Subject: Synchronizing Two 4kW Motors with AltiVar VSDs - Seeking Recommendations Hello there, I am looking for guidance on synchronizing two 4kW motors, each connected to its own AltiVar Variable Speed Drive (VSD). These motors are tasked with pulling cables via a pulley system, and when they are under load, I experience slip, which causes variations in speed. To manage this system, I am utilizing an Omron CP1L-EM PLC along with two Omron Rotary Encoders (model E6C2-CWZ5B with 360 pulses per revolution) — one for each motor. My main query is regarding the optimal approach to reading the pulse signals from the rotary encoders and converting them to RPM. Here are a few methods I’m considering: 1. **Using PRV or PRV2 (Instruction 883)**: This method seems ideal as it allows for direct conversion to RPM. However, can I apply this instruction to both Counter 0 and Counter 1 simultaneously? 2. **Reading Raw Values from Counters**: I could read from Counter 0 (A270 for motor one’s encoder) and Counter 1 (A272 for motor two’s encoder), convert the raw pulse counts to RPM, and then compare the values to make necessary adjustments. 3. **Employing the CTBL Instruction**: Would the use of the CTBL instruction be beneficial in this synchronization scenario? Once I accurately obtain the RPM for each motor, my plan is to implement a comparison logic to detect any discrepancies. If a mismatch occurs, I would send a scaled analog output to the VSDs to adjust the speeds as needed (within the range of 10-50 Hz). I would greatly appreciate your recommendations on the best course of action. Any assistance would be invaluable. Thank you!
Explore the discussion thread regarding synchronizing two motors using a CP1L-EM and Omron rotary encoders at the provided link. The insights and solutions shared in this forum can enhance your understanding and implementation of motor synchronization techniques.
When considering how to approach this task, it's important to clarify a few key factors. First, determine whether you are dealing with a lifting application or a rolling load scenario. Are you operating with two motors that need to lift or pull a shared load (known as load shearing)? Alternatively, are both motors working on independent loads that must maintain the same speed? Next, consider how speed commands are generated for the drives. Will these commands originate from a Programmable Logic Controller (PLC), indicating that the movement speed may vary due to PLC adjustments (not simply matching speeds)? In either case, I recommend removing synchronization from the PLC. Utilize the PLC primarily to direct both drives regarding operation direction and, if needed, to set the commanded speed. For load shearing applications, employ a master-slave torque follower configuration. Here, the PLC controls the speed of the master drive while the slave drive is configured to follow the torque of the master—not its speed. It's advisable to set the slave drive's speed to approximately 10% higher than that of the master. Note that using encoders on either drive may not be necessary unless precise speed matching with external references is required. If the loads are independent yet must operate at the same speed, use two high-quality flux vector drives accurately configured for identical speeds and acceleration/deceleration profiles. Synchronization with external devices isn't necessary; if both drives are set up identically, they will naturally run at the same speed. Regarding encoders, you've mentioned a resolution of 360 Pulses Per Revolution (PPR), which might be on the lower side. For optimal control, I recommend at least 1024 PPR—higher counts enhance control performance significantly. Lastly, in both configurations, ensure you implement an interlock between the two drives. This is crucial: if one drive experiences a fault, the other should be automatically halted to prevent load dropping incidents. I've successfully executed both methods numerous times, and each has proven effective, but careful selection based on your specific application needs is vital.
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