Load sharing is used to distribute the mechanical or electrical load evenly among multiple drives or motors.
This ensures efficient operation, improved system performance & extended lifespan of equipment.
There are several techniques that can be used , one of the techniques is to set one drive as Lead in Speed Regulator & the follower drive as Torque regulator.
When running two motors that share the load, both should not be run in speed regulation.
If not the drive tend to fight each other to be the lead drive. This can lead to motor overheating, poor performance & premature failure.
The follower drive can have different modes to run as a torque regulator:
Direct or Straight up torque. The follower/slave drive just follow the torque command from lead drive. Used only for non slip shared load.
SLAT Min & SLAT Max. SLAT mode stands for “Speed Limiting and Adjustable Torque.”.
These are torque regulation modes that automatically switch smoothly to speed regulation in certain condition such as web break or slippage.
Here’s a step-by-step guide to setup it in Allen-Bradley Powerflex 750 drives & Control Logix PLC:
Configure the Hardware:
* Install the PowerFlex 755 Drive
* Set Ethernet IP Address
* Add & wire Encoder card
* Wire the drive power, connection to the motor, Safety & Isolation:
Configure the PowerFlex 755 Drives using Connected Component Workbench Software.
The lead drive needs to be in speed regulation mode P[309]
Set on both drive:
a) Drive Control Mode P[35] to Induction FV (Full Vector).
b) Speed Unit P[300] to RPM
c) Primary Speed Feedback P[125] to Encoder & set Encoder PPR
d) Enter motor data
e) Stop Mode P[370] to Ramp
f) Direction Mode P[308] to Bipolar
g) Speed Reference P[545] to Port 13 Reference (Ethernet)
h) DI Enable P[155] to corresponding Digital input.
i) Decel Inhibit Action P[409] to Ignore
j) Acceleration & Deceleration rate value same on both drives (eg. 10 seconds)
k) Set Embedded Ethernet Data Links at Port 13-Ethernet/IP for additional data that will be wrote & read to PLC
Use Wizards to do Direction Test, Autotune & Inertia tune. If both motor mechanically coupled to the same load, then the total inertia value P[76] need to divide in half.
Configure the ControlLogix PLC
Using Studio 5000 Logix Designer software, Add Ethernet Module for Communication Card in I/O Configuration & set the IP Address
Then create New Module ‘Powerflex 755’ for Lead Drive & Follower Drive under Ethernet Network.
– Key in Name, IP address, Revision & Drive Rating in Identity tab under Defice Definition.
– Add Encoder in Peripheral Tab
– Fill data that will be wrote & read from Powerflex Drive in Connection Format
Create Logic for Load Sharing
Download and Run the program.
That’s it. Plan to implement Load Sharing?
