How to megger a 80 DGDA Onan Cummins generator

[cvargas345]

I need help on getting some information on how to megger the stator windings on the above mentioned model generator.

Thank you

 

[asekhar]

I am not sure what you are asking. If it is how a meggar testing is done, I have explained below.

Meggar is basically measurement of insulation resistance of the machine. The meggar leads are to be connected between the terminal & earth and the readings noted. Obviously, it is done with the machine isolated. Incase the neutral is connected to earth, either directly or through a neutral grounding resistor, that needs to be isolated before the testing. The insulation resistance value will stabilize in few minutes. If it is a big machine the reading is taken over 10 minutes. Small machines, even 1 minute readings can be considered sufficient.

Depending on the voltage rating of the generator, the meggar voltage will vary.

Hope that answers your question.

Anand Sekhar

 

[waross]

From the hands on point of view;
1:> disconnect the grounding jumper if present.
2:> Disconnect the Automatic Voltage Regulator leads.
3:> Disconnect the wiring to the panel meters (Voltmeters, Power Meters and anything with a voltage connection.
4:> Consider disconnecting the leads to the main circuit breaker.
5:> There should be nothing connected to the windings except other windings, and possibly the main breaker if that is your choice.
You may megger the windings as a group, or choose to megger them individually. Group checking is fast. Individual checking may show up a winding with a much lower resistance to ground than the others even though it is acceptably high. The choice of methods depends on the reason for the test in the first place.
respectfully