Contactors lost continuity

[u2v2w2]

What could be the reason for all of the three Siemens contactors on a 37kW star delta starter to lose continuity on auxiliary contacts and main contacts all at once? Probably the best thing to do is to replace them since cleaning would be too fiddly.
There are no signs of water intrusion only minimal dust.

 

[DPG]

I'm no expert here, but all the contacts and aux contacts cannot have failed at the same time. So presumably the contactor is not fully pulling in?

Sorry, have just read the post again. Are you saying this has happened to all contacts on 3 separate contactors? Really?

 

[Petej999]

What could be the reason for all of the three Siemens contactors on a 37kW star delta starter to lose continuity on auxiliary contacts and main contacts all at once? Probably the best thing to do is to replace them since cleaning would be too fiddly.
There are no signs of water intrusion only minimal dust.

stop button not being reset properly. control fuse open circuit, burnt contacts, the list is endless

 

[u2v2w2]

I'm no expert here, but all the contacts and aux contacts cannot have failed at the same time. So presumably the contactor is not fully pulling in?

Sorry, have just read the post again. Are you saying this has happened to all contacts on 3 separate contactors? Really?

Yes all three contactors. Actually it seems like they aren't pulling in fully, but there is no continuity on all of the NC contacts as well whatsoever.

 

[DPG]

Yes all three contactors. Actually it seems like they aren't pulling in fully, but there is no continuity on all of the NC contacts as well whatsoever.

What voltage do you have across the coils when they should be activated?

 

[u2v2w2]

stop button not being reset properly. control fuse open circuit, burnt contacts, the list is endless

Other low power contactors around are working.

 

[u2v2w2]

What voltage do you have across the coils when they should be activated?

110VAC. No voltage at the start button.

 

[DPG]

110VAC.

And are they 110V coils?

 

[Petej999]

What could be the reason for all of the three Siemens contactors on a 37kW star delta starter to lose continuity on auxiliary contacts and main contacts all at once? Probably the best thing to do is to replace them since cleaning would be too fiddly.
There are no signs of water intrusion only minimal dust.

What about contact pitting????, is there a regular maintenance regime?????

 

[u2v2w2]

110VAC. No voltage at the start button.

Seems like for some reason the start button is wired trough NC auxiliary contacts. Probably will have to revire the whole thing. For some reason owner keeps bringing in machinery with control panels in poor condition where someone else has been fooling around with the wiring or taken from other machines which needs to be rewired most of the time. Sometimes that's the quickest way to get them working.
The main topic stays the same: complete loss of continuity on all three contactors.
No open or short circuit on the coils.

 

[James]

Any mechanical interlocks on the contactors that are either active or stuck?

 

[u2v2w2]

Any mechanical interlocks on the contactors that are either active or stuck?

There are no mechanical interlocks. Could it be that the contactors are only allowed to move halfway in between the engaged contacts and disengaged resulting in no continuity on both NO and NC contacts? The fact that the owner keeps telling again that he is sure he has seen the machine running before he bought it adds to the mystery.

 

[LeeH]

Are you sure there are no interlocks?

 

[u2v2w2]

Are you sure there are no interlocks?

Yes. Majority of star delta starters coming my way have been without mechanical interlocks so far. Still seems like all three contactors have slightly more limited range of motion than typically. Although they seem to be retracting fully enough for NC contacts to theoretically engage.