I don't mean to offend any one but there has been a lot of nonsense mentioned here with respect to the ABB ACS355
None taken Dick, however, I too have been around ABB VFDs for quite some time; the old ACS600s were and the newer ACS800-880s still are my top choice when needing to supply variable frequency to an application requiring extreme torque accuracy.
There are many valid reasons one would upsize and/or derate a VFD application and the manufacturers provide the user with the capabilty to do so when the need arises.
I have never had to use a higher rated ACS600/800/880 than the motor(s) to be driven HP; they've all performed as advertised and proved to be long lasting workhorses.
I did have issues with the ACS355 family though, not surprisingly when comparing the prices of the two VFD lines. The 355s are extremely cost effective for a reason; I always upsize 355s for multiple motor applications when not given the choice of using something else; this might sound as nonsense to some but establishing intended/specified functionality at minimum cost overruns is the name of the game afterall.
The 800-880s do not provide 'carrier' frequency amplitude user settings while the 355s do.
Why would ABB configure differently two lines of the same device type?
IMHO, because one VFD line might need said derating in order to satisfy the advertised functionality while the other one doesn't.
Like my Grandpa used to say: "Ya git whatcha pay fer!"...