Lathe motor upgrade DC to 3-PH + VFD  Finding suitable 3-PH motor - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: April 10, 2022, 04:53:11 pm
content: [ Specified attachment is not available ]I have converted both my drill press and milling machine to VFD in the past and want to do the same for my small 10x28 lathe. For the replacement 3-PH motor I'm trying to determine the equivalent or compatible IEC or NEMA mounting dimensions. Can anyone nudge me in the right direction?This is a made in China lathe and it appears to be originally made for Weiss and is sold under various brand names: Weiss (WBL250F) Precision Mathews (PM 1022V), and Craftex (CX706). I have the CX706 variety.The original motor has a Weiss sticker with the model # 108ZYT-005AL. Searching for a datasheet or drawing for the original motor has not yielded much, but I did find the following (see below) that appears to be similar, same shaft diameter 12mm my motor has a flat flange with the mounting tabs flat to the front edge (see red box). The motor is presently installed so measuring the center to center mounting dimensions is far from precise, my rough measurements for the short distance is ~ 88mm [3.47"], which agrees with the installation center distance in the chart below. Pythagoras yields 125mm [4.92"] for the longer distance and that is also what I measure.So to summarize looks like I need a C-Face motor with a bolt mounting spacing of 3.47" (125mm), I'm not sure there is a compatible NEMA or flange mount?The "C" flange B15 frame size 100L is 130mmThe "D" flange B5 frame size 71 is 130mmOne step down is 115mmShaft sizes are also different, need 12mm, IEC/NEMA shafts are 11mm, 14mm

author: geggi1
author_rank: Frequent Contributor
timestamp: April 10, 2022, 06:33:50 pm
content: From what I can se it is something not standard so you will probably have to make some adapter to make it fit.Look in this linkhttps://static.weg.net/medias/downloadcenter/ha0/h5f/WEG-motors-specification-of-electric-motors-50039409-brochure-english-web.pdfon page 51.Be aware that when using a VFD you might have to use some additional cooling for the motor because on low RPM you will not get sufficient cooling.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 10, 2022, 06:41:17 pm
content: I wouldn't consider moving from DC to 3-phase with VFD an upgrade for such a small lathe. Just get a decent DC controller. Some of the best manual lathes ever made (e.g., Monarch 10EE) used DC. It gives an instant on, soft start (if you want), and easily controlled speed. The 3-ph converters I have seen show a definite lag from "start" to actually starting. Basically, it is probably a toss up (if your lathe has half-nuts and a threading dial), but why throw away a DC motor, and instead of a cheap DC controller get a full 3-ph setup? If your lathe lacks half-nuts, then DC is the best way to go. My Prazi hobby lathe is like that.

author: Jester
author_rank: Frequent Contributor
timestamp: April 10, 2022, 07:07:43 pm
content: Quote from: geggi1 on April 10, 2022, 06:33:50 pmThanks for that, well it should be pretty easy to make an adapter to sandwich between the motor face and the mounting plate and then I can drill/tap 2 different diameters, one to match the original mounting plate and the other to match the new motor. There is some room to grow in all dimensions so perhaps a NEMA 71 or 80 will be a good fit. The shaft might be more of a challenge 12mm seems oddball

author: Jester
author_rank: Frequent Contributor
timestamp: April 10, 2022, 07:19:01 pm
content: Quote from: jpanhalt on April 10, 2022, 06:41:17 pmPerhaps a better dc control board might be worthwhile. One of the reasons I'm considering the VFD is because I'm thinking about adding CNC capability and need to be able to control speed and direction of the motor which is really simple with a VFD and not quite as simple trying to modify the original controller (no schematic) in an elegant way so I can flip back and forth between the original controls when operating manually and then letting the controller drive when doing CNC. Perhaps I should be looking at CNC friendly DC controllers?I have an electronic Lead Screw controller for threading.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 10, 2022, 07:24:42 pm
content: Controlling direction and speed with a DC motor is incredibly simple. It is almost instant reverse. I use a controller from KB Drives that cost less than $120 (new, ebay) for a fractional HP DC Baldor motor running off standard US 115V AC. Look up KB Drives.

author: Jester
author_rank: Frequent Contributor
timestamp: April 10, 2022, 11:17:31 pm
content: Quote from: jpanhalt on April 10, 2022, 07:24:42 pmOut of curiosity what KB drive are you using?I actually have a KB drive (I think it's a 120 or 125?) driving an old treadmill motor nowWhen reversing with your KB drive are you simply providing a logic signal to reverse or are you actually reversing the output drive to the motor with a DPDT relay?I picked up both of my VFD's on ebay for about $50 (one used and one new). I power them with 230V, to avoid loading up the 120V receptacles in the shop. I'm a VFD fanboy, I just like the way they work.