MV VFD Feeder Circuit Protection

[mbk2k3]

For a VFD such as a 4.16 kV Powerflex 7000, are feeder circuits normally protected by fuses or circuit breakers?

If fuses, which type of fuse from here is most fitting:

http://www.cooperindustries.com/content/public/en/bussmann/electrical/products/medium_voltage.html

I am leaning towards the R rated fuses:

http://www.cooperindustries.com/con...ets-b/Bus_Ele_DS_6001_JCK_JCK-A_JCL_JCL-A.pdf

I'm worrying from the point of view that switching in the VFDs may produce spikes/harmonics/etc.

The AllenBradley rep that I spoke to gave me a convoluted answer saying that either fuse or CB is fine, but focused on the fact that the Powerflex comes with internal protection tools that don't need to rely on protection from external devices.

 

[jraef]

Well, the PF7000 does not pose any particular added issues with regard to circuit protection of the feeder going to it, that's true. But the protection functions within the drive are for the drive itself and the motor circuit down stream, the drive cannot provide protection for upstream circuit components.

However, fuses or circuit breakers are fine, no special considerations are necessary. The manual suggests R fuses and if you were to purchase the drive with a "Line input starter" option, that's what you would get.


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

 

[mbk2k3]

yes sorry, i meant protecting the upstream feeder/cable that feeds the VFD. thats the one I'm wondering whether to use fuse or CB.

 

[ukgraduate]

You can use either.

It is simply a feeder to the VSD. The VSD may have some signals it requires to go back to the upstream feeder contactor or breaker for protection of the VSD itself.

 

[LionelHutz]

R rated fuses are not full-range fuses and should only be used with a relay. The relay protects against overload and the R fuse protects against shorts.