converting Keiyo Seiki to run on single phase 220V help

Hello all, this is my first post on the site and I am looking for some help.

I just picked up a beautiful a 5hp Keiyo Seiki KM1800 17"x48" lathe that runs on 3 phase 600V and I would like to change it over to run on single phase 220v. I did this with my milling machine and it was just a matter of having the motor rewound.

With this lathe that I just picked up, I opened up the electrical panel and was shocked at all the stuff that was in it. I just don’t understand why it is so complex. Everything on the lathe is manual expect a switch for the foot brake and forward and reverse, and outlet for the coolant pump. I wrote down some of my thoughts.

Would anyone help me to look it over? I was also looking at get some replacement equipment if needed. For example the allen Bradley overload and the forward and Reverse as I don’t know if they will be able to handle the extra amperage of using single phase from 3 phase of even if I can use them with single phase reversing motor. From the picture if you zoom in, the overload 140-mn-1000 looks like its rated for 30amps… but at 600v.

Thanks again

Sorry I am not sure how to turn the photos when attaching them

I've done similar conversion with a Colchester 21" lathe with a 15 hp 440v motor.
In my case the motor has several wires into the windings. Depending on the manufacturer these motors can be configured either 440v or 220v depending how these wire are connected.
Remove the motor cover, or maybe check the motor plate to see what options you have.
So I reconnected the motor for 220 volts.
I then got a VFD (in my case a Fuji). I wired the VFD directly to the motor contact strip, completely bypassing any existing control gear in the panel. This is important as you don't want any switches or breakers, or overload devices between the VFD and motor, otherwise you can toast your VFD !
In my case I was able to locate a switch on the headstock to control the VFD, to turn it on/off and therefore the motor on/off. There is virtually no current or voltage in this circuit as it simple "makes" the switch contact on the VFD.
In my case there is a mechanical clutch between motor and spindle. If there is no clutch, then the low voltage switch about will start/stop the spindle directly.
All the overload and breaker functions are controlled by the VFD directly. There is of course a need for a breaker to isolate the whole VFD.

If your motor cannot be changed to 220 volts, then you can probably find a used 220v 3ph motor quite cheaply. You could of course go to a single phase motor, but I have no experience.
I have converted several 3ph machines to 220v single phase in this manner. It works really well ! VFD's can give you other benefits as well.

Please do not hesitate to contact me if I can help you further.
Bob

Thanks for the information.. My motor doesn't have the 220v three phase options and there is no nameplate on the motor to even see what frame size or rpm, etc, it is. Thats why I figured it would be perfect to just have it rewound, cause the place ding the work could rebuild it and tell me all the information.

I just don't understand why it's so complicated in the box. Don't I just need a soft start, forward and reverse switch? That's all my milling machine has. The VFD options is a good option but having the motor rewound should be easier. I just have to figure out what stuff to keep and what stuff to get rid of in the control panel. Anyone have any thoughts?

I don't know but I imagine rewiring a motor like that would not be a simple task, and therefore $$$$$
A top class Fuji VFD would be about US$500, plus the cost of the replacement motor.
Good luck,
Bob
10hp vfd | 10 horsepower variable frequency drive

to get the motor rewound is about $500CAN or $350US at a place here in Mississauga Ontario. Then I know i have something that fits and is the correct RPM size etc. Just need to figure out all the rest of the controls in this box.

You could make your own 3 phase with an RPC and boost it to 600 volts. Then, you'd not have to mess up that nice looking set-up in the electric box. Do it the easy way and save a lot of F**king around.

I looked at the rotary phase converter options, but they recommend a 3:1 ratio for horse power rating. So since my motor is 5hp, I would need a 15hp rotary phase converter and that would be $2500CAN, or about $1800US.

I just don't understand why this is so complex. My milling machine just has a forward and reverse switch.. that's pretty much it. The motor was rewound from the factory to run on single phase 220v. Wouldn't this be the same? and I could eliminate most of that control box? I know the control box is handy in a industrial shop in that all the controls are in the box and you just have to plug it in to any source... but mine is not getting moved once installed. Coolant and digital readout can be on a separate plug. The only think I would think I should need would be the forward and reverse switch and figure out tying in the brake switch.

I know the transformer in the control box can be eliminated as I won't need it to jump down to 120v for the coolant pump and DRO. Can I not just use a forward reverse switch like my milling machine? I don't think I need the overload as I am hooking it up to a breaker in the panel. Since the milling machine is from 1970 the motor probably needs a good rebuild anyways, and that would be included in the rewind. I don't mind learning a bit about this as well. I have time now to figure stuff out, so I would like to try and figure out a more economical way to do it.

If the motor is a standard frame buying a new 5hp single phase is a possibility. Perhaps a pic of the motor would be useful

Unless you are full load starting on a phase converter you do not need anything that large.

The motor isn't really standard. It looks like it was a 213T with a metric 112M base on it. The shaft is longer than a standard 213T. The motor shop I have been talking to said it was probably made for that lathe as the length of the shaft is over 4" for the 4 belt pulley on it.

