Boxford AUD/BUD single phase conversion

Evening....

Has anyone done this on this particular machine? I'm pretty sure that I understand the general requirements for achieving this but no doubt will ha e various questions regarding the utilisation of all of the existing switches and controls.

Intend to purchase a VFD and integrate this into the machine base cabinet with a potentiometer. Want to retain existing start/estop switch and reverse-stop-forward switch. What are the pitfalls?

Will probably wire so that there is a long flex cord and 240V three pin plug exiting the machine. Is there a way to wire this so that I can revert back to three phase using a switch (I understand that if the answer to this is yes, that there would need to be something funky going on to switch the wiring configuration over at the motor junction box).

Your comments gratefully received.

Don't worry about going back to 3 phase after using a VFD you'll never want to.

I'm not familiar with the boxford switches but if they are momentary you'll be able to use them with a 3-wire control setup, if they act directly on the contactors it's a lot less straightforward;. TBH you might be better off knocking up a simple pendant control. Few, rev and speed can be done with a 3-way switch and a potentiometer is no time at all.

Thanks Pete for your thoughts.

Point taken regards reverting back to 3 phase. I was just thinking that , should I decide to sell it, it may appeal to a wider audience if this was easily achievable. I dunno, probably overthinking it.

I've attached a pic of one of the machines. The start/estop is quite modern, the fwd/rvs switch looks like it's original kit. Both can be seen clearly in the pic.

Edit: No idea how the image upload tool works. Will post the pic when I've figured it out.

Moderator edit: rotated photos.

Edited By SillyOldDuffer on 09/05/2022 22:09:50

Not sure why the album rotated them, nor how I correct it. It seems a clunky tool (the photo album tool, not the lathe). Maybe it's just me? ​​​​​

The white box is a NVR starter you won't be able to use that but you most probably would be able to use the original drum switch to the left of it.

EDIT you could use the NVR as a power switch to supply the VFD but you wouldn't be able to use it as a start/stop and depending on what model VFD you get using the E-stop on the NVR might invoke motor braking or it might allow it to run down normally. Killing the power to a running VFD is not recommended.

Edited By Pete Rimmer on 09/05/2022 21:58:26

Nice machine, but messy blockwork !!

Indeed! It was like that when I bought it! 

Edited By Kingofthehill on 10/05/2022 09:55:04

Not you, it's caused by a mismatch between your camera and the forum software: how orientation is recorded in a digital photograph is surprisingly complicated.

Can be fixed in two ways:

• Orientation can be nailed down with a photo editor before uploading. Basically, a human setting 'this way up' in a photo overrides the other alternatives. When a photo is the right way up in the Album, it's good to post.
• A moderator can rotate photos in a post, but not in an Album. I spin wrong photos whenever I see them unless I'm busy - although a photo rotate only takes a few seconds, it can mess up the formatting of the rest of the post, which takes much more time to fix, if at all. I don't mind being asked to try a rotation by PM, but the other moderators aren't as well placed as me at the moment for extra work.

Dave

Check the motor can be wired Delta 240v.

The rating plate suggests that it can be. Suppose I won't know for sure until I pull it out of the cabinet and have a look.

If it turns out to be hard wired star, don't immediately reject the motor. I recently rewired such a motor by digging out the star point on the windings. It wasn't difficult to do.

Regarding all the existing switch gear, I would ditch the lot when fitting the VFD. A modern rotary or toggle switch is easy to wire up for controlling motor direction.

As regards keeping the machine 3-phase compatible - that is probably trivial. Most VFDs accept single-phase but have input connections for 3-phase input. Take out the single-phase mains lead, wire in the 3-phase cable, and you retain all the VFD, pendant, etc, capability.

3 phase input VFD would suggest a 380-415v AC supply so not suitable for a unit designed for 230v AC single phase supply.

Emgee

Thanks, I'll bear that in mind. Not sure what to replace the start/stop switch with though? I assume (having also noted Mr. Rimmer's comments above) this will need to be wired on the output side of the VFD unit and therefore compatible with the output voltage i.e. 3ph 230V?

Edited By Kingofthehill on 10/05/2022 19:52:19

Edited By Kingofthehill on 10/05/2022 19:55:58

sometimes photo orientation can just be a matter of being left handed especially if you are using an iPad or similar as most devices are made for right handers (they Arte the ones who ask you to do up an awkward nut for them)!!!

Not sure what to replace the start/stop switch with though? I assume this will need to be wired on the output side of the VFD unit and therefore compatible with the output voltage i.e. 3ph 230V?

Read the VFD documentation.

Usually there is an NVR on-off relay / contactor to supply power to the VFD & low voltage pushbuttons connected to the control inputs side of the VFD for motor direction and run / stop operation. Switching the VFD output is not usually recommended & could damge / destroy the VFD if the contacts are opened while the unit is under load.

That you are asking these questions suggests that you are not familiar with these devices - mains voltages can easily kill you so, if in any doubt, consult someone who is familar with their safe installation & operation. Don't guess or try "winging it" !

Nigel B.

I think the next steps for me are to get a list of parts together and maybe a wiring diagram, and pull the motor to check the configuration options.

Thanks to all that have generously contributed to this thread.

What size motor isit on your machine?

The motor is 0.75hp, roughly 0.5kW.