New member

Re: Recommended Percentage Load on Cat 3512 Generator

Working on a land rig with 4ea 3512C's driving a VFD system, we currently run our engines at 75-85% load, not only does this help with diesel consumption (less engines on line) it seems to help with engine life cycle parts (turbos, coolers) our VFD drive system helps a lot with the mentioned load sharing, cyclic loads.

Working conditions are fairly harsh (hot) with extreams as high as 41-45C and we have not experenced any shutdowns due to overheating.

Super Contributor

Re: Recommended Percentage Load on Cat 3512 Generator

Something you may need to consider, what is acceptable for a maximum engine/generator load may not be what is acceptable for the "system". Does the requirement of not operating the units over 50% of rated load come from the need for capacity in the event of a transient condition?. Drill rigs have VERY cyclic loads, without knowing the actual load profile of your particular drilling system, hard to determine what the actual reserve capacity requirement is.  If you don't have the capacity on line when a large load change occurs, then you could trip the power supply and really cause problems. 


In reality, most rig opreators are extermely conservative, keeping maximum capacity on line to assure the least possibiltiy of tripping the power system off with pipe in the hole. Yes it's wasteful, and unless there is a good ballast load system, hard on the units as well, but those operating the rig have to deal with all the risk issues, and in many cases running generator sets far below rated capacity is considered acceptable, or at least the lesser of all possible evils.


As engine people we would like to see engines, especially newer design engines, run at higher load factors to assure best possible performance and service life, but some operations just don't allow for the best situation for the engines.


Hope that helps, Mike L.

Trusted Contributor

Re: Recommended Percentage Load on Cat 3512 Generator

drilling application engines are usually sold as prime power and therefor can run 100% electrical load unrestricted.

100% engine load will be 110% electrical load, usually not longer allowed then 1 hour continous. 


New member

Recommended Percentage Load on Cat 3512 Generator

I currently work on a drilling rig were the drilling contractor uses four Caterpillar 3512 (1500kva 1020kw ) Land Electric Drilling Package diesel generators to power the rig.


The load on each generator is not allowed to exceed 50% of rated generator's load capacity. I find this unacceptable and wasteful on diesel.



If the load on each generator could be higher, fewer generators would be required, thereby saving diesel. 


I would please like to know what the recommended maximum percentage loading is on this model of generator




NB: Outside temperature in the day usually ranges between 29degC to 32degC.