why cold motors don't run?

[Gaston]

We have some 24 vold dc motors at work that when they get too cold they wont run untill they warm up. Why would they not run? I thought conductors conducted better in the cold. And i don't think its the lubricant getting to viscuous because they still turn freely by hand

 

[dknguyen]

We have some 24 vold dc motors at work that when they get too cold they wont run untill they warm up. Why would they not run? I thought conductors conducted better in the cold. And i don't think its the lubricant getting to viscuous because they still turn freely by hand

How cold? Everything has an operating temperature range. COuld it be the motor controller? MOSFETs don't work when too cold. Or is it just a battery? Maybe the lubricant is too viscous so the motor can't turn over, even if you can turn it by hand.

 

[Gaston]

there are no mosfets just some TIP's i don remember the number though. its powerewd by a power supply and everything else works. i pretty sure its the motor because there is an optional heater that blows right on the motor

 

[justDIY]

mosfets don't work when it's too cold? I think the lubrication would freeze solid long before transistors stopped working.

taking a quick peak at the datasheet for the IRF3708, the operating range for the junction (Tj) is listed as -55C to 175C. I'm guessing they stopped at -55C because of problems with glass transition in the epoxy package or the metal bonds becoming too fragile to be mechanically reliable?

 

[dknguyen]

Something about the carrier mobility decreasing as temperature decreases. But that doesn't make sense considering MOSFET resistance rises as temperature increases.

I've just know that I have heard stories about MOSFETs not working in winter temperatures (or at least not as intended). I could be wrong.

 

[crusty]

well if they're AC motors the stater cap might be going bad, i would assume this to be more of a bearing and lubricant issue. lubrication loves to thicken with age and colder temperatures, might want to squirt a lil bit of penetrating oil like WD40 on the grease every once in awhile to keep the grease from drying up on you.

 

[justDIY]

Something about the carrier mobility decreasing as temperature decreases. But that doesn't make sense considering MOSFET resistance rises as temperature increases.

I've just know that I have heard stories about MOSFETs not working in winter temperatures (or at least not as intended). I could be wrong.

I agree they probably have a lower limit somewhere, but I don't think it would be a temperature commonly found in the real world.

Look at extreme over clocking, CPU's are submerged in LN2 and still operate - they contain millions and millions of mosfet gates... or what about radio astronomy - super sensitive amplifiers operating while bathed in LN2 or even colder, LHE to keep the heat noise level down.