I can convert the motor to single phase no problem. that isn't the issues and it's pretty cheap to do so. I am just curious about getting the rest sorted out for the controls.

Anyone else have any input on this by chance?

b4runner said:

Anyone else have any input on this by chance?

Click to expand...

Your control box is pretty slick and not that complex at all. And you want to do a single phase conversion to all that.

All your controls are 120V. If you built a 7.5-10hp RPC than you would change out that control transformer or maybe strap it differently.
You already knew that a 600V motor wasn't going to work for you so that is going to be an expense. A 5Hp 230V 3phase motor is not that much.

1. Let's see that transformer name plate.

2. Is the motor a dual voltage? You mentioned that the plate is gone. So how many wires come out of the motor wiring box?

b4runner said:

I looked at the rotary phase converter options, but they recommend a 3:1 ratio for horse power rating. So since my motor is 5hp, I would need a 15hp rotary phase converter and that would be $2500CAN, or about $1800US.

Click to expand...

A 10Hp RPC is the thing to do, not go to 15Hp.
A used 10Hp idler and a way to provide power to it. (Contactor, switch)

The motor is not dual voltage. I don't have a picture of how many wires come out of the motor wiring box, but can get one... but I know it's not a dual voltage unit. See attached for the transformer name plate. For the transformer, would I need it if I am using a 220v single phase input? As I would just use one leg of the 120V for that and the common. In the original post I have the schematic adjustment that I would think would work.

I would just like to see what I could use of the existing set up. As I mentioned with my milling machine it originally had a 3phase motor that was rewound to run on 220v single phase and all there is, is a eaton motor start box and a forward reverse switch, and it was very simple. Originally I had planned on using a VFD but found out it was already converted years ago.

When I original bought the lathe I figured it was gonna be just a matter of rewinding the motor to single phase and that was it, pretty much. It has been done for years.

So it seems everyones opinion is the keep everything as it is, but have the motor rewound to 230v 3phase.. since I can't find a replacement for this as I don't know the rpm, frame size, etc etc..( also the motor is from 1970 and a rebuild isn't a bad idea) and buy a rotary phase converter or VFD? So what is the benefit of that over a single phase operation other than single phase uses higher current for the same 5hp operation?

b4runner said:

For the transformer, would I need it if I am using a 220v single phase input? As I would just use one leg of the 120V for that and the common. In the original post I have the schematic adjustment that I would think would work.

Click to expand...

That transformer is not useful, some of those Hammond transformers have more taps. My house wiring is 220V in and all 120V circuits are on one leg or the other.

b4runner said:

So it seems everyones opinion is the keep everything as it is, but have the motor rewound to 230v 3phase.. since I can't find a replacement for this as I don't know the rpm, frame size, etc etc..( also the motor is from 1970 and a rebuild isn't a bad idea) and buy a rotary phase converter or VFD? So what is the benefit of that over a single phase operation other than single phase uses higher current for the same 5hp operation?

Click to expand...

A RPC is the easiest. Build it from scratch.

A VFD will have to connect directly to your motor.

Ya the transformer on there is for the coolant pump and DRO so you can just plug everything into the lathe and move it around. That's not a big deal to me.

I have attached a picture of the motor wiring coming out of the motor.

So in order to use the RPC, I was still need to have the motor rewound to 240v 3phase from 575 3 phase correct?

as asked earlier, So what is the benefit of a 3phase with a RFC over a single phase operation other than single phase uses higher current for the same 5hp operation?

The picture isn't the greatest, but there are 4 wires, 3 phases and then ground.

I learned from this forum that a 3 phase operation will appear to run smoother than a singled phase motor.
In the sense of vibration and small variations that could make a cut look worse than it should.

b4runner said:

The picture isn't the greatest, but there are 4 wires, 3 phases and then ground.

Click to expand...

The motor could be replace by a used one. Get a used one, install new bearings and paint the case. I've done this before.
Otherwise if the motor is a special case then a rewind. There are articles on this forum that describe this. Also on you-tube.

it runs smoother? So less vibrations? Are the motors balanced when they are built or rebuilt? So the surface finish will look a bit worse. Hmmmm, that seems like its more theoretical given a 3 phase motor is better balanced, but I don;t know if that would show up in the working piece, or was there a post somewhere on a comparison?

Well. you appear to know all the variables. I would add that the bastardization of a machine can be a one-way or two-way process.
I would not alter a machine like this, but my observation is:

A one-way ticket is a alteration that cannot be undone. You or your kin have to live with it.
I can think of a situation in the future where your altered machine is auctioned off and the new owner would say "Jez, why did they abolish Eugenics?"

A two-way ticket is a change that allows a 100% restoration if for some reason the alteration does not live up to expectations.

A no-change ticket. For me I got enough thoughts on how finished work should look or be designed. I don't need more complications.

And to add:
You should be versed in the RPC and VFD worlds. One is always a backup for the other.