VFD for Mill

2nd UD. Hitachi is a bit better VFD. I think you should wire it on the low windings for better low end torque
 
I'd leave the HI/LO switch connected. Why limit yourself. Just don't switch it when the motor is running.

Greg
 
I have tried to use a hi/low configuration on VFDs using two speed motors, but my tries to wire the VFD to operate/use both speeds has been lack luster and often with disappointing results. This includes programming the VFD for both motor settings, which many VFDs include in their setup. My experience is to wire the motor for the low speed motor setting and directly wire this to the VFD. The motor connections should be clearly marked on the motor/connection cover. There are some exceptions, I have not dealt with 2 speed constant Hp motors in VFD conversions. You can comfortable over 1750 RPM speed (4P) motor to 1.5X it base speed of 60 Hz. Two pole motors (3450 RPM) usually are limited to 1.25X their base speed, I usually do not over speed them. You could push a 1750 RPM motor to 2X its base speed, but unless it is an inverter motor, there are some performance drop offs. Since high speeds are usually associated with smaller end mills/drills, you probably will never notice the difference and this is what I would recommend. Since the motor was already designed for this speed, cooling and bearings should not be an issue. You also gain motor performance by over speeding because of the ratio of motor speed to spindle speed. Torque wise, a 2P motor spins twice as fast but had 1/2 the torque of a 4 pole. When you add it all up with gearing/drive ratio to get the same spindle speed, I think it is a wash on torque. Still, in my experience you get better motor performance using a higher number of motor poles using a VFD. Granted this is empiric observation from a number of installation.

VFD wise recommendations, well it all depends on your budget and application. I would say 80% of the VFD builds/installs I have done have used the Hitachi WJ200, and it works well and has been reliable. Kind of middle of the road. Teco VFDs comes in many flavors and models, I would recommend a Teco (or most any other VFD) over an HY for numerous reasons. The HY may be more "economical" for especially for larger "single phase" input applications in the 3+ to 10Hp, but reviews and from other forums and VFD gurus really question both the build quality and the stated claims. It is the only VFD that I have heard of routine failures, so hit or miss, at a price point. Cheap it is works, Automation Direct has commendable VFDs, and their manuals and Tech support is great, but their VFD models are becoming dated, so like their popular GS2 model does not run sensorless vector control (I would go with the GS3), which provides significantly better motor control at lower speeds, and the GS2 is somewhat limited in the programming department. Still, on a mill it is more run forward, stop, run backward commands and a speed pot. Many people over think VFDs and the myriad of programmable parameters, when it comes down to it, in most hobbyist application there are only a few parameters to set to get your machine running. Many/most of the parameters are for much more complex applications. Yaskawa makes very nice drives, along with ABB, and a few other higher tier manufactures. In this application, I can't say that you would see any difference. Since I tend to design a bit more complex VFD systems with "more features" I use drives with more programming flexibility and inputs.

There are a number of posts regarding installation of a VFD on mills, wire the VFD directly to the motor, wire the VFD input to power via a disconnect preferable using a breaker or quick acting fusing. Use a remote pod for a speed pot, E-Stop, and run controls. The run commands/controls can be 2 wire control using a Forward Off Reverse switch just closing the input contact, or 3 wire control with momentary Stop, Run and motor direction. With 3 wire control that uses momentary controls, in most case will not auto start if power is applied vs. 2 wire. Most VFDs also provide a setting so the VFD will not run if powered up in a run commend mode. This does work, I have tried it on several VFDs. So some basic skills, but a VFD on a mill works very well in most applications, usually stepped pulley drives are preferable to the mechanical varispeeds.
 
