Fan life vs temperature

[Circlotron]

Some time ago we had to do accelerated life tests on some brushless DC cooling fans for use in a 3kW SMPS. Rigged up a hotbox with two large globes as heat sources, and a thermostat to regulate the temperature to 75 deg C. Some of the fans quit after only several thousand hours, even so-called long life ones with ceramic sleeve bearings. We had a couple of Sunon 90mm ball bearing ones in the mix as well. At the same time I thought I'd try a low temperature life test as well. Put one of those same Sunon fans in the fridge at home, also for the purpose of increasing the efficiency of the evaporator and making the temp more even throughout the fridge. As an aside, with a fan also on the condenser at the back, the compressor duty cycle dropped from 60% to 31%, averaged over 2 years. Anyway, I put the fan in the fridge at 4 deg C ambient on 2nd November 2002 and it is still going today, running 24/7. That's 118,000 hours and it's showing no signs of giving up. 2020? We'll see :-)

[Richard Head]

Lifetime vs ambient temp is available in the EBM/Papst catalog. For Sunon I have never found adequate lifetime data so avoid them. Small fans = short life. Big fans = long life.
I've done environmental tests to -55 deg C and the fans stop at about -18 Deg C. The bearings starts to seize up. Raise the temp and all is ok again.