2-phase resistance welder MCB

[craigdiver]

I'll take a some photos tomorrow and post so you can cringe at the setup!

 

[davesparks]

In a way that is good, it strongly suggests the problem is the fact that an MCB has been installed where it shouldn't be.

 

[Darkwood]

Sounds ideal for an energy track system ... if it ever seems a plausible option either add to thread or PM me and ill suggest some ideal systems where they may even come out and do a free quote and select all the correct gear for you ...

I still stick quotes in and ask them to review the past 5yrs maintenance costs for the existing including Electrical, coolant issues etc all associated with the existing problematic set up ... I bet it will open their eyes just how much its costing them and what they could be saving.

 

[craigdiver]

In a way that is good, it strongly suggests the problem is the fact that an MCB has been installed where it shouldn't be.

my experience is that MCBs are a modern replacement to fuse links if properly rated. It appears on this installation that the design current (which I think should be the primary current whilst welding) greatly exceeds the MCB rating. Others with more experience in resistance welding may know better and I welcome their wisdom?

 

[davesparks]

I'm afraid your are wrong, MCBs are not a replacement for fuses. They are an alternative which give a level of convenience in being easily resettable.
Both fuses and MCBs have their place in this world and it is up to the person designing an installation to select the correct one for the job.

In your situation it appears that the designer selected fuses which have been doing the job fine and then someone else added an mcb which hasn't been so great.

 

[craigdiver]

In your situation it appears that the designer selected fuses which have been doing the job fine and then someone else added an mcb which hasn't been so great.

Definitely an add on, a pretty din rail enclosure between a 20+ year old isolator and welding controller.

 

[Knobhead]

Cooling water? Are they Lincoln welders?

 

[craigdiver]

I should publicly flog myself for my way off the mark fault finding. eventually traced to breakdown of insulation on welding transformer, resistance measured fine (8.3 ohms) but shorts out when meggered. PW welder 25+ years old and encapsulated transformer obsolete.

 

[Darkwood]

shorts out to what ! .... its a low impedance coil it will show dead short if meggered ... thats the way your post reads or do you mean to earth?

 

[Darkwood]

Cooling water? Are they Lincoln welders?

Just plug topped 4 of these replacing some 50yr old American brands .... the old are still the best for durability

 

[craigdiver]

shorts out to what ! .... its a low impedance coil it will show dead short if meggered ... thats the way your post reads or do you mean to earth?

as you quite rightly state that does not read very well, shorting to earth

 

[Robotstar5]

We had many hundreds of resistance welders in BIW (body in white) at Longbridge and very few problems on primary side, it was the secondaries that took the hammering, some of the failures were quite impressive due to the current involved .
Generally fed them with motor rated fuses, 100M160A etc.