cold starts on electric motors?

soundmind

KNIFE MAKER
Anyone have advice on how cold weather can affect electric motors? I was thinking cold starts are ok around 20-30 above zero. I think about 10 above would be my cut-off and anything below that I'd be warming up the electric tools first.

Also, does anyone have experience with temp fluctuation causing moisture to buildup in the motor and wear it out faster?

Thanks for the help.
 
cold starts are not an issue. if the shaft will turn then it will make enough heat for the bearings to lubricate themselves in just a few rotations.

moisture can cause issues with very large motors and generators. Big units have heaters in them. That said, the small HP units we use in a shop are fairly unaffected. A 1HP TEFC motor is going to die over time as the insulation breaks down or the bearings fail - long before moisture or cold temperatures have any effect.

I have poured water out of motors that lived in the worst environments you can imagine. They tend to fail because the bearings disintegrate.

Think about every swimming pool out there. The pump motor lives outside in the rain. They rust away before they die electrically.

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That makes sense. If the shaft is able to turn and bearings are lubricating, then I don't see why any condensation shouldn't burn off right away, too.

Not sure, but it seems like I need to make sure I'm using them in order to keep condensation in check?

Luke
 
Condensate inside of a motor primarily comes from cycling the motor on and off in an extremely humid atmosphere. You'll get condensate in a motor, say on a boiler flat or in a pump room of a factory where the ambient temperature is 110 degrees with 90 percent humidity. You'll know, because every metal surface in the whole place will be wet and rusty. It's the kind of room you walk into and get immediately filthy just standing there.

Even in such an environment, your $200 motor will last several years until the bearings rust out and the grease dissipates from the bearing. That is what kills motors. For every motor I've ever replaced where the windings shorted or broke down I have replaced 20 times that amount because the bearings failed. On little motors (less than 5HP) you're only going to find sealed bearings anymore. When the bearings fail, the motor stops. It's not even worth replacing bearings on a small motor. You chunk it and put in another one. Once you get to 5HP or so it becomes worth the effort to replace bearings. If the motor has a cast iron frame (it looks like it has big fins all over it) you can replace the bearings. If the motor is a rolled steel frame (looks like a coffee can) then that motor is effectively disposable. That is a broad generality, but it's a pretty good guideline. Sure, you can replace bearings in any motor. I'm saying that in a cheap little rolled steel motor that by the time the bearings are shot so is the rest of it.

Now, speaking practically:

In all practical terms, so long as the motor is the right type for the application then it's just not something you need to ever worry about. For example: the most ubiquitous small horsepower motor is going to be type TEFC.

TE - totally enclosed
FC - fan cooled

Being totally enclosed means that the motor is pretty much drip proof and dust proof. Water falling on the motor won't hurt it, but it's not waterproof, so it cannot be submerged. In just about any conceivable application, this motor is going to be fine even left outdoors. Most of them have rolled steel frames and they will rust over time. Running them does dry them out and keeps rust at bay for a very long time.

You can take it a step further and get a motor that is made for "Wash Down" applications such as food processing where they stop the production line every eight hours (whatever...depends on what's being produced) and they wash the whole place down with foam and hot water sprayed from high pressure hoses. These motors can withstand all of that. They are very expensive.

In the big scheme of things, unless you are doing something in an extremely demanding atmosphere, your typical TEFC motor is going to take a licking and keep on ticking. You don't need to do anything. It can sit for long periods of time without running. It can sit in the sun. It can handle the rain. Cold won't matter.
 
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Thanks John.

I had a $500.00 meat grinder that sat in a foot of water for about 36 hours. I don't remember how long it sat afterward, maybe a week maybe longer, before I got home and could open it up. It had corrosion on the magnet/armature (? not the windings), which I tried to clean with WD-40. I got it to work sporadically but not consistent. This is sort of where my question comes from about the different motors/tools I'm acquiring. I have two 1/2 HP motors right now and I'm glad to hear about them being able to handle the different temps. My shop area is my back porch which is enclosed but not insulated so whatever's out there feels the outside temperatures. I can heat up the work area and I was concerned this and outside temperatures and humidity was going to kill them before I get some good use out of them. Thanks the good perspective on it.
Luke
 
i see why you are concerned.

a motor with brushes in it will not play nice with water. a brush type motor with an exposed commutator will corrode quickly.

if ever an option, choose a brushless motor. look for "A/C Induction motor" in the description. way more robust, no maintenance to speak of. 3-phase is even better from that standpoint because you eliminate capacitors and switches on rotors. But of course that means you need 3-phase or a vfd.


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I'll be in the market for a new motor at some point in the near future... definitely be looking for a TEFC A/C Induction when I get to building a grinder.

You sent me to Wikipedia for the definition of a "commutator." This is the part I meant to refer to on the meat grinder.

I'll keep 3PH in mind, too. I have a 3PH washer motor not enclosed. When I took the motor off I took all the wiring with it in an attempt to figure it out. Funny story was when I thought about plugging it in (with no changes) I realized I was standing in a puddle of melted snow. I put it on the shelf until I can learn about 3PH. Also I kind of wrote it off because I learned an unenclosed motor could ignite if particles get into it. Didn't think it was something I could use for grinding anyway.

Luke
 
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