Powering a 3 phase mill – bridgeport

[jason spencerParticipant @jasonspencer41535]

Hi all.

I've finally got a nice used rotary phase converter to power up my bridgeport mill.

I've a few questions though!

1; I take it the old 2hp bridgeports dont' have a neutral?

2; I've just got a cable with end cut off that connects to an emergency stop pedal, am i right in thinking that this will stop the machine working?

3,; would it be wise/safe to take the earth connection out of the 5 core 3ph cable going to the machine and creating an earth point in the power control box?

4; Anything else I should look for?

I've tried to power her up with the 3 phases connected but have nothing at all, Zero volts coming out of the connection to the head motor.

So close yet so far!!!

[jason spencerParticipant @jasonspencer41535]

[Les Jones 1Participant @lesjones1]

Hi Jason,
1 I do not know the answer to this question. It is unlikely the motor requires a neutral. If the coils on the contactors are 230 volts then it will be required. if they are 400 volts then neutral will not be needed. If in doubt trace out the wiring and post the schematic.

2 Emergency stop circuits normally use normally closed swiches. IF YOU ARE SURE THIS CABLE IS FOR AN EMERGENCY STOP SWITCH then the ends will need to be connected together for the motor to run.

3 There should be earth connections to the contol box, the machine frame, any metal boxes with switches or buttons on and the motor.

4 ????

Les.

[jason spencerParticipant @jasonspencer41535]

Les

Many thanks for your reply. I'm 100% its for an emercency stop switch, its connected into the isolator that you have to turn off to open the cabinet, its on a very long flex at the moment, I'm currently trying to track down a wiring diagram for the switch to be 100000% sure. Its very narrow diameter cable too.

[BazyleParticipant @bazyle]

I expect the contactor would be powered across two phases of the 3 phase and not a seperate 240 supply. One way to safely check out is to disconnect the actual motor winding and apply 12v from a battery charger through a car bulb to each pair of phases in turn. You can trace round the voltages and find which pair power the contactor as you throw the switches. If you 'activate ' the contactor the bulb will glow a bit but if you short something it will come on full.

Look around to see if there is a transformer not connected only to the lamp. It might be you have a 24v relay system in there too if the stop switch wiring is a bit thin.

Edited By Bazyle on 26/03/2013 13:46:01

[KWILParticipant @kwil]

jason, pm me with your email and I will send you a scanned circuit diagramme. For myself my Bpt is totally inverter run.

[jason spencerParticipant @jasonspencer41535]

KWIL- Pm sent.

Ideally I just working out which of the 4 wires I need to connect would be good just to help prove other parts of the machine.

[Les Jones 1Participant @lesjones1]

Hi Jason,
Are you now saying that the emergency stop cable has 4 cores ?

Les.

[jason spencerParticipant @jasonspencer41535]

Hi Les

Yes it has. I've managed to get the machine powered up by making a rig to hold in the spring loaded connectors, i'm not sure if they should have plastic covers on to hold them in?

[Les Jones 1Participant @lesjones1]

Hi Jason,
I think the thing you describe "as spring loaded connectors" is a contactor ( Just another name for a large relay.) The fact that you do not recognise it makes me think you should get someone with more knowlege to assist you to make sure what you are doing is safe.

Les.

[jason spencerParticipant @jasonspencer41535]

Hi Les

Having a look at the wiring diagram I can see that they're relays. School boy error.

I just need to work out why they're not operating, It must be due to the missing emergency stop. It'll be much easier if the diagrams were on one page.

[KWILParticipant @kwil]

Those diagrams will join up edge to edge so that they can be read as a whole. I am sorry that I do not have an A2 scanner to cover the fold out in one go.

[jason spencerParticipant @jasonspencer41535]

Kwil – sorry that wasn't a dig against your diagrams, just more reading them on the computer.

As before, very much appreciated.

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