SolarMechE
Mechanical
I work on a tracking solar concentrator system that currently uses a small (NEMA 17) stepper motor for our actuation. This product is a rooftop system that will be exposed to the environment. We are hoping to achieve a 15-year maintenance-free lifetime for our product. Our duty cycle is extremely low (something like 180 degrees of motion which, depending on the gear train we end up with, will probably correspond to around 15 revolutions of the motor, taken in small increments spread across the daylight hours) so this requirement is hopefully attainable.
My question relates to testing that we can perform on the motor to gain some amount of confidence that it will last this length of time. This accelerated testing should hopefully cover both environmental and functional tests. I understand that performing functional tests like this is fairly common. We can do things like overstress the motors and run them constantly to try to simulate 15 years at our duty cycle. What I am struggling much more with is accelerated environmental testing. I've read through documents such as mil-std-810f which suggest different testing regimes; however they give no details about what it means to pass those tests. Does surviving the 810f humidity cycling test mean the motor will survive 5 years (or 10 or 15) of service life? I realize there is probably no direct correlation like this, but is there some theory out there that helps to predict this kind of thing? I've also heard that salt fog testing is a very extreme test to put something through, but again, what does it mean to pass salt fog? Does surviving 48 hours in a salt fog chamber tell me something about the expected lifetime of my product?
Any information or links to information about accelerated testing, both environmental and functional, specifically related to motors, would be greatly appreciated.
My question relates to testing that we can perform on the motor to gain some amount of confidence that it will last this length of time. This accelerated testing should hopefully cover both environmental and functional tests. I understand that performing functional tests like this is fairly common. We can do things like overstress the motors and run them constantly to try to simulate 15 years at our duty cycle. What I am struggling much more with is accelerated environmental testing. I've read through documents such as mil-std-810f which suggest different testing regimes; however they give no details about what it means to pass those tests. Does surviving the 810f humidity cycling test mean the motor will survive 5 years (or 10 or 15) of service life? I realize there is probably no direct correlation like this, but is there some theory out there that helps to predict this kind of thing? I've also heard that salt fog testing is a very extreme test to put something through, but again, what does it mean to pass salt fog? Does surviving 48 hours in a salt fog chamber tell me something about the expected lifetime of my product?
Any information or links to information about accelerated testing, both environmental and functional, specifically related to motors, would be greatly appreciated.
