Small AC Generator Three Phase

Yo guest As far as I can get out of your message there is something wrong with the rectifying circuit of the exitation coil. We used to give then an 12 or 24 v batteryimpuls as well on our generators until we had the spareparts So you need to check the rectifier , this can be a little circuit of Zenerdiodes or a complete rectifier. It looks as if it's leaking towards earth or is loosing power trough one of the Zeners. To place a temp supply towards your exitation coils is quite good as long as you give only a short impuls. Good luck T L.

hi, thanks for your reply

its three phase full wave rectifier, i already checked the six diodes with multimeter and the were ok, now how can i know if its leaking to earth?... or should i just buy new bridge rectifier and give it try!

actually, this engine is hand cranking, so if i will use the second solution, i need to buy battery and but it beside the generator, and sure i need to take it for charge from while to another as there is no alternator fitted on the engine.

so its quite un preferably.

thanks

Yo

The diodeplates are supposed to be totally insulated from earth / chassis if not you have a shorting there

Did you try to measure the resistance of the exitation_coil and it's leads (separated from the rectifier) towards the chassis ?

It should read more then 20 meg Ohms

Further it's also possible that the exitation coil has an internal short circuit, hence the low voltage and the overheating resistor.

You didn't mention the brand/type of the generatorset

So give me that too, maybe I can check how high the internal resistance of the coil has has to be.

Good Luck

TTYL T L.

hi,

sorry for late reply

i checked the resistance of the rotor coil and it was 53 ohms, i tested with megger and it was more than 20 meg ohms.

the engine is lombardini, but i could not read on the generator side as the name plate is gone.

thanks

Hi again ,

No prob, time is irrilevant

So the resistnce of the coil is good and insulated.

pls check also the rectifierplates first against earth/chassis

then against each other ,so the 2 sets of 3 diodes ,

check their resistance , invert the test leads and check again.

see that you get appr. the same reading for one diodeplate to the other.

if there is a substantial difference , then you could check each diode separately.

then you might have to purchase 6 new ones or equivalents.

further I can see at the moment is loss of residual flux as you yourself mentioned before.

Gino AG

Check tab Gino excitation resistors

Tried Lombardini sets alas only new type and no diagrams. (not yet, my Google A.I. checks on )

In the meantime good luck with testing and hand_excitation

L8rz.. Ciao T L