Oak Controller & Rotary Phase Converter Questions

[Overtorque]

Hello,

I have recently aquired a Manford CV/SP500 knee mill, which I am intending to convert to CNC using an Oak controller. What makes this mill unique is that it is CNC-ready (ball screws, servo mounts, quill feed and VFD are already fitted, plus a pretty nice electrical enclosure), plus it came equipped with a 3 phase knee lift motor. Everything is wired for 3 phase.

Now, I have read Centroid's 3 phase tech bulletin, however I would really rather not have to rewire my mill as single phase. I plan on using an American Rotary series ADX phase converter, which is one of their higher end models. Voltage should remain consistent within 5% along all 3 phases, even under load.

So here are my questions;

1. Would it be acceptable to wire everything, including the Oak board, as 3 phase, using the above setup?

If the answer to question 1 is "no", then would it be acceptable to wire everything (VFD, lift motor, lube motor, servo drives, etc.) as 3 phase, EXCEPT for the Oak, which I will wire as 220v single phase using the 2 non-manufactured legs from the phase converter?

Thank you in advance for your help.

[cnckeith]

they Oak runs off of DC voltage.
most Phase converters are known to have a "wild leg" with widely varying voltages and phase, this wild leg will sometimes fry electronic power supplies and subsequently electronics connected to them..caused by the higher than normal voltages or way out of phase voltages.
in general if you have to use a phase converter you "isolate" the wild leg from any electronics, Oak, PC, switching DC power supplies, etc
Centroid warranty is void when using a phase converter, sorry we just have too many guys blowing stuff up with phase converters:-(
That being said, if you get a good one and wire it property it will work.,
but if you can do it running on single phase is MUCH better, VFD that accept single phase and output 3 phase are cheap and plentiful and more efficient than a phase converter. who wants to have a hot noisy phase converter box in there shop? the only way i'd go with a phase converter is if the machine has a large (over 10-15hp) spindle motor. for a knee mill running single phase and using a vfd is a slam dunk.
what servo motor are you using or plan on using on the knee mill?

[Gary Campbell]

+1 to controlling the 3 phase motor with single phase"

[Samandkimberly]

I didn't know using a phase converter voided Centroid warrantee. Guess I should have looked at the warrantee; I cant blame anyone but myself on that one.

I’ve got a bed mill with a 5hp spindle that I’m converting to an all-in-one now. It’s been running with a Milltronics Centurion 1 for some time with a rotary 3 phase converter; the controls are all wired to the 220 main and the wild leg goes only to the 3 phase VFD. With normally suggested debating I’d need to go with a 7.5 hp VFD, which are neither cheap nor plentiful. Do I really need to do that to keep in warrantee? Does it really make sense for me to mess with something that’s been driving other PC based controls with no problems?

In principle I 100% agree with single to 3 ph VFDs being the way to go, but it would be an expensive complication for me to change what I have when it seems to work well and have no bearing on anything but the spindle control.

Sam

[Overtorque]

they Oak runs off of DC voltage.
most Phase converters are known to have a "wild leg" with widely varying voltages and phase, this wild leg will sometimes fry electronic power supplies and subsequently electronics connected to them..caused by the higher than normal voltages or way out of phase voltages.
in general if you have to use a phase converter you "isolate" the wild leg from any electronics, Oak, PC, switching DC power supplies, etc
Centroid warranty is void when using a phase converter, sorry we just have too many guys blowing stuff up with phase converters:-(
That being said, if you get a good one and wire it property it will work.,
but if you can do it running on single phase is MUCH better, VFD that accept single phase and output 3 phase are cheap and plentiful and more efficient than a phase converter. who wants to have a hot noisy phase converter box in there shop? the only way i'd go with a phase converter is if the machine has a large (over 10-15hp) spindle motor. for a knee mill running single phase and using a vfd is a slam dunk.
what servo motor are you using or plan on using on the knee mill?

Hi Keith,

Sorry about the confusion, I know the Oak runs off of DC. I've been studying so many schematics, my brain is fried.

This mill is rather large for a knee mill. It's got a 5 HP spindle and weighs close to 4000lbs. I'm planning on using DMM's DYN4 drives with their largest servos (1.3kw or 1.8kw), since the servo mounts are designed for 130mm frame size.

So, if I go with single phase, I have a few questions (if you wouldn't mind).

1. How will I power the 3 phase knee lift motor?

2. In Centroid's TB163 (Rev1), there is mentioned an "inexpensive inverter" to use for coolant pumps, flood, etc. Could you please give me a part number for this inverter? Also, could this inverter be used to control the knee lift motor?

3. How long is the warranty for (Oak controller)?

4. If I go with single phase, could I reuse my circuit breakers, contactors, etc., and just remove the 3rd wire (assuming the amperage is still ok)?

Thank you in advance.

[Samandkimberly]

Maybe I should have done a little research before I posted; it seem there are rather a few no-name 7.5 hp 1 to 3 phase VFDs out there today for ~$250. I’d still rather not spend that for nothing, but it’s at least worth considering...anyone have thoughts on the low cost VFDs out there, or a specific recommendation?

[Gary Campbell]

I've had good results using a 5hp single phase rated V1000 from Yaskawa. Not bargain priced like you mentioned tho

[tblough]

Overtorque,

Inverter = VFD. The knee lift motor is probably a fractional HP motor and a VFD for that will be around $100. Do the same thing for your flood pump if you have one. Just wire it up and set it for 60Hz.

You can find 5Hp VFDs for your spindle rated for single phase input. If it's rated for single phase input, there is no need to upsize to the next larger size. Once you start checking, you'll find that the VFD route will be about the same price as the phase converter/motor starter/overload route, and you'll end up with the flexibility to adjust the knee speed and coolant flow if you wish.

[Overtorque]

Thanks for all of your replies. I've thought about everything and have done some more research, and I've decided to convert my mill to single phase using VFD's

It won't be cheap. A GS4 5HP single to three phase VFD is around $1,300, and a 1HP VFD for my knee lift is around $500. However, I did have $2k set aside for a phase converter, so I may come out ahead.

Thanks again.

[cncsnw]

Code: Select all

and a 1HP VFD for my knee lift is around $500

GS2-21P0