Onan Generator

Does your generator have a regulator board?

It sounds like that could possibly be your problem.

Is this load shedding across all three phases? What are you reading phase to neutral for all phases?

An example of a quality product. The YD's were among the best.

From your OP you say this is supplying crushers and conveyors. 30KVA seems very low for a duty that by its very nature is liable to overload.

To be honest, I think this last plant blockage has been the straw that broke the camels back.

RIP Onan generator.

Once you've replaced the generator it seems you need to review and make immediate improvements to the way that overload and short circuit protective devices are coordinated across the facility, Mildred. If smoke has come out of a motor then something is seriously wrong that will, if unattended, make your fire insurance company very angry with you!

Looks like the overload at the conveyors wasn't seen and tripped early enough. Best to set overloads a s low as possible, just on the full load current of the motor so no chance of smoking. There are devices to detect over temperature which can be retrofitted and trip the starter before any fire.

The Onan Genset. There's coil on the rotor part which has brushes, this can be checked for continuity and insulation. Then the generator coils around the stator part, these may be starred at an inaccessible point or you may be able to separate the three windings and check each one. This will show if any windings have burned up, then you have to decide. Personally I'd go for a bigger set and scrap the old one so you have ample capacity in any future heavy loading which you do get in quarrying as stones get jammed. Depends what a shutdown is costing you.

"A sound like when something new is turned on would momentarily come from the generator and then no more power at the breaker." ????

I think he means the humming noise from a power source when you attach a heavy load; which in this case is not sustained due to generator failure ( likely burnt/loose connections or bad winding ).

Any odours from the generator winding ?, use a megger to check insulation and an ohmmeter to check winding resistance; look for charred wires and overheated signs at every connection terminal from the alternator, all the way to the loads.

Thanks everyone, I am heading to the mine early tomorrow and will check it out as best I can. Thanks SolarEagle for the manual it will certainly help.

I could not find anything that was obviously wrong with the Onan. For now I will set it aside and comeback to it when there is more time to troubleshot.

I also have a diesel 60 to 70 kw Kohler. However I'm having trouble starting it and then to provide the 480 v we need.

It has set for a while, more then a year without running. I am told that the magnetic field relating to the exciter may be dead or needs a 12 volt boost of some kind to get it going. I am totally out of my element here.

What I do know is there is a toggle prime switch that was momentarily held down and then you would push the starter switch until it started. You would need to push and hold it in for 30 to 60 seconds or more and then it would start and run. Until then no sound (except the operator complaining about holding in the switch).

Now there is no starting at all regardless of how many times and for how long the switch is held. I was able to start it by jumping the small solenoid in the control panel. Just a touch and it immediately roared into action. However, no 480 v produced. Across any two leads it showed only 12 volts and after 5 minutes it shut itself down.

There were 3 small fuses just inside the front of the generator cage but they read good. Should someone be able to provide some insight it would be greatly appreciated. Thanks again