Kato AC Generator leads identification 1

[ingcalderon]

Hi how are you all?, ill appreciate if you can help me, i have a kato Ac generator that the leads were cutoff and i dont have any identification. Dont know if there is a method for identifying wich group of leads makes each phase.

The generator stator is a 6 parallel group with 6 leads per group total of 36 leads. I can identify through continuity each coil, and have read some methods here that exciting with AC voltage the rotor and rotating then i can found each group, but its not very clear to me.
thanks for your help,

 

[waross]

First megger the leads to see if the insulation is in good shape. If the leads were cut off because the generator had failed you are wasting time trying to identify them.
If this is a three phase generator:
Note: If the set is above about 15 KVA, it is probably a three phase set even if it is marketed as a single phase set. Above about 15 KVA it is common to reconnect three phase sets for single phase applications.
When a rotor pole is stationary directly under a stator pole you can use transformer action.
Apply a few Amps AC directly to the field coils. If this a brushless set you will have to disconnect the rotating diodes and connect to the field with long leads. Leave enough slack to allow a couple of revolutions of the rotor.
Find a pair of leads and rotate the rotor until you read the maximum voltage across the pair. You should now be able to locate two other coils with similar voltages.
Congratulations, you have just identified one phase. Label all these as A phase.
Now turn the rotor 120 degrees and look for three more windings.
Label these as B phase.
Another 120 degrees and find C phase.





Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ingcalderon]

Thanks for your prompt answell Waross,
yes its a 1000 kW three phase Ac generator. its brushless it has PMG excitation.
The insulation its ok, it was cut off maybe they stole the wires for selling cooper.
Few Ac amps, will be with 110 AC or less voltage ? i have a variac. the AC voltage should be applied directly to wires that goes to the rotor or to the (+) and (-) of the exciter stator wires (from AVR)?

The rotation its by hand right , until i get the peak voltage in a coil and them for the rest of the coil groups for having phase A.
Then from where i stopped the rotor i rotated it 120 degrees and to the same for another group of coils right this is phase B and them the same for phase C.

thanks for your help.

 

[waross]

You are on track. The AC has to be injected into the rotor winding directly.
If the AC is connected to the (+) (-) wires from the AVR, the rotating diodes will rectify the current to DC before it gets to the field windings and there will be no transformer action.
The rotation is by hand.
Once you have identified and numbered the coils as A, B and C. come back and we will give you instaructions as to connecting them in the correct polarity.
I suggest numbering Phase, group and start-end.
The leads of first coil in A phase will be numbered A1-1 and A1-2 The second coil will be A2-1 and A2-2,
The next A3-1 and A2-2 and so on.
In the next step some of the numbers will have to be changed..
eg: A2-1 and A2-2, may become A2-2 and A2-1.
Be slow and careful. It is easy to become confused and make simple mistakes if you let yourself become rushed.
Waiting to hear from you.
Bueno suerte.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ingcalderon]

Thanks a lot, you have been very helpful.
Ok i will start identifying the group coils and once i finish ill let you know so i can continue with identifying the polarity.

Muchas gracias!.

 

[ingcalderon]

Hi Waross how are you?,

i did the following: with the Variac i sent 120 Vac directly to the rotor, then i took the voltmeter and took a random coil and marked it as A11 and A12 and turn the rotor until i got the max. voltaje (1.3 Vac), and stop there i identify 5 more of coils and then rotate and identify the B and C phases, also only 1.3 Vac output with 120 Vac input.

can you please tell me what i have to do from here for finding the polarity.

thanks,

 

[waross]

Easy;
connect A1-2 to A2-1 and measure the voltage from A1-1 to A2-2. If it is about 1.6 volts it is good.
If it is zero volts change the numbers on A2. A2-1 becomes A2-2 and A2-2 becomes A2-1. Reconnect and recheck the voltage.
Then go to coil A3-, A4, A5, and A6 and do the same thing.
Repeat for the other two phases and then check in again for the next step.
Just to recheck, did you disconnect the diodes before starting?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ingcalderon]

Again thanks for your help, yes the rectifier bridge its disconnected, actually i did it without having installed the stator and rotor of the exciter.

When i do the jumpers between a1-2 and a2-1 the induce voltage must be in the rotor wires as well as i did on the coil i.d? Apply the same 120vac.
Regards

 

[waross]

Yes. You need to generate voltage in the coils to check the polarity.

Bill
--------------------
"Why not the best?"
Jimmy Carter