Retrofit VFD, 3 Phase and a grounding question

[Mike Heaney]

Folks,

While turning holiday ornaments last week, my trusty, 70 year old Delta 1460 decided to give up on me- specifically, the motor bearing seized up. This provided just the incentive I needed to move into the world of variable speeds, reverse switches etc. I'm going to repair the old motor too, just to have as a backup.

I have purchased, and just received the following:
Y364 Inverter-duty AC motor, Marathon Electric MicroMAX series, 230/460 VAC, 3-phase, 1.0 hp, 1800 RPM, 56C frame
and
GS2-11PO AC micro drive, 1.0 hp, 115V, single-phase input, three-phase output, V/F (volts per hertz) control mode.
From Automation Direct.

Despite the pretty decent instructions that come with the controller, I do have a question, that I'm hoping you all may be able to help me with- it concerns appropriate approaches toward grounding things.

My plan is to mount the controller on a wooden panel, attached to the steel legs of the lathe. The motor will be mounted to the wooden lower shelf below the lathe.
My 110v power supply in my garage/shop comes with a conventional 3 wire setup. Therefore:
L1 and L2 and Ground connections come into the Controller (exactly as shown in the manual). These wires will be fed via a Kreg on/off switch (only to be used in emergency, or when the controller is in the "off" mode)- fyi, the full manual is available on the Automation Direct site if anyone wants to look it up!

I will connect the motor via the T1,T2 and T3 connections, and make the appropriate cross connections per the wiring directions on the motor plate.

The motor does not have a dedicated ground wire, so I planned to clean off the powder coat/paint around either the base mounting or one of the other screws on the motor housing and attach a ground wire from there and connect that back to the Ground lug on the underside of the Controller.

And that is where I just wanted to check something. It is not clear if this Ground lug on the controller connects back to the ground wire from the input supply, there is a suggestion that this lug is partly to ground the controller chassis itself, and somehow do that independently from the Ground that comes with the input supply). The instructions for the controller suggest that a wire from this lug should be connected to a screw on the enclosure, and that this should in turn lead to Ground- however, I do not plan to use an enclosure at this point. Some of the pictures show this ground as separate from the ground connection on the input side. Other diagrams in the manual suggest that the Ground lug on the underside of the controller does connect back to the ground on the input side. I do not currently have the facility to have a standalone grounding system set up, so ideally I am hoping that my plan of running a ground from the motor case back to the Ground lug will be sufficient.

Also, since neither motor nor controller will actually be mounted to the metal of the lathe, I had not planned adding a grounding wire from lathe/lathe legs to this- but I obviously could quite easily if this is a good idea. My thought was to have a ground wire from the lathe attached to the same spot on the motor housing as mentioned above.

Sorry that was all a bit longwinded! I hope it made sense. So in summary-
Ground in via normal house power supply- check
Ground wire from motor housing to Ground lug on Controller
Optional Ground wire from lathe frame to motor housing

am I safe?

many thanks

Mike

[Richard Allen]

Do not att an additional ground to the motor.

The wires provided from the controller are the only wires which should be connected to the motor.

Attaching a separate ground to the motor will cause ground loops. This would ay best result in the system not working the way you want. At worst the motor and controller will be damaged beyond repair.

[Mike Heaney]

Richard,

Thanks for your reply. With that in mind, do you have any idea why some of the controller wiring diagrams in the manual show four connections between controller and motor: T1, T2, T3 and a ground?

Thanks

Mike

[Richard Allen]

By all means use the ground wire from the controller. Just don't work a ground from some other source into the wiring. You should check the motor for a grounding point. You just want to eliminate a shock potential. You want to be sure that the only ground the motor can find is from the controller.

[Thomas Hotchkin]

Mike
I am new to the turning form, Have just got back into it this year. I see that you purchased a three phase 230/ 460 volt motor. Will your GS2-11PO AC micro drive, 1.0 hp, 115V, single-phase input, make up the 115 volts per leg that your motor needs? I have worked on a lot of 3 phase motors and know that they do not like low voltage, but will operate on some lower or higher freq. I just replaced the VFD on my lathe and had to reprogram it. Although its not the same brand it was not capable of increasing the voltage above input levels. Is it possible to set up 220 volt outlet at your lathe? You may find that you also need a braking resistor for your VFD if you turn large items, removes braking load from the small resistors in the VFD. Tom

[Steve Harder]

To answer your question about 115V -- that specific VFD will take 115V single phase and convert it into the 230V 3phase that the motor needs - because the motor is only 1HP. VFD rated for larger motors than that, from that manufacturer, require 220V single phase which is converted to 220V 3phase.

