what motivated the automakers.

paul

 

[Keoke]

Dig, you are correct, Chrysler introduced the dynamo in 1960 and called it an alternator. I guess it is because they felt it is an AC generator that changes (alters) that AC current to a DC current.
The difference between the PM (permanent magnet) and a variable magnet (electro magnet field) alt. influences the ability to vary the charge output of the dynamo/alternator.
Both of these units (fixed or variable fld) can be called dynamo's or alternators, use which ever handle you prefer.
If you look European or Japanese manuals printed for home use you will see alternators referred to as dynamo's.
Also, if you look at Bosch service manuals you will see their both their PM and EM alternators frequently referred to as dynamo's.

Current flow on fixed fld (PM rotors) is regulated by the CEMF put out by the battery. When battery is low or load is high flow will be high as battery offers no resistance to flow from alt.. Current flow will taper off as battery voltage climbs and counters alternator voltage.
This type of control is adequate for low load electrical systems but not for high amp units.

 

[midlf]

Alternators with DC output were not practical until the development of high current solid state diodes. The permanent magnet alternator, referred to here as a dynamo, uses an external regulator to interrupt or shunt the fixed output of the alternator. This is a common system on motorcycles, and I suspect ATV's. The "alternator" upgrade referred to here uses a regulator that controls the field current to the alternator to regulate the output, like an automotive alternator.

 

[Bearman1977]

I have a Kubota (Year 2016) B2601, and I just completed installing the Alternator Upgrade Kit (Kubota Part Number 6C040-9530-6, this kit contained everything needed to "Finally" have the electrical power (14.5 amps to 40 amps) for external work lights. It was well worth the investment of $210.00, next day shipped to me, and took me 1.5 hours to install in my own garage. Exceptionally easy to install. One thing I immediately noticed when I started it up, was a noise reduction, and a quicker start up. Strange but true. I would recommend to anyone owning a B series Kubota to invest in the Alternator upgrade, it's worth the additional money! Lastly, Many thanks to the folks over at Messicks Tractor Supply for taking the time and ensuring that I received the right upgrade kit. :drink: