Kubota Alternator: Using single phase on 3 phase?

[998cc]

Hello to the group.
I am helping a friend with his B7100 engine swap. The alternator on the damaged (non-water pump) engine is three wire, but the alternator on the new engine (water pump) engine is two-wire single phase. The new alternator mounted, but the wiring issue remains. Is there a simple way around this?

Thanks again for the help a few years ago with my B7100. It is still going strong.

Thank you.
Russ

 

[WranglerX]

It's not a phase thing..... A 3 wire alternator usually has a B+ to battery (charge lead), and a lead to ALT light on dash and a 3rd lead to supply +12 volts to alternator to give it initial spike of 12 volts to start charge sequence....

A 2 wire alternator will have a lead from B+ to battery (charge lead) , and most like likely 2nd lead to ALT lamp on dash.... 12 volt to initialize charge sequence is probably through internal circuitry in alternator....

 

[hayden]

It's not a phase thing..... A 3 wire alternator usually has a B+ to battery (charge lead), and a lead to ALT light on dash and a 3rd lead to supply +12 volts to alternator to give it initial spike of 12 volts to start charge sequence....

A 2 wire alternator will have a lead from B+ to battery (charge lead) , and most like likely 2nd lead to ALT lamp on dash.... 12 volt to initialize charge sequence is probably through internal circuitry in alternator....

This ^^^

How are the terminals marked?

 

[ptsg]

While it's technically called an alternator, the OP is referring to one of these and not the conventional alternator as we know it.

These have a standalone rectifier/voltage regulator. Some are 2 wires, others are 3 wires. The B7000 I had, had a 3 wire one, while the Kubota D640 engine I have on my backhoe came with a 2 wire alternator and I had to buy the rectifier for it.

There are rectifiers/voltage regulators available out there for each type of alternator.

There are barely enough to put any charge on the battery and maybe power a light or two. I would suggest to just get one of those 40 or 50A alternators for it. It's a good upgrade.

 

[5030]

I believe Kubota refers to them as a 'Dynamo' and it's basically a permanent magnet DC generator with minimal DC output. Problem is, the minimal DC output is insufficient to power anything but recharge a the starting battery and power a few lights. I would replace it with a one wire GM style alternator of sufficient amperage output to power what you require. One wire alternators are internally regulated so hookup is simple. Of course you will have to fabricate the necessary mounting brackets and match the drive pulley to the existing tractor pulley configuration.

Exactly what I did on my long gone Farmall A. I ditched the OEM generator and replaced it with a one wire GM alternator. Much simpler and less troublesome.

 

[ruffdog]

While it's technically called an alternator, the OP is referring to one of these and not the conventional alternator as we know it.

View attachment 2796564

These have a standalone rectifier/voltage regulator. Some are 2 wires, others are 3 wires. The B7000 I had, had a 3 wire one, while the Kubota D640 engine I have on my backhoe came with a 2 wire alternator and I had to buy the rectifier for it.

There are rectifiers/voltage regulators available out there for each type of alternator.

There are barely enough to put any charge on the battery and maybe power a light or two. I would suggest to just get one of those 40 or 50A alternators for it. It's a good upgrade.

Deere had a simple 20a "alternator" on the diesel X7** garden tractors but offered an upgrade kit to the real 40a. It is not just a simple plug and play swap because of the regulator/rectifier issue. See the detailed instructions for the kit to see how many jumpers are needed.

John Deere 40 AMP Alternator Upgrade Kit - BM20990

 

[rScotty]

I believe Kubota refers to them as a 'Dynamo' and it's basically a permanent magnet DC generator with minimal DC output. Problem is, the minimal DC output is insufficient to power anything but recharge a the starting battery and power a few lights. I would replace it with a one wire GM style alternator of sufficient amperage output to power what you require. One wire alternators are internally regulated so hookup is simple. Of course you will have to fabricate the necessary mounting brackets and match the drive pulley to the existing tractor pulley configuration.

Exactly what I did on my long gone Farmall A. I ditched the OEM generator and replaced it with a one wire GM alternator. Much simpler and less troublesome.

I'm guessing that means that the Farmall A battery was negative (frame) ground. Just sayin' because not all old tractors are negative frame ground.

And as I'm sure you know, the minimum number of conductors for any alternator is two, not one. In the GM the second "wire" is actually the conductive alternator case, mounting bracket, and connection to the frame (and battery) through the motor mounts.

 

[998cc]

Thanks for the replies. A few photos are attached. This new engine is a later model.

OK. It seems this "alternator" is barely up to the task. Can you just bypass the Kubota wiring and use any old alternator/regulator and go straight to the battery?

