VFD at 55 Dec C Ambient

[sunrays]

I need to use a VFD on a crane application with the ambient around 55 Deg. C. I would be using a Panel Cooler, but in the eventuality of the failure of the Panel Cooler for any reason I need to continue to use the crane till the cooler is put back in circuit. The manual for the drive selected specifies a current de-rating factor for the drive up to 50 Deg. C only.

My question is it advisable to use this drive beyond 50 Deg. C? Should I select a higher rating of drive to compensate for the higher ambient? What is the maximum ambient that a VFD can be subjected to?

Thanks for your advice in advance.

 

[itsmoked]

The maximum is entirely up to the drive maker.

If you allow operation after the cooling system fails you might as well forget the cooling system, because it will fail, and the crane will continue to be used as long as the crane still runs, no one will fix the cooling.

Better would be to restrict the crane operation to some suitable speed reduction so the crane still works but operation is hindered until the cooling is returned to correct operation. This essentially protects the VFD and still allows some use of the crane, but demands repair of the cooling system.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dpc]

I agree with Keith, but also I think the answer depends on how much it costs the operation when the crane is out of service. You could just buy a spare drive.

One crane is generally not ever going to have a VFD loaded 100% all the time. There will be a duty cycle.

Oversizing the drive could help with the power electronics side, but the logic side could still overheat in a high ambient - depends on the design and layout of the VFD.

"The more the universe seems comprehensible, the more it also seems pointless." -- Steven Weinberg

 

[DickDV]

As far as I am aware, all VFD manufacturers use commercial grade integrated circuits for the control boards. Their temperature range is 0-40 degrees C. Even tho I work for a manufacturer that does offer a derate to 50 degrees C, you are really reaching on the electronics to do that. To go beyond that even with further derate is unlikely to be wise, in my opinion.

 

[ozmosis]

As with DickDV, I work for a VFD manufacturer who offer high temperature operation but with deration. We offer 50C as standard maximum and then you need to look very carefully at the load and rating of the VFD for applications >50C.
I get asked this a lot about high temperatures and invariably when this is posed "can I operate at >50C?" I express real concern because each 1 deg has a massive impact on electrolytics and most silicon based components, and I know that when you say or others say "55C" that you don't actually know it's going to be 55 maximum. All you know is that it will get bloody hot. This is not too accurate and yet companies expect some level of guarantee etc.
Our VFD will automatically derate when hot but if the ambient is very high and the VFD is not running, then damage will be done and the VFD cannot really protect itself.
These are aspects you should consider. My thoughts are that if you are looking at protection, do not allow the VFD to do this, especially in a crane application. VFD's protect against high ambient by a number of actions: lowering switching frequency, lowering output frequency, current limiting etc. I would say this is not what you would require in a crane application.
Finally, if designing for high ambient, you should really oversize the VFD to cope with the manfs recommended current rating. This is always based on a known temperature. If it is 55C then the rating will be based on 55C. However, can you guarantee 55C? I guess not.