VFDs at low temperatures

[KNMurphy]

We're buying a new crane. Supplier has proposed VFD control for smooth operation, which makes sense. However, crane will be outdoors, unheated, over the winter (well below freezing). Therefore, I'm worried that electrolytic capacitors will freeze and be damaged. Supplier is brushing off this concern, but is not providing any technical details on proposed VFD either.

Are there VFDs available that don't have temperature-susceptible components?

Will we require something like the addition of a battery (and solar panel to charge it) to keep a small resistance heater going in the VFD enclosure?

 

[itsmoked]

Very possibly you will need some sort of heating.

I'd also tell your vendor, "If you don't tell us the specific model of VFD you propose to use we will not be working with you".

Keith Cress
kcress -

http://www.flaminsystems.com

 

[KuanYau]

To KNMurphy (Mechanical)
(OP)

1. One of the reputable VFD drive manufacturer states
a) stationary installation ambient temperature 0...40degC. Max. 50degC if Pn and I2 decreased to 90% ".
b) storage and transportation in the protective package -40...+70 degC "
c) Relative humidity <95% (non-condensing).

2. A small wattage panel heater installed at the bottom to maintain the enclosure internal temperature two degree C above the ambient is desirable; to ensure that no condensation happens. Add a thermostat installed at the top for maintaining the internal temperature and cut-off the heater when not required; or during operation when the self-generated heat is sufficient to prevent condensation.

 

[LionelHutz]

This crane is powered off and unused all winter?

The storage conditions for a VFD are without power applied and it complicates things to provide power to the panel for a heater with powering the VFD.

Both operating and storage conditions assume the VFD stays dry, which won't happen without some heat in the panel. Otherwise, you will get condensation in the enclosure during temperature swings. One way to lower the heating required and eliminate some of the effects when temperature swings occur is by using an insulated panel. Insulation also helps keep the sun from cooking the panel on a hot sunny day. The downside is that it can make it more difficult to get the heat generated by the VFD out of the panel.

 

[melspuds]

I have installed many drives that work cold conditions (-15F degrees or colder) and had no problems. I suggest installing a heater as KuanYau stated.
If the crane is a bridge or gantry crane, forget about using festoon and cable reel systems. I had many problems with both types of systems in the cold. Use a collector rail system. The covered rail type with open bottom is now the only way to go. To avoid any icing problem, I suggest a small cover, be put over the rails and the collectors, just above the rail hangers.
Good luck,
Dave

 

[jraef]

I have personally experienced a 40HP drive have the capacitors explode upon energization when frozen. They were in a Type 4x fiberglass enclosure and the force of the gas expulsion from the caps blew the door off of the box and sent it sailing like a frisbee into a ravine. I had warned the owner about installing a heater, but another supplier told him their drive would be fine. Besides, the machine (rock crusher) would not be run of it was that cold. He forgot to mention that to the operator...

For applications where power is turned off so a heater won't work, my plan is to use what's called a "freeze stat", a type of thermostat used in freezers that closes on temperature rise above freezing. Refrigeration supply houses have them on hand, it's the device used to turn on the compressor. I tie that to a line contactor ahead of the drive, then put the bulb in the air stream near the heat sinks. So if the temperature of the air is below 0C, the contactor is open and no power gets to the caps. When it rises above the hysteresis point of about 2C, the contactor closes and energizes the drive. I've used that for years and never lost a drive in freezing conditions. The other supplier pooh-poohed the idea and his drive exploded on site, right in front of me when I was there for commissioning the rest of the control system.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[melspuds]

jraef
I like that idea with a "freeze stat". I have always used cheap bimetal stat hanging on a sidewall of the panel. For crane use, you would need a manual override to unload the crane. A push and hold down button with a strong spring would get the load and operator to home.
I know that I am old fart, but I just can't get used to A.C. cranes. My whole career of 45+ years was if you wanted something heavy lifted and moved, you used D.C. Now with the drives A.C. is the only way to go.
Dave