 

[DarkBlack]

I believe Kubota refers to them as a 'Dynamo' and it's basically a permanent magnet DC generator with minimal DC output. Problem is, the minimal output…

That dynamo is AC output, all day, from what the diagram shows.

 

[DarkBlack]

Thanks for the replies. A few photos are attached. This new engine is a later model.

OK. It seems this "alternator" is barely up to the task. Can you just bypass the Kubota wiring and use any old alternator/regulator and go straight to the battery?

You must have an external rectifier/regulator module in your tractor that converts unregulated 2 wire AC to regulated DC.
Almost all newer alternators include internally, rectification to DC, and also many have internal voltage regulation , so depending which you get , will determine if you bypass the original rectification/regulation

 

[Mike1955]

You must have an external rectifier/regulator module in your tractor that converts unregulated 2 wire AC to regulated DC.
Almost all newer alternators include internally, rectification to DC, and also many have internal voltage regulation , so depending which you get , will determine if you bypass the original rectification/regulation

I guess you could use a voltmeter to determine if it’s providing ac or dc.

 

[sd455dan]

I believe Kubota refers to them as a 'Dynamo' and it's basically a permanent magnet DC generator with minimal DC output. Problem is, the minimal DC output is insufficient to power anything but recharge a the starting battery and power a few lights. I would replace it with a one wire GM style alternator of sufficient amperage output to power what you require. One wire alternators are internally regulated so hookup is simple. Of course you will have to fabricate the necessary mounting brackets and match the drive pulley to the existing tractor pulley configuration.

Exactly what I did on my long gone Farmall A. I ditched the OEM generator and replaced it with a one wire GM alternator. Much simpler and less troublesome.

yep the venerable 10 SI, inexpensive and a big upgrade in output power even come in chrome for a good price if you want bling on your tractor or car.

 

[DarkBlack]

I guess you could use a voltmeter to determine if it’s providing ac or dc.

If it’s running and you’re there with a voltmeter, yes

 

[rScotty]

Thanks for the replies. A few photos are attached. This new engine is a later model.

OK. It seems this "alternator" is barely up to the task. Can you just bypass the Kubota wiring and use any old alternator/regulator and go straight to the battery?

Yes, electrically you can use any alternator/regulator pair that will physically fit. They all put out twelve volts. How much amperage (current) that they can potentially put out doesn't matter to the battery or the electricals in your tractor. The battery and electricals in your tractor will only take as much current as it can use.

All alternators makes their power when a magnetic field moves past a stationary coil - or a set of coils called the stator. The difference in low output and higher output alternators is in how they make that first magnetic field.

A small tractor or motorcycle alternator - often called a magneto type - uses permanent magnets in a spinning rotor to make its initial magnetic field. It spins that field past a stationalry set of coils. This type of magneto/alternator is small, lightweight and doesn't rob much horsepower away from the tractor or motorcycle when it is doing its work. It makes 12 volts or even more, but its amperage output is low.
A magneto type alternator can charge a battery while a small headlight or two are on, but not much more than that. Because it does not rob much HP to do its work, the pulley and belt can also be lightweight.
It's a nice fit for a little diesel tractor that doesn't need much electricity to run.

Cars and such use a heavy duty alternator doesn't have permanent magnets. It needs a more powerful magnetic field than magnets porvide, so its spinning rotor is actually a big coil wound into an electromagnet that is self-powered. This electromagnet is much more powerful than the permanent magnet type in a magneto rotor. With the big magnetic field and lots of heavy wire for multiple stator coils. This big modern alternator still puts out 12 volts, but can potentially put out much more amperage and can charge several batteries while also running heat/AC and multiple headlights on a car.
The downsides of that big car alternator on a tractor are it is large, heavy, and robs a lot of horsepower to do its work. Plus the pulley and belt have to be heavily built to handle the hp required by the alternator.

BOTTOM LINE: The sweet spot for your tractor is to use an alternator/regulator pair from a small imported car like a vintage Datsun. They are inexpensive and have the rectifier plate and regulator built right into the alternator body.

Hope this helps,
rScotty

 

[WranglerX]

Actually sweet spot is using a alternator that is internally regulated and one can eliminate external regulator....

 

[998cc]

Thanks guys.
One of my motorcycles runs an aftermarket permanent-magnet alternator and a combo rectifier/regulator unit, so I have some familiarity there. I like the idea of the "one wire" alternator for the Kubota. I'll suggest that. The owner has a well-equipped welding/machine shop at his home, so making a bracket is a simple process.

Regards to the group, and many thanks again.
Russ
B7100