Bridgeport Mill 3 Phase - How to power?

Hello i hope someone can help.

I am new to this site and hope to become more knowledgable and able to contribute.

I am relativly new to model engineering and have recently acquired a Bridgeport Mill 1j head, from the serial it appears to be made around 1968. (I maybe wrong though)

My initial question is how to power it from a domestic single phase 240v supply in my garage.

The main motor is 3 phase, made by the English electric company and rated at 1 hp.

From reading various websites/articles I think I will have to power the motor with a VFD of some sort. But 440v or 240v?

I have taken the motor off the mill and it appears to be dual voltage. i.e. it states 220v / 440v on the stamped plate.

What I dont know is how to wire it (if possible) to accept a VFD 3 phase 240v?

Is it by re-wiring the drum switch?

I have read about STAR and Delta mode but this is where I cannot work out what to do with this motor, if indeed these modes apply to this kind of motor.

Any help in the right direction would be appreciated.

(I had hoped to include some images to illustrate my questions of the motor, drum switch and mill from my album, but cannot work out how yet.)

Rob

Rob, to get your pics from the album on to here, look at the top line of the reply box, second from the right end is a black camera, click on that and your album will appear.

Someone will appear soon to answer your questions.

Ian S C

Hi Rob,
To see if it is easy to change the motor from 440 volts (Star configuration) to 240 volts (Delta configuration) we would need to see a picture of the connection box on the motor. I would expect to see 6 terminals (Plus an earth terminal.) in the connection box. If it is configured for 440 volts I would expect to see three of these terminals linked together and the three others going to the reversing swtch. To insert a picture from your album click on the camera button on the top line of buttons above the box where you type the text of your message. You then select the picture from your photo album. The drum switch WILL NOT be connected between the motor and inverter but it could be used to switch the control signals to the inverter (Probably 12 or 24 volts) to reverse the motor.

Les.

Rob are you anywhere near Reading Berkshire? If you are your welcome to come to talk with me re the BP wiring and control. Or PM me for my phone number. I've had to do the same thing. John

.

Rob,

There is a helpful thread about how to post pictures; cunningly concealed here.

MichaelG.

Edited By Michael Gilligan on 04/03/2015 09:06:44

Hi Rob, The cheapest way will be to use a 240 Volt VFD and rewire the motor to delta. You do have the right sort of motor to be able to change it. The change has to be made on the motor itself. Where the cable goes in, there is usually a small plate held on by a couple of screws. Take it off and you will find a number of terminals, linked with small links with two holes in them so they just fit over the terminals. Now, with luck there will be a diagram on the back of the cover or inside showing how the links should be connected for star and delta mode. It will be in star mode as it came, and this will link the three coils to one common point. In delta mode the three coils will be linked in a triangle. You may find that one of the existing connections is made with two links, one on top of the other. This is because star mode only needs two connections while delta needs three.

In the existing star mode, there will be three incoming power connections, each connected to one end of a winding. The other end of all the windings connects together to the neutral connection. There should also be an earth connection to the frame of the motor. When it is connected in star mode, then the end of each winding will be connected to another winding, and they both connect to an incoming phase. Because they are now connected in a triangle, there will no longer be a neutral point, and you will find that the VFD device does not provide neutral on the output side. This is fine. The earth should still be connected as normal.

The VFD should connect directly to the motor, eg not through any existing switchgear, as it is not usually recommended to switch the output of the VFD. An isolating switch ahead of the VFD is still a good idea, although if it is going to plug into a wall outlet then simply turning off at the wall and unplugging will be a good way to isolate it when you need to.

If you find that the motor does not have the strapping diagram inside the cover, it might pay to get someone who knows about such things to look at the strappings for you.Or else take a photo and put it up here. You do want to get this right for several important reasons, like not cooking the motor, the VFD, or yourself...not necessarily in order of importance!

This is a really good conversion to do, since not only do you get the full performance of the motor, you get a variable speed, and the maximum speed can be higher than the motor would normally have provided. Generally motors can be run up to twice their rated speed without problems, although you might want to check what the spindle is rated for too.

John

Rob: The usual advice is to have no switchgear between the VFD and motor. The combination will run fine with intermediate switchgear, but, if you accidently operate said switchgear while the VFD/motor is running then you are likely to say bye-bye to the VFD. On Bridgeports use of the backgear reverses the spindle direction. The drum switch shown reverses the motor direction, by swapping two phases, when in backgear. It might be prudent to bypass this switch and use the VFD function to reverse the motor.

Andrew

this link shows and describes your options **LINK**

Rob, I have a 3ph Bridgeport, with power feed and a coolant pump. I run mine from a Transwave 1ph to 3ph converter. Once the main motor is running, I can then use the other 2 motors. All the solutions proposed above only deal with the main motor, so if you think you will need feed or coolant, both essential in my view to get the best from the machine, then you need solutions for these too. I did not touch any part of the electrics apart from put a 3ph plug on the end of the mains cable to fit the converter. I should add that I already had the converter to run my Bantam lathe, so for me this was a cheap solution, and did not involve me in messing about inside motors, something I personally am not happy about.

Chris Gunn

My advice would be would be stick with Chris’s plan. I have a 3hp, 3ph Bridgeport with a table power feed, coolant pump and a slotting head on the back. Stick a 3ph converter on it, preferably a rotary one and the machine works seamlessly.

