Kraft & Dele KW 6500 Generator: AVR Regulator Damages, 3-Phase Issues, Replacement Options

boras_ptu wrote:

A colleague has a self-excited generator without AVR, and here I would look for the cause.
Residual magnetism does not disappear by itself.

This is not true, the generators with AVR are also self-excited, and the AVR only regulates the voltage value. Residual magnetism, as colleague GFM wrote, depends on the magnetic properties of the rotor material. In this case, neodymium is added to strengthen this magnetism. This is the case with my aggregate, to which, after a little modification, you can add AVR.
Rotor photo, which was included in col. smerdendes in his post, it is from the generator with AVR and you can also see a magnet (probably neodymium) on it. The description of the problem suggests that there is not enough residual magnetism to excite. The description shows that after excitation of the generator from a foreign source, after stopping the generator, the magnetism quickly weakens. But I also do not exclude the fact that the reason may lie in the AVR itself, that it causes a break in the excitation circuit during a longer standstill, which should not be in this state.

Nobody wrote that AVR generators are not self-excited !!!
You can safely say that 99% of currently sold low and medium power generators are self-excited.
Magnetism decay is a long process and the magnet is there to excite the generator from the first rotation of the rotor. My guess is that no one was bothering my colleague's generator - and if so, I would check the voltage polarization connection on the brushes.

I will just add that the crap that I have is not used since it was new, but it has been in stock for over 5 years, so there is an option that the magnets have demagnetized ... Electrically everything is ok, the resistances are correct and the voltage is also correct (after excitation with the specified voltage on the brushes)
At the moment I have ordered a few small neodymium magnets and when they come, I will try to fit them somewhere in the rotor.
On the back it looks like in the attached photo.
When the magnets come, I will write what came out of it, maybe someone will need this knowledge ...
Thanks for the replies. Regards.

Got a new AVR today and I'm happy now. in 5 minutes mounted and adjusted to the correct voltage. Everything works as it should. Yes, as I suspected - cheap universal replacements are not always OK. Only the third one worked for me - in the ALU housing and "supposedly Polish" - I do not penetrate, it works again and this is the most important thing. I did not try to resuscitate the old one - scraping for PLN 36 (with delivery) will not pay off.
Thanks to everyone for the hints and comments.

The magnets came, however, they were not able to be screwed to these screws on the side of the rotor because they are too brittle and broke when I tried to tighten it more, but when I removed the stator, the rotor magnets are in place and seem to be OK, they normally attract a screwdriver ...
In the meantime, I also bought a new AVR regulator and after putting it on, the same thing, i.e. it turns on when low voltage is applied to the brushes from the outside. When it turns on, all phases have the correct voltage and can be adjusted using the potentiometer in the AVR ...
I have no idea what it is about ...

Were it not for what you wrote earlier that after a short standstill, the generator excites normally, one would suppose that the magnetic field of the magnets on the rotor is opposite to the field that would be generated by the excitation current and therefore does not self-excite. When you apply tension to the brushes, this field is dominant and excitation occurs. Only in this situation, after turning off the drive motor for a while after restarting, there should be no self-excitation - it seems to me.
Nevertheless, I would try to start the generator with the wires on the brush holders changed and check what effect it will give.

I will not combine the polarity change for now, because something else will get hot and it will only be ...
I sent back this `` new '' regulator and asked for another one. Apart from the fact that it did not work, it could not be screwed with two screws, the hole spacing was slightly different. I will give it one more chance, probably the last one.

Nothing should burn out to me, but you decide.

As easy as possible
There is a moment in the generator's operation (at start-up) when the magnetic field from the rotor (supported by magnets) produces a current in the stator coil, which supplies the rotor via AVR, the rotor then creates its own field, and both fields have the same value.
The polarity of the brushes is so that these fields add up, not cancel out. If the polarity is incorrect, the magnet has a constant power and excites the generator until the incorrectly polarized rotor field reduces it to zero. If the polarity is OK, the fields add up and the generator turns on.
When the rotor is temporarily powered by an external source, the rotor field is so large that the magnets cannot reset, so the generator works and the AVR supplies enough current to reach the reference voltage set with the PR at the output of the control coil.
Changing the polarity will not damage the generator - it will not work any more.

Another regulator came, supposedly checked and still the same, changing the poles on the brushes also did not help. I decided to try to put on the old, original regulator and something strange happened, the generator is normally energized at each start, but the voltage on each phase is almost 300V and The regulation of the controller on the regulator does not give anything ... and the brushes go almost 150V .... Now I don't understand it anymore. The customer from whom I bought gave me a phone number for their service, I will try to call there tomorrow and I will listen to what they will tell me.

I had exactly this symptom. 350V at the output of the generator and constant excitation over 100V. Changing the AVR solved the problem.
I bought here:
allegro: 7941798949. It worked.

I see that I bought in the same store .... For now, I will send a third piece and we'll see what's next ...

Apparently I was lucky enough to get working art the first time.
From what I remember (because I will not dismantle the generator anymore), the AVR (control voltage from the main winding tap) is about 18V. The additional winding (for the AVR power supply) is about 110V, the rotor power supply (for the brushes) is 24V.
For me, with these parameters, I have 230V at the output of the generator.

Make another test like this:
- check if there are any breaks to ground and the resistance of the working windings if they are symmetrical (disconnect the AVR from the control tap)
- give 24V brushes from an external source (of course, according to the polarity given on the brush holder - the only constant voltage)
- start the generator and measure the voltage at the output of the windings: (auxiliary, control AVR and all main ones) As they are in the area of what I wrote above - only the AVR remains.

PS. Some models still have a 14V winding connected only to a rectifier bridge.

Added after 6 [minutes]:

Oh - and one more note,
I read that all AVRs for these Chinese generators up to 2kW are exactly the same and differ only in the capacitor and housing.
Don't look at the price because "more expensive" does not necessarily mean "better".

However, the saying goes up to three times a piece. They sent it this time in a black, plastic housing and it finally moved, it even fits the mounting holes. I wonder how long it will take ....

I have a similar problem, except that out of 5 controllers, 1 worked for a few minutes and the rest did not work at all. If I connect a 12v battery, I get approximately 250v.
I don't know what to do with it, should I buy regulators until I get it? Could there be any other reason for it not working?

Hello, I have a question for the author. How did a colleague get this black resin out of the avr?
Greetings!
.

About the removal of the black mass, how I dealt with it, I wrote in #21 post.

Thanks Gimak ! Sorry I didn't read carefully