# Load Sharing problem



## k4trozz (Dec 3, 2013)

Hello all,

I'm a newbie in this area. I have a problem when performing load share with the VFD. Load share succeeded when the VFD frequency input to the motor is positive. Output torque on each motor is positive. When the input is negative, the load share failed because the slave motor torque issue a negative value and issue a fault overbraking.

Here's my arrangement of motors for load sharing. 










2 motors connected each other to move single (gray) shaft. Motor 1 act as the master and the rest as slave. I'm using 30kW WEG asynchronous speed AC motors and Schneider ATV71 VFD.

please help me, my head already want to explode think about this. :wallbash:


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## JRaef (Mar 23, 2009)

k4trozz said:


> Hello all,
> 
> I'm a newbie in this area. I have a problem when performing load share with the VFD. Load share succeeded when the VFD frequency input to the motor is positive. Output torque on each motor is positive. When the input is negative, the load share failed because the slave motor torque issue a negative value and issue a fault overbraking.
> 
> ...


How have you done this, you are not clear. Is it one drive running all 4 motors, or one drive per motor, with DRIVE #1 being the master and the other DRIVES as slaves?


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## k4trozz (Dec 3, 2013)

JRaef said:


> How have you done this, you are not clear. Is it one drive running all 4 motors, or one drive per motor, with DRIVE #1 being the master and the other DRIVES as slaves?


sorry I've forgot to tell you. It's 1 drive per motor. Drive at motor 1 act as master and the rest is slave.


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## JRaef (Mar 23, 2009)

Ok, so do you have drive one (master) set up as a speed follower to your control signal, then have the slaves set as torque followers to the master? The slaves have to be torque followers, not speed followers. If so, what are you using as the signal off of the master to the slaves? If you want braking, you need to set it up for a negative sign reference. If using 4-20mA, that means conditioning your signal to be 12mA at zero torque, 20mA at +LRT, and 4mA at -LRT.


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## AllClear (Dec 31, 2013)

Had nearly the same issue you are describing. We Have 2 450hp motors on Altivar 71's turning a mile long conveyor belt. We Tried several different methods to control them. Currently i believe we are in simple volt/hertz and tweaked some obscure parameter, It Finally Runs Perfectly Again.


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