Hi thanks for all the replies, a wealth of info already.

I havemanaged to access the album I created with photos to make things easier to know what I have

1. The first photo is mill
2. The second is the motor with drum switch connected
3. The third is motor with switch disconnected showing the 3 wires coming out - no terminal box?
4. The fourth is the best shot I could get of the rating plate on side of motor showing what I understand is its dual voltage capability.

Hopefully I could be advised on what is best way to go with powering etc.

Many thanks again for peoples time and advice

Rob

I would be inclined towards a dual stage inverter with a 415v 3 phase output as the machine has a auto feed on the x axis, do not know if it also has a coolant pump but if it has then with this option they will all work rather than just the main motor if you opt for 220v 3 phase. There is a cost implication but off set by not having to mess about with the auto feed. You will really miss auto feed, I can not think what I would do without it on my mill as I use it 99% of the time.

This is the route another person on here took with a dual speed Colchester lathe.

Bob

Edited By Bob Brown 1 on 04/03/2015 21:49:48

Good point about the coolant and fine feed...but are these actually three phase motors? Some machines have single phase motors for auxiliaries...not having a Bridgeport I don't know about these.

John

The coolant pump on my Bridgeport is three phase, as they are on all my other industrial machines. The table feed is a brushed DC motor, the controller running from 110V derived from a transformer across two phases.

Andrew

Hi Rob,
From the pictures of your motor it looks like there are only 3 wires comming out of it so it may have been rewound at sometime. If this is the case it makes configuring it for 230 volts more difficult. You would have to dismantle the motor and find the ends of the 3 windings to allow it to be connected in delta. I have seen reports of people running the coolant pump from single phase by using a suitable value capacitor to provide phase shift. I have not tried this myself. For the feed motor 110 volts supply you should be able to find a suitable 230 to 110 volt transformer. (There might even be a 230 volt tap on the primary of the existing transformer.)

Les.

I will be going same route shortly with Bridgy or a 942.

I already have a single to 3phase output 440V digital inverter that powers the workshop cheaper than Transwave rotary convertor. So as Transwave above its just a matter of slapping a plug on the end, job done. Do have a 4KW Transwave rotary as well as backup, unused in 5 years so noisy its unreal and wont power 2.2KW lathe.

Is it just me, people have replied vfd this and that, where did they expect to put it - on back wall out of the way of debris? Remember access to start and stop immediately watching whats going on is a major requirement with remote pendant start/stop and variable pot. Not to mention loss of power feed and coolant, well you can just buy another vfd and transformer with switching.

Rob, Did you ever manage to resolve this issue. I have exact motor and would like to know the solution!

Hi Martin

In the end for my Bridgeport I bought a 1HP 240v to 415v VFD (with on/off/rev speed pot control pendant) from Drives Direct on ebay.

I did look at getting a rotary phase converter but I have limited space in my garage and found the flexibility of a VFD (variable speed) suited my needs better.

it has worked fine for the 3 years since I have had it.

Since then I have seen cheaper VFDs (240v - 415v) from ebay than the one I got from Drives direct.

Hope this helps

Thanks for the info on the 240-415v 3phase. Turns out , our local outfit that I brought my 220v VFD also sell a 415V model as well. So no need to change from star to delta. In my case, a ZX45 (RF45 clone), I am going to copy what I did on the lathe. So I will have braking on the motor for controlling the deceleration of the spindle, and control the initial start of the spindle at the same time. It will eliminate that rapid clunk of load on the gear box. But more important to me, is the use of micro switches to stop the spindle when setting a depth to tap to. It will just stop, and flick over to reverse and be quite consistent in the tapped hole depth. A bit like using a micro switch for thread cutting stop length on the lathe.

On the Bridgeport mill at work, the power feed motor,(X only ), coolant pump, lights and digital readout all come from a single phase supply. The 3phase is only for the spindle motor. It would be great if they could put a VFD on it, as it only has the belts and being able to adjust the speed at times is very handy. The other mills are Kondia with the Variable belt drive mechanism. I like them purely because of the variable speed. If a cutter chatters, just wind up or down until the chatter is gone is a great help.

Either way , there is no wrong way to get power to your mill, it just depends on what you want to spend. Some prefer to get 3ph on at their workshop, and then just use the gear like industry does normally.

Neil

That's what I did, and I have no regrets. Although expensive to install the cost of VFDs for larger motors up to 5hp gets expensive. The bungalow originally had a limited 60A single phase supply, so I used the upgrade to get a modern100A supply for the phase that is used for the domestic stuff.

On more specialised machines having 3-phase means I can run to the same limits as in industry. For instance the horizontal mill has three induction motors, spindle drive, power feed and coolant that I can run in parallel without problems. The spindle motor is Dahlander style for high and low ranges, so it'd be a pain having to reconfigure the VFD each time. Similarly on the Britan there are two electrical switches on the headstock to change spindle motor speed and direction. The can be operated in any sequence and at any time, even with the motor running. That would be difficult with a VFD. And there's an auxillary motor driving coolant and hydraulic pressure for power feed, both of which are useful. The motor also provides compressed air for the bar feeder, but I haven't used that so far.

My Bridgeport has the varispeed head and while it is convenient to wind the handle quickly to change speeds, that's all it is, convenient. I don't really miss having instant variable speeds on the other machine tools.

Andrew