Smoked brand new diodes - GETT / Applied ECU / 23kw 3 Phase Generator

[gotaconvoy]

Unit:

Applied Companies 23kw 3 phase genset / 120k btu ECU trailer

Trailer tags:

GETT Trailer Assembly (17v) 1vpw8 (1p) 01-p54234e001
Applied Companies 23kw generator, part # 52480, model # 20RFH33DWLP

Generator identifiers:

On the alternator / genhead: SWP southwest Products / HANCO Generator Systems - Model 20RFH33DWLP
On the other side of the alternator / genhead: Creazzo Vicenza Italia - Type ECO 28-2L/4


Issue:

I've been diagnosing a no-power-production issue for a while now. The diesel runs great, but the alternator never made any power. I tried flashing the windings and installed a new AVR. I then pulled off the side cover and found 6 physically damaged diodes on the rotating assembly. Mecc ALte is the only supplier of these diodes and $242 later I had 6 of them delivered.

I installed the 6 diodes this evening and fired the generator up in accordance with the instructions (no load). Within 30 seconds the diodes were glowing/sparking and I shut the unit down immediately. Subsequent inspection shows the brand new diodes have physically burned up.

What can cause this?

I should note that I installed the diodes in the direction/polarity I *think* they go (all stripes on the right side), but I was unable to find any actual information that 100% confirmed the install direction.

Any ideas?

 

[MrMikey4026]

Shorted rotor.

 

[98G]

Shorted rotor.

That sounds ominous...

 

[gotaconvoy]

Shorted rotor.

That doesn't sound good. What's the remedy?

 

[Triple Jim]

Just for reference, what are the part numbers of the diodes?

 

[gotaconvoy]

Just for reference, what are the part numbers of the diodes?

Mecc Alte would not give that up. They also would not give any of the specs on them, and when they arrived they showed up in a clear plastic baggie and have no markings on them aside from the band on one side. I spent a considerable amount of time trying to find diodes that did not cost $27 a piece because that's ridiculous. But I failed and had to buy them only to watch them turn into a puff of smoke in 30 seconds. Haha

 

[Guyfang]

Could be a shorted rotor. Could be you installed 2 or more incorrectly. This is not going to be a simple fix. I would pull the Main gen and start testing each component.

 

[gotaconvoy]

The mecc alte rep just sent this 700+ page manual. I'm hoping there's some troubleshooting flowcharts and/or various specs that I can start pouring over.

I see on page 45 that it appears I did install the diodes in the correct polarity. Which makes sense because when I acquired the generator, the diodes were already burned up. So something made the diodes burn, they did a quick diagnosis, then dead lined the unit and eventually actioned it off.

If anyone's got any ideas I'm all ears. I'm new to generators and am learning as I go.

https://www.meccalte.com/downloads/iManual_ECO_ECP_rev03.pdf

 

[87cr250r]

Here is a short article on diode failures. It sounds like your exciter is damaged. I would suggest taking a resistance reading on the exciter.

Diode Failure Scenarios Modes of Failure, Causes and Effects - MER Equipment https://merequipment.com/wp-content/uploads/Diode-Failure-Scenarios.pdf

 

[gotaconvoy]

Here is a short article on diode failures. It sounds like your exciter is damaged. I would suggest taking a resistance reading on the exciter.

Diode Failure Scenarios Modes of Failure, Causes and Effects - MER Equipment https://merequipment.com/wp-content/uploads/Diode-Failure-Scenarios.pdf

Thanks for the info!

To clarify - the exciter is the same as the rotor/rotating assembly? I'll have to do some research but I' assuming if I remove the diodes again, I can take resistance reading in place of the 6 diodes and look for a dead short?

 

[Triple Jim]

The exciter armature and the diodes generate the current for the main generator's rotating field. Those parts make up the rotating assembly.

The exciter field is stationary, and the regulator controls the current to it. The exciter's output from its rotating armature and diodes are connected to the main rotating field. The actual generator output comes from the stationary armature. This allows the generator to work without brushes or other means of commutation, since both control current and generator output are connected to stationary windings.

 

[gotaconvoy]

Ok, I ordered a 'megger' insulation tester and should be able to spend some time on this in a few days. I'm going to research exactly how to do the test and what readings I'm looking for, but any tips or pointers would be greatly appreciated!

 

[87cr250r]

The megger is for condition monitoring, not troubleshooting. You start with a new set and when the reading drops below a certain value you send the windings out of a bake.

If you're blowing diodes your resistances are already in the ohm range and can be tested with a standard ohmmeter.

Also note that meggers can damage diodes so the diode ring needs to be disconnected prior to a megger test on the field widing.

 

[gotaconvoy]

The megger is for condition monitoring, not troubleshooting. You start with a new set and when the reading drops below a certain value you send the windings out of a bake.

If you're blowing diodes your resistances are already in the ohm range and can be tested with a standard ohmmeter.

Also note that meggers can damage diodes so the diode ring needs to be disconnected prior to a megger test on the field widing.

Oh, the current diodes are ashes. haha.

So where am I taking these resistance readings? I assume across the various windings? Looking for continuity to ground?

 

[87cr250r]

If the generator is wired you need only measure one lead to ground as all leads tie together. Do lift the ground connection if present.

If you have a 6 or 12 lead generator you can measure each coil individually.

Measure you armature to rotor winding resistance.

Measure your armature winding resistance.

Measure your l field coil resistance

Measure your field coil to ground resistance.

Stator resistance to ground and coil resistance are fairly universal but field winding and armature valves will vary by make.