Grasso Tripping breaker

[maltaf]

I went through problem with one of Grasso compressor its W series with 450Kw motor
problem is it is causing the breaker to trip when it shifts itself from star to delta.
Following things checked.
Motor insulation is okay
Cable insulation is okay
Star timing extended and motor working fine
All things contactors, breakers checked,swapped everything fine.
When motor decoupled it was working fine (Shifting properly from star to delta)
Slide calibrations done found normal.
Can anybody help me on it

[RANGER1]

maltaf,
Some other possibilities could be mechanical.

To much oil in compressor (overfilled, suction check valve failed.
To much oil in compressor oil separator
GEA usually recommend minimum 10 minutes between starts due to oil pump filling up machine.
Compressor not fully unloaded, check above, recalibrate again.

If above okay & not already the case, lower compressor package, oil separator etc to suction pressure to help for easier starting, less start up load.
Sometimes a line exists to do this when compressor off, a line small between discharge & suction cracked open.

[Brian_UK]

Also check that the breaker is not failing.

[Grizzly]

Hi it might be worth if you have not already done so. In checking the timer unit that switches over the Star, Delta contacts. If the switch over is not clean then the resultant Load especially from the star contact, can take the breaker out.
Just a thought. as i have seen this before.
Cheers Grizzly

[maltaf]

Thanks for your reply

THERE IS NO OVERFILLING OF OIL.
OIL IN THE SEPARATOR IS 1/3 OF GLASS
ADJUSTED DELAY WAS ALREADY 10 MINUTES
TRIED CALIBRATIONS AND RECHECKED AND FOUND NORMAL
ONLY THING LEFT IS THE CHECK VALVE

[maltaf]

breaker replaced with other one , it is okay

[maltaf]

but it is working fine when motor decoupled.

[RANGER1]

maltaf,
Has this machine been running in the past & now has a problem?
Or is it new compressor package.

What is suction & discharge pressures in system & package itself at start up.

[Grizzly]

Hi All of the above by Ranger are relevant!
Just a thought have you put a Clamp meter on the incoming supply to see what the Comp is pulling Amperage wise?
Star Delta timers are normally around 7 seconds duration. Just as a question which Breaker is Tripping?
What is your oil temp by the way on start-up?
Good luck Grizzly

[RANGER1]

Maximum oil pressure 350 kpa above discharge pressure at all times, otherwise damage may occur mechanically.
If compressor not connected, of course no problem, as no load on start up.
Calibration of slide valve always best when compressor running.
So could still be an issue.

[maltaf]

maltaf,
Has this machine been running in the past & now has a problem?
Or is it new compressor package.
it was running earlier.

What is suction & discharge pressures in system & package itself at start up.
suction pressure 2.25 bar discharge 12.0 bar

[maltaf]

Hi All of the above by Ranger are relevant!
Just a thought have you put a Clamp meter on the incoming supply to see what the Comp is pulling Amperage wise?
Star Delta timers are normally around 7 seconds duration. Just as a question which Breaker is Tripping?

What is your oil temp by the way on start-up?

Good luck Grizzly
main breaker. If we extend the timing breaker from substation goes trip.
oil temp 36C

[knighty]

check the amp draw while it's starting up in star before it switches to delta?

[Grizzly]

Just a thought have you put a Clamp meter on the incoming supply to see what the Comp is pulling Amperage wise?
Great minds think alike?
That's exactly what i was trying to imply. You can get a huge inrush between switching contacts.
main breaker. If we extend the timing breaker from substation goes trip.
Not sure what is meant by this? 10secs as previously mentioned is already on the long side.