200 HP 236 FLA 480V Tripping out

[compman72]

I have a 200 HP motor connected to a Fuller Kinyon Pump that will run fine at 130 amps and when we try to increase material flow to the pump - and try to obtain 175-200 amps it will not do it. Anything over 130 amps will cause the amps to go to 400-600 amps and trip out. The motor has been meged. The age and history of the motor are unknown. All of the safety settngs have been tested.
I appreaciate any and all advise.

 

[aolalde]

You must give the voltage to have a reference, in USA the most common industrial voltages for 200 HP are 460 Volts with full load current around 240 Amperes or 575 Volts and current around 192 amperes.

A possibility is that you have a delta run motor connected wye . That results in a weak magnetic field and the motor stalls when the load is increased. The locked rotor condition increases the line currents several times in spite the low voltage.

 

[rbulsara]

Unless the nameplate of the motor is wrong, a motor does not draw higher current for no reason. I suspect there is notning wrong with the motor. The "load" or the "material" is causing the overload. This sounds like a classic case of blaming the symptoms rather than finding the cause.

What is that you are pumping? Increasing the flow may have other fluid dynamic chages (increase in head) that stalls the pump and the motor. Is the density of material consistent with pump and motor sizing? What is the rated flow of the pump? what is the current flow rate?

May be the 'recipient' of the pump material is not too happy when you try to increase the flow and causing the back pressure.

 

[rbulsara]

good point aolalde.

 

[itsmoked]

How are you attempting to increase the current?? VFD?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[compman72]

It is a 460v motor. The material being pumped is cement from a rail car. The feed is controlled by a hand operated flow control valve.
Yes, there is a Benshaw soft start system as well.

 

[rbulsara]

ahhh, cement!! Is it a blower or a vacuum pump?

Just a soft start or adjutable speed as well?

I just think the pump is not rated to pump more than it does now. You may have oversized motor on it, but the "pump" gets clogged as soon as you add more material. Look at the pump rating, speed, differential pressure, flow etc and compare to the acutal and not at the motor yet.

 

[itsmoked]

You say cement... So since you didn't say concrete you must be referring to dry powder transfer. Is this a vacuum pump or a blower??

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

It's a screw auger type of pneumatic pump used for Portland cement (dry powder) transfer. Amp draw should be roughly linear with load increase.

compman72,
I think aolalde has a very good point, but if you don't understand what he meant I'll give you the brief rundown.

Many large motors are designed for what is called Y-Delta starting, a way of reducing the starting torque and current on startup by using a 2 step process. In the fist step, the motor windings are connected in a Wye (Star) pattern, which provides only 33% of the torque but also reduces the starting current to 33% or normal. Then after the motor is nearly at full speed, the winding pattern is switched to Delta which provides full torque.

Y-Delta starting is very problematic and a lot of people choose instead to use solid state starters such as the Benshaw unit. The problem aolalde mentioned would be that at some time in the past when someone swapped out the Y-Delta starter, they mistakenly connected the motor to the Benshaw starter in the Y pattern instead of Delta. So all along, you probably have been operating that motor in the reduced torque mode, i.e. 33% of full capacity. That has apparently been fine up until now because your flow demand has been low so nobody noticed, but as you now try to increase flow, the motor torque is so low that you are stalling it almost immediately.

The numbers add up to point to this problem as well. If you were stalling a 200HP motor properly connected (in Delta), the Locked Rotor Amps could go as high as 1440A. If however as you say, it is going to +400A, guess what? 1440 x 33% (Wye connected Locked Rotor Amps) = 475A!

Have a qualified motor shop or an electrician familiar with Y-Delta motors take a look at the motor connections.

JRaef.com
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