two motors driving 1conveyor but drawing different currents 2

[chumet1]

i have two 250kw motors driving 1conveyor bt installed on different pulleys. One is drawing 200amps and the other around 90amps. Full load current is 325amps for both motors. I am concerned that only one is working and might end up failing prematurely. Is it normal or should be rectified

 

[jraef]

If the motors are EXACTLY the same, i.e. same manufacturer, same part number, same manufacturing batch, then that much of a difference indicates a likely difference in the power transmission system, meaning the belt tension or grip. That should be looked at. If the motors are NOT identical, then even a slight difference in slip percentage will make one of them pull the other as a load. That will even out as the external load increases and the slip increases on both motors, but maybe that much. If on the other hand the values you are stating are under full load conditions for your operation, I wouldn't worry about it if you are only drawing 200A on a motor rated for 325A FLC. I would however question the need for the 2nd motor in that case.


"Will work for salami"

 

[rhatcher]

I will add to jraef's answer that a small difference in slip between two different motors of the same rating (same hp/kw but different rated full load speed/slip) sharing the same load can result in a large difference in motor load amps. This is because of the very steep speed/torque curve between rated load and breakdown torque for most motors.

Alternatively, two identical motors on the same conveyor but in different locations could, in my opinion, take a different share of the load depending on placement. The one at the beginning of the conveyor, next to the rollover pulley, would take take the majority of the load while the one located at the middle or end of the conveyor would see a lighter load. The difference is because the conveyor belt is elastic.

 

[chumet1]

thank you for you support. The motors are arranged as rhatcher has stated with the motor drawing the larger current closer to the head pulley. Some modifications were however done on the motor drawing lower current. The original motor had its rotor shaft fractured and replaced with an equaly rated mor which had a spark in its stator windings and also failed. So we put together the stator and rotor from the 2 motors and built one which is now drawing less current

 

[chumet1]

thank you for you support. The motors are arranged as rhatcher has stated with the motor drawing the larger current closer to the head pulley. Some modifications were however done on the motor drawing lower current. The original motor had its rotor shaft fractured and replaced with an equaly rated mor which had a spark in its stator windings and also failed. So we put together the stator and rotor from the 2 motors and built one which is now drawing less current

 

[rhatcher]

Did the two motors share the load (have the same current) before the second motor failed? Did the current increase on the motor near the head pulley when the modified, motor was installed? Were the two failed motors that were used to make the modified motor the same manufacturer, model, and rating?

 

[waross]

With a vee belt drive, worn belts or tight belts may ride deeper in the grooves and change the drive ratio slightly. Worn and tight is even worse.

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

 

[rhatcher]

good suggestion waross. The OP should add this to his list of questions to answer and things to check.

 

[PersonalProfile]

As stated by others, it is unlikely they will perfectly share for various reasons. This does not mean that this arrangement can't work (there are plenty which do).

This may be of interest:

http://www.littelfuse.com/technical...s/Technical Articles/Conveyor Belt Drives.pdf

Regards,
Lyle

 

[chumet1]

thanx joined19072011, that article you sent was of good use. i think i just found my answer