Re: G3406 undervoltage at only 50% load

The voltage remained stable. It was more of Engine issue than Generator. 

We have been able to diagnose the issue and the engine RPM were droping due to supply gas. Fuel gas was mixed and the ratio was changed which caused the engine to behave abnormally.

Thanks for reply


Trusted Contributor
Trusted Contributor

Re: G3406 undervoltage at only 50% load

Does the engine speed drop when you apply load above 50%?  If the engine speed remains stable, the issue sounds like a generator issue instead of an engine issue.  If the engine speed is dropping with added load, this will cause the generator output voltage to decrease.  If this is the condition, then you need to determine why the engine speed is dropping.  Fuel supply pressure decreasing?  Governor working correctly?  Carburetor issue?  Turbocharger or wastegate issue, if equipped with a turbocharger?  As the load increases, the wastegate must stay closed to allow the turbocharger to build up boost to make the required horsepower  to carry the load.


If the engine speed remains stable, the low voltage issue could be the generator regulator not maintaining output voltage as the load increases.


Best Regards,

Al Hunt

Accepted Solution

G3406 undervoltage at only 50% load


Our Natural Gas operated G-3406, 159KW engine is giving undervoltage dips above 50% load. Few days before, it was running normally upto 80% laod, but now as soon as load crosses 50%, the voltage drop to 320V and the engine give abnormal sound.

No changes in supply gas specifications or pressure carried out. Any suggestions are appreciated plz