Phase To Phase Voltage Should be zoro volt

As routinely mentioned here on CR4, need more information.

Are you measuring phase to phase at the welders?

What is the Phase to earth or neutral voltages like?

Have you checked for loose or poor terminations, and was this check done while loaded, that is welding?

If you are not suitably qualified to work on electrical items, please seek help from some one that is.

Rgds Trevor.

Yes more information please.

I am curious what made you test the voltage between two welders in the first place?

Normally a check between the phases on one machine would confirm correct connections and voltages. or are these paralleld welders suppliying one SAW unit?

Yes, these both welding machines are using for parralleling application,each machines is rated for 1500 Amp & we need 3000 Amp Current for welding,so we paralled both machines.one welder set as a master machine & other as a slave.

It is nessesary,

that the input voltage to the paralleled machines are in phase. test results should be as follows.

L1 Master to L1 Slave should be 0 volts

L2 Master to L2 Slave should be 0 volts

L3 Master to L3 Slave should be 0 volts

But when we checked found following observations,

L1 Master to L1 Slave found 40 volts

L2 Master to L2 Slave found 40 volts

L3 Master to L3 Slave found 40 volts

Due to during welding one machine gets more input current as compaire to onother due to that phase gets imbalanced & one power source trips immedeately.

As your voltage difference is the same on all 3 phases it would seem that one of your machines supply is coming from a source which is underrated or supply cables are not large enough. Have you measured between phase voltages on each machine if one is lower than the other then this observation would indicate something like this.

Input supply voltage to both machine is,

welder 1- RY,YB,RB = 405 VAC

WELDER 2- RY,YB,RB= 405 VAC

Are these voltages being measured when machines are operating or off load??

Yes, these voltages are measured during off load condition.

If these voltages are the same at each machine I cannot see how you would have a voltage difference on like phases unless you measured this when the machines were running which would indicate supply problems on one line.

You are supplying the machines with two cables?? not looping out of one to the other?

Do you have the master & slave links set correctly in the machines?

With the machines are off load. the current through the input cable is zero (or very near it, only the no load current)

Is it a generator type? Can you check up the phase current drawn on noload ? a simple tong tester will do.

Still a 40V differential drop is a bit too much unless there is high contact resistances at either or both ends of the cable lugs.

Interesting... I would suspect there is a phase shift occurring. The assumption was that you were measuring the supply to the welders, primary side, and this was coming from the same distribution board. Is this correct?

Are the welders identical?

Is there something different like capacitors or inductors on one to the other?

A quick calculation puts the phases on welder 1 out by 5 degrees to welder 2.

Somthing does not compute!!

supplies are coming from same distribution board.

Need answer re measurment conditions.