Speaking of generators......

[g-and-h_electric]

Are any of us here REAL familiar with brushless capacitor excited generators? I am working on an old 2 pole one that the rotor diodes failed. Easy enough to source and replace..... Here is the problem, I am finding conflicting wiring diagrams for the polarity of the diodes. The mfg of the genset (long out of business) shows them going in opposing directions, and a manual for the alternator shows them going the same direction.

Anyone here any experience with this stuff? Trying to get it running before the better half has me scrap it (she wants the patio back, I guess...)


Howard

 

[synchro]

Not sure exactly what you have, but if there are two diodes then you want them both to conduct current during one half-cycle, and both to block current during the other half-cycle. That assymmetic (half-wave) conduction creates DC current in the rotor winding. And so the anode of diode #1 would connect to one end of the rotor winding, and the cathode of diode #2 would connect to the other end of the rotor winding.

Can you post the two wiring diagrams?

 

[mbrooke]

Bump- I had this same question a few month ago.

 

[synchro]

Bump- I had this same question a few month ago.

This has a short explanation of capacitor excitation in such generators:

Newnes Electrical Power Engineer's Handbook

The second edition of this popular engineering reference book, previously titles Newnes Electrical Engineer’s Handbook, provides a basic understanding of the underlying theory and operation of the major classes of electrical equipment. With coverage including the key principles of electrical...

books.google.com

 

[Hv&Lv]

Are any of us here REAL familiar with brushless capacitor excited generators? I am working on an old 2 pole one that the rotor diodes failed. Easy enough to source and replace..... Here is the problem, I am finding conflicting wiring diagrams for the polarity of the diodes. The mfg of the genset (long out of business) shows them going in opposing directions, and a manual for the alternator shows them going the same direction.

Anyone here any experience with this stuff? Trying to get it running before the better half has me scrap it (she wants the patio back, I guess...)


Howard

I’m not but I tried to replace the diodes on one.
Actually did it twice on the same generator.
I also got conflicting information and tried them both ways.
Finally said some words I wasn’t proud of and junked the generator end. Sold the engine with no generator and got $400 for it.
I was surprised it brought that much.

 

[g-and-h_electric]

I was asked if I had the schematics..... Well yes I do! the first one is the schematic from the alternator manufacturer (MeccAlte , mod#MR2-200/2). The second one is from the gennie manufacturer (long out of business). I I installed the diodes like the MFG schematic shows, and no output. I am thinking the OEM drawing is correct, and as long as both diodes are going the same way, it shouldnt matter which way? Yes?


Howard

 

[LarryFine]

Are you talking about two separate 4-diode bridges like in the diagrams, or two individual diodes?

 

[Little Bill]

Are any of us here REAL familiar with brushless capacitor excited generators? I am working on an old 2 pole one that the rotor diodes failed. Easy enough to source and replace..... Here is the problem, I am finding conflicting wiring diagrams for the polarity of the diodes. The mfg of the genset (long out of business) shows them going in opposing directions, and a manual for the alternator shows them going the same direction.

Anyone here any experience with this stuff? Trying to get it running before the better half has me scrap it (she wants the patio back, I guess...)


Howard

Can't you look at the old diodes and see the polarity and how they are connected?

 

[g-and-h_electric]

2 single diodes at the end of the rotor. The bridge is for the battery charge circuit. As to figgering out the old diodes, there were no markings on them, and they were open.....

I am still thinking of following the OEM drawings.....


Howard

 

[synchro]

My comment in post #2 was assuming that you had one rotor winding.
The following document is for a later model from MeccAlte, but it may be similar enough to what you have. On page 6 notice that the cathode stripes of the diodes are both on the bottom. This means that when the rotor is turned 180 degrees their orientation relative the fixed stator is reversed. This is what you need because the opposite pole needs to have the opposite magnetic polarity as a result of the DC current through its local diode.

Winco_mecc_alte_port_ts_guide Winco Mecc Alte Port Ts Guide

User Manual: winco_mecc_alte_port_ts_guide

usermanual.wiki

 

[g-and-h_electric]

Sunchro ( and everyone else),

I think we have found the solution! I followed the "other" diagram (that came with the complete unit. Seeing as that arrangement didnt work, and the alternator co's manual differed, I figured I needed help!

Might be the weekend before I get to swapping diodes and testing, BUT at least now I know where to go.

I have reached out to the US office of MeccAlte and get the exact diode and MOV specs. I cant imagine the diodes being greater than 6 amp at 600prv......

 

[mbrooke]

This has a short explanation of capacitor excitation in such generators:

Newnes Electrical Power Engineer's Handbook

The second edition of this popular engineering reference book, previously titles Newnes Electrical Engineer’s Handbook, provides a basic understanding of the underlying theory and operation of the major classes of electrical equipment. With coverage including the key principles of electrical...

books.google.com

I'll see if I can find my thread.

In any way, thanks!

 

[synchro]

Might be the weekend before I get to swapping diodes and testing, BUT at least now I know where to go.

If you connected new diodes and it didn't work, did you try "flashing" the generator? That might be necessary if there's not sufficient residual magnetism in the rotor for the generator to "bootstrap" itself. If you're not familiar with this you can search online for the various ways of doing it.

 

[g-and-h_electric]

I have the diodes currently going in opposite directions.... not going the same direction... the alternator mfg's manual was correct, based upon the manual and pics you posted. I had installed the diodes based upon the manual that came with the unit.... with manuals like that I can see why they arent in business anymore...


Howard