As to the grounding connection, usually you will find a screw with washer inside the wiring hookup box on the motor that is for the ground - that ground should be attached in some fashion to the ground of the 115V incoming feed. The ground lug at the bottom of the VFD is connected to chassis of VFD as is the ground connection at the top of the VFD that connects to the incoming line ground.

I have one of the GS VFDs and am very happy with it.

I do have a suggestion regarding placement of VFD - originally I had mine mounted on top of lathe motor - in a partial enclosure - but wood chips could get into cooling fan of VFD (noticed I wasn't hearing fan noise when VFD started.) So moved VFD to an overhead wood enclosure large enough to provide some cooling - I could do this as I had already built remote for VFD - here's a link to my article on building remote and my article on converting Nova 1624 to VFD.

http://www.woodturnersresource.com/extras/projects/1624remote/index.html
http://www.woodturnersresource.com/extras/projects/1624_vs/index.html

[Mike Heaney]

Steve and Thomas,

Thanks for your comments. As Steve mentioned, this controller converts 115v into 230v 3 phase. Steve- thanks for confirming what I hoped was the case- re the connections between the various ground lugs. Upon further peering into the motor wiring box, I did find a nice little green screw- to which my ground wire is now connected- thanks for the guidance Steve!

I've just wired it all up (after 3 runs to the hardware store to get the right gauge wires, connectors, metal cable casing etc etc etc. I have also just made a new shelf on which the motor will be mounted, plus a new shelf for the lathe to attach to on top of stand. While I'm waiting for the varnish to dry, I bench tested the motor and controller- things seem pretty good, albeit with a need for some fine tuning. I'm getting a little noise from the motor at low to mid speed, so need to fine tune the settings on the controller. Oh, and it is going backwards, so I need to swap a couple of wires around.

I have the remote cable for this VFD, so I have the advantage that I can mount the controller a little out of the way (probably on the right hand side of the lathe stand). I'm still trying to work out where to mount the controller remote, plus my emergency stop button. Up high sounds good, and I am wondering about mounting it on the right of the lathe rather than next to the headstock- taking a break to check out some lathe pictures online for inspiration! Steve- thanks for posting both your links, they were/are very helpful- especially since you dealt with a setup very similar to mine.

fyi- I do have single phase 230v in my shop, and I thought about going down the 1PH230v in; 3PH230v out route here, but decided to stick with my 115v in this instance as the motor power is relatively low, and I appreciated the added flexibility of easily moving the lathe location in the shop and still having a short lead to the power supply. I only have one 230v outlet in the shop, so that would have been more limiting.

Anyone with ideas for where to position your lathe controls- please chime in, I am open to suggestions!

thanks again

Mike

[Steve Harder]

Mount the VFD controller on something with rare earth magnets, then you can slide it around as you need to.

Just keep those wood chips out of the VFD enclosure, they sure like to find their way into the cooling fan.

As to the motor being "noisy" - check what P2.08 is set at. My motor (set at 12khz) doesn't "whine" at any speed setting - I have a 2hp setup. Don't run your motor at less than 12hz - I set my VFD minimum freq to that (P2.06). Have fun tweaking the accel decel time (P1.01 & P1.02)) to make your lathe nice and responsive.

[Mike Heaney]

Jan 2 update- things slowed down a little to allow for extra coats of varnish on the wooden parts and a few coats of red paint for the lathe stand- it all looks perfectly spiffy now!

I just finished installing everything, sorting out cable routes and tightening everything down. It all seems to be working well- speeds up, slows down, goes forward, goes backwards- what else could I possibly want in a lathe!

Steve- I am also set at 12kHz for 2.08- the manual suggests I can go between 1 and 15, although the controller only has options between 1 and 12- not quite sure what is going on there. I have tried all 12 settings and the highest seems best, but definitely some noise kicking in when the motor reaches 20Hz. The noise/wine is non existent below that frequency, and pretty constant at 20 and above- any ideas?

thanks again for all the help

regards

Mike