The KBAC24D is not really suitable for a lathe operation.
Not disagreeing, but I wonder if you could say more. I had a KBAC-24D on a 2 x 72 belt grinder with a 1 HP motor, and ran it that way for a few years (hobbyist use, not full-time in a busy shop). Because if the wimpy motor, I did bog it down fairly frequently, and the protection circuitry on the VFD would kick in, so for all of my intents and purposes, it was fail-safe. Maybe I could have killed it eventually, but I'll never know, because I recently upgraded it to a 2 HP motor and a KBDA-27d. As well as being bigger in size and amps/HP, it's also the newer style with LED display, programmable from the front panel, which is handy. I have the display programmed to show the belt speed in SF/min., just because "why not?" The grinder is now purt nigh unstoppable.
The "washdown" NEMA4 enclosure is utterly immune to dust, grit, swarf as well as water if you want to leave it out in the rain... not that I recommend that.
Anyway, I'm not an expert. I have 5 VFDs now, all KB brand, so I haven't tried the other candidates, but I'm 100% satisfied with the performance, protection, and dust-proofness of the NEMA4 KBs.
My lathe, a 12" swing benchtop with a 1.5 HP motor, uses a KBDF-27d which is
not NEMA4, it's open to the air (NEMA1 or IP 20). I didn't build an enclosure for it either, I just mounted it up pretty high and away from any showers of swarf. Been using it that way for 3 years now, no zaps, no smoke. Oops, now I've jinxed it!
I only got the KBDF because it was super cheap on ebay as "open box", so I took a chance on it. So far so good, but if I could afford it, I would go for the KBAC or KBDA models, with the washdown enclosure.
The little KBAC-24D is limited to 1 HP, but OP said his motor is 3/4 horse, right? Do you think the 24D is undersized for that motor? If so is it because of inadequate braking? You can program it to a long deceleration time, which should minimize the threat to the braking resistor, no? Though I suppose someday in a crash you might wish you had faster decel. I'm pretty sure if the VFD attempts and fails to decel the machine in the alloted time, nothing breaks or fizzles, it just stops braking and lets the machine coast to a stop. Maybe not the best for human safety, but at least the VFD is not harmed.
A couple of my VFDs are KBMA-24d, a super cheap model — for a USA-made VFD anyway, still more $ than Chinese, if you buy one new-retail. They're very basic, without a lot of the fancier features, but they've been running my 3/4 HP buffer and my 1 HP drill press just fine. They are NEMA1, but still surprisingly closed-off to grit and swarf, no problems so far in a few years of use, and that's in in the 'dirty' part of my shop where I have grinders. I even got them both used off ebay, with an unknown amount of miles on 'em (and dirt cheap). Very happy with those, for getting the advantages of VFD on a couple of machines where I wouldn't have done it if I had to pay the price of a "real" one.
Not sure if the KBMA is made anymore. It sure looks like a throwback to an earlier era. I'd take it over Chinese any day though. I trust any VFD from KB. Not a stockholder, honest! Since I tend to buy things used, I'm not even a very good customer, KB doesn't get much money from me.
One advantage of sticking with one brand is familiarity (ease of programming), and to some extent, spare parts. As in you can cannibalize the less-essential machine to keep the more-essential one running while you order a replacement.
Speaking of ease of programming, I find the KB manuals to be written by a native English speaker, and pretty easy to follow. I assume the better brands like Hitachi, TECO etc are good too, but I don't know. I keep hearing horror stories about the documentation on the Chinese though. Maybe that's rumors? I have no first-hand experience with them. I just hear a lot of stories of them burning up.
