pump motor tripping while stopping

[jithin john]

A abb squirrel cage 3 phase induction motor 415V ,585A ,1455 rpm coupled to a kirloskar multi stage pump with h=320m,q=216m3/hr power 215kw ,rpm 1487 is tripping while stopping the pump.
While stopping the motor the current reading is going high and motor is going to trip(please check video)
please tell the possible reasons for this issue

 

[itsmoked]

How about some more details..

Has this always been the case?
New installation?
Or, did it just start happening?

Does "STOP" cause any more functions to happen than ONLY stopping the motor? Like valve openings or closings?

Is the motor fed thru any kind of reduced voltage starter?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Without a circuit diagram, let's start guessing.
My guess is that this pump is controlled by a VFD with a too aggressive de-celeration curve.
OR
Does this motor have PF capacitors directly connected to the motor?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

PS:
Please don't forget to post a diagram.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

No, not a VFD, because that would likely have a display and tell you that it was tripping on over VOLTAGE from too aggressive of a decel ramp. The current goes UP when you stop it, which is indicative of this having a Soft Starter on it, and the Soft Stop function is being used to try to mitigate water hammer. In that process, voltage is slowly choked off to the motor to let it slow down gently and current will go up until the valve closes and cuts off flow. In this case the settings of the decel ramp are incorrect. Most likely the decel ramp time is set too long and/or your check valve is not closing.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[RRaghunath]

What protection is causing the trip??
Could it be that thee is back flow of water as there is no non-return valve in the discharge pipe and this causes motor stall protection to issue trip command!!
You may have to verify the protection settings!

 

[itsmoked]

Why would that scenario have the current going up Jeff? I'm not following how a choke-off ups the load.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

As voltage goes down the motor slip goes way up. A lot of slip = high current on an induction motor.

 

[jithin john]

Thank you every one for your replies.

Itsmoked :this was not always the case .the problem arises before 5 to 6 months and our company just got the new maintenance contract
this pump is operated through scada and a mov is also there after discharge and is always kept open

waross: There is a soft starter siemens sirius ss3 (picture attached ).I dont have a wiring diagram and iam pretty sure even the client doesnt have one

Jraef:spot on .there is a surge vessel and was not functioning properly .But i rectified it yesterday and then also the issue persists.

rragumath.there is a nrv available and pretty sure it is working

 

[jithin john]

https://files.engineering.com/getfi...-86d32e710b2b&file=IMG_20191006_121537153.jpg

https://files.engineering.com/getfi...-c1346359f27a&file=IMG_20191006_121513635.jpg

 

[Parchie]

@ jithin john,
The deadfront is preventing us to see the innards of that thing!
AFAIK, one causes of tripping a pump motor when stopped is a failure of the discharge check valves; especially if the head handled by the pump is high and long!. The backing media could drive your motor back and trip it if you have a starter that tries to decelerate the motor before cutting off the motor supply voltage.
I even experienced a whole pump assembly that flew apart due to tremendous forces of a runaway impeller.

 

[itsmoked]

Thanks LHutz.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Bijoyq8]

I agree with Parchie about the backing media being able to drive the motor back and create a stall situation .
Infact I too have experienced situation where a severe mechanical shock resulted in twisted and badly damaged the pump shaft .

Jithin please check and let know

1.The parameter setting for coast down time and coasting method set in soft starter.

2.Is the coast down time presently set at zero to "overcome" tripping ?

3.Why the MOV at discharge is always kept open.