Bridgeport contactor circuit /isolator issues

[jason spencerParticipant @jasonspencer41535]

I've a bridgeport mill(1969ish) that i'm trying to get powered up. It seems that the issue I have is that the relay/contactor circuit won't energise, I think that its an issue arrising from the main isolator.

Does anyone have a diagram of the isolator switch they use?

It has a 4 core(3 phase/1 earth) cable connected to the isolator where an emergency stop switch should be.

I'm going to guess that if I can get a diagram for the isolator I can wire the footswitch out which should energise my contactor circuit? Or wire out the isolator totally?

The mill is running of a rotary phase converter.

[jason spencerParticipant @jasonspencer41535]

Bridgeport contactor circuit

[Les Jones 1Participant @lesjones1]

Hi Jason,
I have had a look at the schematic that Kwil sent to you. The main isolator will just be a three pole switch. As you had the spindle motor running by holding in its contactor the three phases must be getting through the isolator. Kwil's schematic does not show any emergency stop wireing so there must be variations between different batches of machines or the emergency stop was fitted after manufacture. You will have to trace where the wires connect to. If the schematic is the same as your machine then the contactor coils run from 110 volts. Have you verified that there is about 110 volts on the secondry of the transformer ? If not then check for continuity of phases L1 and L3 between the power input and the primary of the transformer. If the 110 vols is OK the use the diagram on the right of the drawing to trace continuity between the 110 volt secondry of the transformer and the contactor coil. There should be continuity between one side of the coil and the transformer secondry all of the time. On the other side of the coil it will only show continuity when you HOLD IN the start button or hold in the contactor.

Les.

Edited By Les Jones 1 on 29/03/2013 20:09:11

[Clive FosterParticipant @clivefoster55965]

 

A common way of implementing emergency stop functions is to put a normally closed switch in series with the stop button wiring to the contactors. I have a 1977 wiring diagram which clearly shows the stop button and overload switches for all the contactors connected in a series string running from one side of the transformer to the start button and one side of the coil. Clearly its no problem to break that line for an emergency stop switch. I can easily E-Mail you a PDF if it may help.

The contactor coils will only receive power if all the normally closed contacts are making good connections. The overload system isn't completely reliable when it gets old. Probably because it (almost) never operates and doesn't get exercise. If you have the auto / manual reset selection type its worth operating the selector a few times whilst spraying with a good quality switch cleaner. That cured mine when the head motor contactor went on strike. You need a clear head to figure out where to probe to check the circuits for breaks. If need be the overload units can be removed for servicing on the bench but its aright faffle to get things out and back.

Also worth making sure that the transformer is connected to across the mains powered legs of the rotary phase converter. Theoretically an RPC gives adequate three phase output regardless of the terminals used but its not uncommon for the control side to be iffy, if not fully non-functional, when the generated leg is used. Friend Mike had a pukka Transwave RPC to run his Bridgeport and had continual random starting problems until we got things connected the right way round. Not only did the transformer have to be across the mains input legs but it and the head motor also had to be connected the right way round before it became completely reliable.

Clive

Edited By Clive Foster on 29/03/2013 23:25:25

[Les Jones 1Participant @lesjones1]

Hi Jason,
I see from another thread that you have fixed the problem with your Bridgeport. What turned out to be the cause of the problem ?

Les.

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