VFD outdoors, low temps --- bad idea?

[KM]

We need to add braking on a motor, and Contractor has proposed VFDs. The make and model he proposes is Télémécanique Altivar 31C with an IP55 enclosure. I'm nervous because I've heard VFDs are very fussy about the ambient temperature they like.

The application is hoist motors, outside, on a dam (lots of ice in winter, constant wind, very cold down into the -20s Celsius at times). Contractor proposes putting them inside the existing electrical enclosure on the crane, which would at least get them out of the wind and spray although temperature would still be low. Note product datasheet says it's OK to -10oC but has no discussion of what happens below that. Enclosure is painted black and would get pretty warm in the summer (where we get up to the mid +30s Celsius with very high humidity). Product data says we'd be OK to +40oC and slightly "derated" above that, but I'm not sure what that means exactly.

Contractor swears he's installed these on other outdoor applications around here and they work fine. And for all I know he may be right. However, I just wanted to check with other folks who have VFDs outdoors in this sort of weather conditions. So, how are they holding up?

If VFDs in this environment really seems like a bad idea, what other options are there? Changing the motors to the kind with brakes, I suppose. Anything else?

 

[jraef]

VFDs in cold weather has traditionally been a bad idea. Electrolytic capacitors can freeze, and if they do, they explode when energized. But many small drives are now built without electrolytic caps, so I suppose maybe that's why they say -10C, however make sure it says -10 OPERATING temperature, not just the STORAGE temperature. Two different things.

I would also not take that at face value, I would ask Schneider directly and get it in writing. In my experience, they are notorious for telling you something verbally, then not acknowledging that when things go south later.

I took the liberty to look up an installation guide for the ATV31C, I found this:

IMPROPER DRIVE CONTROLLER OPERATION
• If the drive controller is de-energized for a prolonged period, the
performance of the electrolytic capacitors will be reduced.
• If the drive controller is stopped for a prolonged period, turn it on every
two years for at least 5 hours to restore the performance of the
capacitors, then check its operation.
• Do not connect the drive controller to the line voltage. Gradually
increase the voltage using an adjustable AC source.
Failure to follow these instructions can result in injury and
equipment damage.

But later on, it does say:

Minimum and maximum ambient air temperatures permissible during operation:
-10°C to +40°C

If you think there is a significant risk that someone will energize these drives when it is below -10C however, that would make it unsuitable.

Also, this drive does not appear to have an option for an encoder feedback, so as a general rule, I would not like it for a winch application. But on a dam, I have to imagine it's maybe a weir gate winch? That might be OK. But how much braking capability do you need?

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[ScottyUK]

"Operation at -10°C" is different from sitting idle at -10°C : make sure it is not relying on internal losses to keep it warm and that you can actually start it at -10°C, not just allow it to operate at -10°C after having started at a warmer temperature. Schneider's specs are sometimes very cute, I think lawyers must write them.

 

[ozmosis]

KM
It is a misconception that high IP rating means it is suitable for outdoor mounting. You cannot go off the numbers but have to design it accordingly.
In NEMA/UL land, enclosure classification clearly identifies for indoor and outdoor.
A NEMA 3R enclosure is a relatively 'low' IP level but is designed to ensure moisture ingress and dust ingress as well as protection against sunlight and condensation with heaters that switch on when there is a temperature delta (typically) >10C.

I strongly advise against mounting an IP55 outside unless you have direct sun protection and some control on condensation build-up.
A drive rated at 40C means the ambient airflow through the drive is max'd at this level. Put a drive in sunlight and the internal temperature will shoot up.
I suggest you consult with a good quality installer and design it accordingly or mount the IP55 inside another enclosure away from sunlight and other nasties.

 

[micalbrch]

Why not use an IP 21 VFD and get a suitable enclosure with air condition, moisture detector or whatever is necessary? Yes, that's more expensive than an IP 55 enclosure VFD but can avoid the temperature problems. And you can get rid of the black enclosure.

 

[ozmosis]

micalbrch
that is what most people do with a NEMA3R enclosure.

 

[KM]

Good considerations all---thanks. I will be asking him to propose some alternatives. This has all the markings of a can of worms waiting to be opened.