nuisance tripping of 100 NSX Schneider MCCB

[Sparky 63]

Evening Gents

i have a 4 pole schneider mcb which keeps tripping intermittently the overload is set at 80A and runs in delta at around 40 A.The mcb supplies a 3 phase pump rated at approx 50kw-any one got any ideas what the problem could be .
cheers.

 

[telectrix]

Re: nuisance tripping of 100 NSX Schneider MCB

what type is the MCB?

 

[Bobster]

Re: nuisance tripping of 100 NSX Schneider MCB

What are you pumping?

What type of pump are you using?

Is is there anything common between it tripping?

 

[Darkwood]

Re: nuisance tripping of 100 NSX Schneider MCB

The circuit been designed by someone who is clueless about motor circuits... it will continue to nuisance trip because the mcb is not a good choice to cover a 50Kw motor regardless of mcb type or starting methods, you will be better using HRC fuses and its not a matter of matching the fuse to the loading of the motor, it doesn't work like that, you will need to have experience and knowledge in circuit design and the characteristics of the motor.


Anything exceeding 22Kw should not really be on an mcb and even a 22Kw would need a 63(d) mcb for a standard motor and starting duty... this brings big problems complying to Zs unless you oversize the cables.

 

[davesparks]

Re: nuisance tripping of 100 NSX Schneider MCB

100 NSX is an mccb not an mcb

 

[Sparky 63]

Schneider MCB tripping cont

Hi gents same question would you protect a 50kwpump motor with mcbs or hrc fuses
dripping

 

[Marvo]

Re: Schneider MCB tripping cont

Hi gents same question would you protect a 50kwpump motor with mcbs or hrc fuses
dripping

I'd protect it with a cover or build a pumphouse. Just joking, complete lack of info.

Softstart?
VFD?
Application?
Type of pump?
New install or existing?
Test results?

 

[Sparky 63]

Re: nuisance tripping of 100 NSX Schneider MCB

Yes that's right it is an mccb

 

[Sparky 63]

Re: nuisance tripping of 100 NSX Schneider MCB

Marvo star delta 3phase pump no soft start no vfd electrical panels new supply cable and motors are existing instillation

 

[Marvo]

Re: nuisance tripping of 100 NSX Schneider MCB

Two identical threads merged.

 

[davesparks]

Re: nuisance tripping of 100 NSX Schneider MCB

Is it the motor overload which is set at 80A or the overload setting of the mccb?

 

[Sparky 63]

Re: nuisance tripping of 100 NSX Schneider MCB

There is
A problem with both mccbs I was wondering could there Bea problem with a cable from the common feed being loose and while the circuit is cold there is no problem but when cables heat up the resistance will go up and possibly cause overheating overloading across 2phases and tripping the install action

 

[Marvo]

Re: nuisance tripping of 100 NSX Schneider MCB

There is
A problem with both mccbs

What do you mean by both mccb's? Why are there two of them?

I was wondering could there Bea problem with a cable from the common feed being loose and while the circuit is cold there is no problem but when cables heat up the resistance will go up and possibly cause overheating overloading across 2phases and tripping the install action

That's quite a wild theory. If there's a problem with a cable then you'd see evidence in the test results or during a visual inspection. If the cable is the correct CSA for the load then it won't heat up to a point where it's resistance changes significantly enough to affect the characteristics of the circuit.

 

[Marvo]

Re: nuisance tripping of 100 NSX Schneider MCB

Your posts so far are extremely confusing. Maybe rewind back to the beginning and tell us what there was before you arrived, what was the reported fault, what tests you did and why the cable has been replaced.

 

[Besoeker]

Evening Gents

i have a 4 pole schneider mcb which keeps tripping intermittently the overload is set at 80A and runs in delta at around 40 A.The mcb supplies a 3 phase pump rated at approx 50kw-any one got any ideas what the problem could be .
cheers.

Approx 50kW?
The nearest standard motor would be 55kW and have a FLC of about 105A at 400V.
It us usual on pump sets for the motor to be rated at close to the pump requirements.

Typical no-load current for a three phase cage motor is about a third of FLC. If the motor is running at 40A, that suggests that it is almost off load entirely.

Unless I'm missing something, your information doesn't add up.

 

[Darkwood]

The code didnt register the op gave but yes its an mccb ... OP used the term mcb ...totally different tripping curve ...I would consult tech of mccb and ask what recommended rating for motor is... also check if it has adjustable settings other than Amps ,they may be set up incorrectly...

This thread is lacking so much info it cannot really progress without the OP giving a detailed breakdown of all the points raised.

 

[Knobhead]

The OP hasn’t a clue what he’s talking about:

http://www.electriciansforums.co.uk/electrical-forum-general-electrical-forum/99267-inspection-testing.html#post1063966

Yet another chancer who thinks the internet will get him out of the mire.

 

[LeeH]

Am I correct saying not ALL of the compact NSX range has thermal protection? I thought some of them only have magnetic which isn't suitable anyhow.