Vfd For Air Classifier In Cement Plant

Dear All,

Does anyone knows about the operating behaviour of this application?

i'm mentioning below the details i got from the customer:

It is a fan, motor rating 75Kw, gearbox between motor & fan, starting with damper open, altitude 1600 to 1700 m.

Whether we should consider starting duty as 120% or 150%?

Thanks & Regards,
Gaurav

Input Protection Scheme For Msf

Dear All,

MSF manual suggests on using normal fuses for short circuit protection of MSF.

There is no ground fault protection in MSF.

Question is , whether we can use MCCB , 3 pole with adjustable O/L, S.Ckt & ground fault protection or as O/L protection will be provided by MSF itself, wecan use normal HRC fuses along with ground fault relay/ monitoring relay.

What i know is that the earthing scheme used in the installation effects the choice of ground fault relay.

Except this what other protection is ideally required at the input of MSF for trouble free operation, as i recently faced a major failure & even the customer was not forthcoming on the events prior/during the fault.

Thanks & Regards,
Gaurav

Analog Output Resolution

Dear All,

i would like to know , what is the resolution of analog output of MSF?

purpose is to connect this analog output to a plc.

What other points one should consider for wiring analog signals?

Thanks & Regards,
gaurav

Motor Brnout/softstarter Failure

Dear All,

Recently faced a problem.

Some 6 months back installed a softstarter; current rating 710A on a 350 Kw motor; paper mill refiner application.

Two days back got a message that the motor has burnt & softstarter is unable to start the replacement motor of 250Kw Rating.

History of events as told to me:
During a normal running( motor was running on a bypass contactor) the motor stopped , the main circuit breaker tripped. Breaker was reset & motor checked.
Again restarted & after sometime there was smoke coming out from motor.

On seeing the motor , it was completely burnt & most probably the point where the windings were brazed has blown off.

When i tried to start the 250Kw motor, decoupled from load;

the motor shaft took 2-3 turns then stopped, again 2-3 turns & stop........
during this time the current values were oscillating from 144-185-212, 144-185-212.....
i increased the initial voltage level from 30% to 60% in steps of 5% but to no use.
I also measured resistance values betweeen input-output terminals fof S.S for each phase, readings were Rphase 2.71 Mohm, Y phase 2.72 M ohm but in case of third phase the readings never stabilized as soon as reading approached 3.7.. the tester again went into scanning mode.

During one of the trials on the 250Kw motor, the move & stop pattern of motor was going on, bypass contactor went on , motor started & eventually the main circuit breaker tripped.

Any possible explanation for this behaviour.

Thanks

Msf For 315 Kw Feed Water Pump &315 Kw Id Fan

i have an enquiry for MSF for 315 Kw feed water pump &315 Kw ID fan,with inside delta connection to motor.

Customer is also keeping a star-delta starter, as an option if soft starter fails.

What i know is that MSF cannot be used for inside delta condition.

Then what is the solution keeping in mind that customer wants minimum time taken for him to transfer from softstarter to star delta, in case of any problem with softstarter.

Can we divide the output supply from softstarter into two parts( using contactors in these two output partitions) & give them into six leads to motor, with necessary phase reversals, & interlock this arrangement with star delta starter.

Will , all the benefits of starting viz. linear & quadratic torque profile valid in this condition , protections.

Customer is using above mentioned arrangement for VFDs.

Please suggest.

Thanks & Regards,
gaurav1981