There are lots of variables that impact on the life of a VFD but 10 years is a good number to start with.
If you have them in a clean cool environment and are well installed and maintained you will get longer.
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
NPV? Net Present Value? If so, you would need to factor in all of the lifetime costs and the typical MTTF/MTBF of good quality Voltage Source Inverters (as almost all Low Voltage drives would be) is going to be 100,000 hours (about 11 years). In reality however a major component in them, namely the capacitors, are commonly over stressed and fail after about 7 years. Technically you could add an additional 50% of the current cost to replace the caps after 3/4 of the VFD lifespan, but the reality will be that by then, the newer technology drive will be less expensive than repairing the old one, it almost always is. So I just tell people to use 7 years as the expected life of the technology and if you get more, it's a bonus.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
Also worth considering that a 10K reduction in capacitor temperature will normally double their lifetime. So some thought about cooling, etc. could save a lot of money in the long term....
Cheers,
Mort
