That's probably why I didn't think it was common. Since all I want or need is 60Hz that's all I've ever set one for.

You might find use for speeds higher than 60Hz. When I put a VFD on my lathe I decided to omit the mechanical gearing (belt change pulleys). It had a 1HP single phase motor which I replaced with a 2HP 3 phase motor, and I geared (belted) it for a permanent low-mid range. To achieve the higher speeds that it used to be capable of, I exceed 60Hz.

 

My lathe has a multi-speed gear head stock, and the Bridgeport is a variable speed so 60Hz works good. My 2 older lathes I retro fitted with DC variable speed motors.

 

That's probably why I didn't think it was common. Since all I want or need is 60Hz that's all I've ever set one for.

My reasoning when using a standard 4 pole motors with VFD, to usually go up to 120Hz, I figure the balancing and bearings used by the manuf will be the same as their 2 pole models, so the 4 pole will be safe to run at x2 the plate RPM.
Max.