I ended up ordering a Lenze AC Tech - ESV152N02YXB for this application along with a box with Start, Stop, FWD-REV switch and potentiometer. I know there are other and less expensive drives available and thought it was a good fit and all should be here in about a week. This will be wired from a separate 230, single phase rather than using the 3 phase RPC and if it works well, I'm might be ditching the RPC for entirely for VFD's. As far as the box with the Start, Stop, FWD-REV switch and potentiometer, what wire should I be using? A tech from the outfit that I purchased the drive from stated I should use a 9 or 10 conductor, 18 gauge, shielded wire, and I said OK. Started looking around on a few sites, not really finding what I was looking for unless I want to buy a whole roll, Not! I only need 8-10 feet. What are others doing. I'm probably getting wrapped around the axle on this one. lol Thanks in advance!
 
eBay is a great choice for short lengths of multi conductor. mcmaster carr also. 18 gauge is the perfect size. My opinion, no need for shielded here.
 
+1 on what Karl said.
i have scores of VFD's in the machinery i repair.
the manufacturers of the machinery do not use shielded wire for their installations
we do not work in areas that have interference, nor do our machines produce interference .
i think it is safe to run your equipment without shielded cables
 
I think it is safe to use unshielded wire for short runs, like in a mill, as others have mentioned. But I have seen/had issues with VFD electrical noise interference. There are posts in other machinist forums dealing with VFD electrical noise causing false signaling, but this is usually with much longer runs between the VFD/Motor/Controls (and sometimes poor wiring). Do not connect the motor cable to the VFD signal wires or speed pot cable. Often VFD electrical noise can be picked up by radio and TV, and I have had to add RFI/EMI filters to the VFD input and also shield the VFD/motor cable to reduce the interference. You can also see increase electrical noise in the speed pot if remotely located, so if more than a couple of feet I prefer to use 3 or 4 wire 20G shielded cable, and I also adjust the VFD speed setting filter. This is low level, but you can see it as jitter in the speed Hz displayed. Many VFD equipped commercial machines have electrical input filters, and the VFD wiring is often internal to a grounded enclosure. Wires may be separated as to control voltages/mains voltage and wires may be twisted to decrease electrical noise.

Electrical grounding is a strange one, and not always what you expect. In general try to bring all your earth grounds to one point in the VFD cabinet or main power input (Star Ground). There are different options if you do use shielded wire as to grounding one end (usually at the VFD end), both ends, or neither (floating). There are also different cable/shield configurations which may also affect the grounding. In one install, the tach meter went wild when the cable shield was grounded in a VFD system. It only worked if the cable shield was floated at both ends. Anyway, should not be an issue with short wiring runs. As far purchasing cabling in short runs, as others mentioned eBay is a decent source, there are some online vendors that sell shorter runs but the shipping can bite you.
 
All starting to come together, new breaker box installed, drive and controls arrived yesterday, and drive control wire/cable should be here by Friday. I picked up a Hoffman enclosure today. I'm stoked and pretty confused to be honest. A few things I could use your guidance with; a. connecting the motor, being a two speed I would like to use the low speed side as per previous recommendations, at the motor box, I have the six wires U1,V1,W1(black) and U2,V2,W2 (red), which ones do I use and what do I do with the other 3? I've read somewhere on the many forums they are tied together. b. Control box with individual buttons for Start, Stop, a switch for fwd/rev and a pot, would the start and stop buttons be considered a three wire between them both ( found that on Marshall Wolf, http://www.wolfautomation.com/media.../actech-smvect-nemafourx/actech-smvwiring.pdf. Any other guidance is greatly appreciated.motor box (2).JPGswitch box.JPG
 
I have Delta, Huan Yang, Hitachi, Mitsubishi, and one without a name on it. (Came on a machine). None have given me any troubles except when I overloaded them and tripped their internal overload protection. Press reset and I am good to go. I have heard a few (marginally few when you consider how many there are) more negative comments about Huan Yang than the others, but most problems seem to be spindles and setup which is not always easy for the neophyte.
 
I have heard that there are some Chinese Huan Yang counterfeits out there to watch out for on Ebay. I always buy from a long term Ebay seller with a lot of feedback and less than 0.5% negative. Then I review recent negatives to see if its bad product or just slow boat from China syndrome. Anybody selling significantly cheaper I just assume is questionable.
 
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