Kubota generator starter remagnetize

[Murf2u]

Originally Posted by Midniteoyl

HAHAHAHAHAHA! What a moroon that guy is in the article!! Cant believe people fall for this stuff..

Apparently another "maroon" thinks the same way, the guy at Onan that wrote the service manual I have, it says;

"FLASHING THE FIELD

If the residual voltage is missing, it may be necessary to restore magnetism by flashing the exciter field. This requires a 12-volt battery, IO-ampere fuse, momentary on switch, and diode assembled as shown in Figure 4-2.

Field flashing can be done during generator set operation or when stopped. Either method should be sufficient to restore magnetism."

[Perry White]

Where's figure 4-2? help us out here.

[C-PHartley]

I have an Onan 7.5 KW generator with the Kubota Engine. I also had similar symptoms as the OP. The start button pulls the fuel solenoid for starting. I believe the circuit board senses 110 volt output along with Oil Pressure and Hi temp switch output. Any of these 3 areas can cause the fuel solenoid to drop out and kill the engine. I had to replace the circuit board to fix my problem. The board was available on the net for 1/2 the price I was charged by Onan. I hope this helps.

[bluepill]

Does “We the willing, led by the unknowing, are doing the impossible for the ungrateful" apply here?

[Midniteoyl]

Originally Posted by Murf2u

Apparently another "maroon" thinks the same way, the guy at Onan that wrote the service manual I have, it says;

"FLASHING THE FIELD

If the residual voltage is missing, it may be necessary to restore magnetism by flashing the exciter field. This requires a 12-volt battery, IO-ampere fuse, momentary on switch, and diode assembled as shown in Figure 4-2.

Field flashing can be done during generator set operation or when stopped. Either method should be sufficient to restore magnetism."

But, it is NOT due to the 'magnets losing their magnetism', as you say. Permanent magnets dont lose their magnetism, thats why they are permament..The field winding poles/cores are made of iron, and after the generator has been run a few seconds under load, will retain a weak magnetic field even after the generator has been shut down. This is the "residual magnetism". In some models/older models, residual magnetism in the generator exciter field allows the generator to build up voltage during start-up. This magnetism is sometimes lost due to shelf time or improper operation, among other reasons. Restoring this residual magnetism is possible and is sometimes referred to as "flashing the exciter field". In most models, a 12vdc source (such as the start batt) is used to excite the coils during start-up and when the genset starts to produce power, then becomes 'self exciting'.

Again, if you have to do this all the time, there is something wrong with the genset.. it is not 'self exciting' as it should.

[Murf2u]

Originally Posted by Murf2u

Apparently another "maroon" thinks the same way, the guy at Onan that wrote the service manual I have, it says;

Field flashing can be done during generator set operation or when stopped. Either method should be sufficient to restore magnetism."

Originally Posted by Midniteoyl

In most models, a 12vdc source (such as the start batt) is used to excite the coils during start-up and when the genset starts to produce power, then becomes 'self exciting'.

So you say 'most models' use 12 volts to excite the field coils, but Cummins / Onan tells you how to flash the coils, even with the unit off, to 'restore magentism'.


I think I'll stick with Onan's version.

BTW, in another section they refer to 'replacing magnets which have lost their strength and don't respond to restorative efforts'.

I guess their just making that up to sell more parts.

[Midniteoyl]

Google is your friend..

[Murf2u]

Originally Posted by Midniteoyl

Google is your friend..

Huh, you're right, Google is my friend. The first three sites (all companies that sell magnets) that Google gave me said this about 'permanent' magnets;

1) How permanent is a magnet's strength? If a magnet is stored away from power lines, other magnets, high temperatures, and other factors that adversely affect the magnet, it will retain its magnetism essentially forever.


2) Factors Which Cause Permanent Magnets to Lose Strength or to Demagnetize.


TEMPERATURE
Changes due to temperature effects fall into 3 categories

• Reversible losses
• Irreversible losses
• Metallurgical change

ADVERSE FIELDS
Exposing magnetized magnets to opposing external fields produces a demagnetizing effect. This effect is most apparent in permanent magnet materials having a non-linear demagnetization curve, such as Alnico. These adverse fields may be produced by current carrying conductors or by allowing magnets to come into contact with other magnets or ferrous material. The degree of the loss depends on the material characteristics. Other factors such as SHOCK and VIBRATION have very little effect on today’s permanent magnet materials. Unfortunately, most of today’s materials are brittle and crack prone, and must be handled carefully to avoid damaging the magnets.



3) Can a magnet lose its magnetism?


Yes, if a magnet is influenced by another strong magnet, is affected by a powerful electrical force, or is exposed to temperatures above a certain level, it may lose some or all of its magnetic strength.




So as long as the magnets in a genset installed in a m/h aren't exposed to heat, shock, vibration, other electrical forces, held in close proximity to other magnets or a host of other potential causes of degradation I suppose they would be 'permanent'.





However all of those are present in this case.

[wa8yxm]

I do admit that like many, some of whom it appears are in this thread, I always thought the magnetisim in the strator was permenate, And to a very very slight extent it is.

That is called "residual magnetism" and if the generator sits for too long without being run UNDER LOAD it can fade Plus there are some other related issues that are affected by sitting around dust collecting.

The reason this resigual magnetism is so limited is simple, there are two ways to control the voltage out in a generator.. ONE is to control the speed, lower speeds will generate lower voltages as a general rule (Given the same impedance load that is) however ... That is not a good way to do it, we need that puppy turning at a very fixed speed or downline stuff just won't work right.

The other way is to control the magnetism of the magnets, This is fairly easy, and how they do it. But if the resigual magnetism is too strong, then you can't control it.

I have heard about jumping power back into the generator before, From people I respect.

I exercise my generator .. Well once a month in the winter, every 2 weeks in the summer (need it for A/C)

As for how to re-magnatize.. Fill up the fuel tank, Crank that sucker up and make sure it's putting out 120vac, and plug in a space heater (Or two depending on the size of the beast) at least half it's power rating.. When it runs out of gas, odds are it will be good.