RF 30 clone with bad motor now what

[markba633csi]

I don't mind changing belts on my Rotex- other than needing a step stool; gives me a little exercise
I use the mill only occasionally

 

[bulgie]

Any suggestions as to type/brand of vfd. I hate doing electrical, I get by but it is my weakest area of knowledge.

Most important for you then is one with an easy-to-read user manual. Written by a native English speaker.

Partly because of my "buy American" preference, I've only used VFDs from KB. Definitely more expensive than the bottom-feeders on whatever that Chinese version of Amazon is called, or on Amazon for that matter, but they use high-quality components and are super reliable. I have puchased all of mine (up to 5 now) used or "open box" on ebay, and all 5 have been perfect, but YMMV. It took some patience, with a saved search for the models I'm interested in, waiting for a good deal to come along. Maybe not possible for you if you have a deadline for getting this done. If installing a used one, do the "factory reset" (it's easy) to undo whatever settings they may have monkeyed with.

One advantage of KB is they seem to be popular with Youtubers — I've found multiple videos on how to install and program them. You'll still want the manual, but the videos were super helpful. For one thing, they focus on the few parameters that you need to set, and more or less ignore the dozens of other parameters that you can usually ignore. For the most part, entering a few numbers that you read off the motor nameplate is all you need, the other parameters have well-chosen default values.

It's often said that you should buy a larger-capacity VFD than your motor size, for example using a 3 HP VFD on a 2 HP motor. Probably true with the Chinese cheapos, but all of mine are running motors at or close to their stated capacity.

For my two machines with 2 HP motors, I went with the KBDA-27D. I also have used the KBAC-27D, which has analog controls instead of digital, no LED readout. You configure it with jumpers and trim-pots inside. Most people will prefer the digital interface on the KBDA, all settings controlled without opening the case.

Speaking of the case, both those models are fully-enclosed in a "wash down" enclosure, no way for swarf, grinding grit etc to get inside. The industry terms for this are NEMA 4X or IP65, Look for that on any VFD you're considering. The ones that have vents in the sides for a fan to pull air through, they need to be put in an enclosure that you design and build yourself, vented and with air filters over the vents, non-trivial to make. So a NEMA 4x enclosure is worth the cost to me for sure.

On the subject of motors, I have also gotten all of them used on ebay and every one has been perfect. There's just not that much that can go wrong on a 3-ph motor. Technically you want one that's inverter rated, meaning it was designed with VFDs in mind, but from what I've heard, most any 3ph motor from the last 40 years or so will work whether they call it inverter or not.

Lots of VFDs have the ability to run on 110 V 1-phase from the wall, and output 220 V 3-ph, but if at all possible, feed them with 220V. For one thing, most VFDs are de-rated (max horsepower is reduced) if running on 110V. Also the amps are double for 110V, so you need that much heavier copper in your wires and a bigger breaker.

I like American-made SJOOW (not a brand, that's an industry-standard term). It is very tough and durable. The first O means outdoors (why not?) "OW" is for oil and water-proof, and the J is "Junior", it means thinner insulation, for up to 300 V versus 600 V for SOOW. The problem with the thicker insulation was it wouldn't fit through the gland nuts that seal the entrance into the enclosure. The glands appear to be made for the J version. Chinese-made wire is probably fine if you're on a budget

Remember to get 3-conductor for wall-to-VFD, 4-conductor for VFD-to-motor. The motor cable can typically have thinner conductors than the one from the wall, for example I used 14-4 for the motor and 12-3 to the wall (on 220V of course). You know gauge # goes down as the size goes up, right? Gauge you need goes up if it's a long run, but most shops don't have a long enough run to where that factors in. Charts showing what gauge to use for a given current (amps) and length are all over the internet.

Caveat: I'm not an expert at any of this, one step above beginner, just sharing what worked for me.

 

[SouthernChap]

I don't mind changing belts on my Rotex- other than needing a step stool; gives me a little exercise
I use the mill only occasionally

Exercise? Well, I'm aware it's good for you!

 

[bfi]

Wow thanks bulgie for some really good details to get started. I can be impatient but no I don’t have to be in a hurry to get this operational, I’d rather look for those deals! I do have 220 in the shop for other equipment. I understand about the wire size and length of run. Turns out my neighbor is a retired maintenance electrician so I can lean on him. I’ll get some photos. Thanks to all again. Bart