Good morning.
The cold storage temperature is -18 degrees Celsius. When the stepper motor is first powered on, it won’t turn under load. After removing the load, the motor can turn on its own, but it jerks. It runs normally after running idle for one minute and then reapplying the load.
I’ve changed the low-temperature grease (-40 degree specification) and also tried blowing it with a hot air gun before starting, which helped a little.
Could it be that old grease in the bearings wasn’t cleaned properly? Or is it that the resistance of the motor windings decreases at low temperatures, causing the driver’s overcurrent protection to activate?
Seeking experience with starting in sub-zero temperatures. Thank you.
Hi @Dominga ,
Have you stored the motors in a dry atmosphere? Are you operating the motors in a dry atmosphere? Any moisture present will freeze on the coldest surface. If that is the motor internals…
How did you clean the original grease from the bearings? You must never clean bearings in a ultrasonic bath. It destroys them. Pitting develops where the balls / rollers meet the races. If you can find them, buy the same size bearings pre-prepared for cold operation.
The best grease for vacuum cryogenic stepper motor applications is Castrol Braycote 601EF. It is VERY expensive, but, if your budget will allow, is the best choice for these applications.
There are scientific papers out there which may help, e.g. “Cryogenic Pick-Off Arms for VLT KMOS” by Richard Bennett et al.
I hope this helps,
Paul
Is running an isolated/insulated hot-line to warm the motor an option? Maybe using a ‘block heater’ for a car or electric blanket?