Application Constraint
Two asynchronous motors, each supplied by its own PChV2 drive, act through a gearbox on one mechanically coupled shaft. The master must regulate shaft speed while the follower contributes torque as the process load increases.
The rigid mechanical connection forces the driven outputs to the same mechanical speed, but it does not guarantee equal motor torque. Differences between motor parameters and slip can cause one motor to carry most of the load or drive the other motor regeneratively.
Why Equal Frequency Commands Are Insufficient
Sending the same frequency and run commands to both drives establishes similar electrical speed references, not controlled load sharing. Asynchronous motors can develop different torque at the same commanded frequency because their parameters and slip differ.
Current or electrical power alone is also an indirect sharing variable. Mechanical power follows P = T × ω, but measured electrical power includes motor losses. Current likewise does not establish equal electromagnetic torque without a supported motor model and operating mode.
| Control basis | Supported decision |
|---|---|
| Equal frequency references | Does not by itself control torque sharing. |
| Current or electrical power | Useful for monitoring, but the evidence does not establish either as an accurate torque-sharing variable. |
| Estimated electromagnetic torque | Preferred feedback variable when a vector-control drive can calculate and expose it. |
| Shaft-position feedback | Required by the proposed frequency-based synchronization method to account for slip; the evidence specifically identifies absolute encoders. |
PChV2 Interface Limitation
The stated PChV2 limitation is the absence of an analog torque output. Therefore, a direct analog connection that sends the master's calculated torque to the follower cannot be implemented as described.
The evidence does not identify a PChV2 parameter, communication object, firmware capability, or alternate output carrying estimated torque. Before selecting an external controller, verify from the applicable PChV2 documentation whether torque is available through any documented interface. If it is not available, the proposed torque master-follower architecture cannot be completed with these drives alone.
Engineering Decision Path
- Confirm the motor ratings, gearbox arrangement, and whether the motors have equal or different power ratings. Do not command equal absolute torque when that would overload the smaller motor.
- Determine whether each drive supports vector control with a calculated torque value and whether PChV2 exposes that value to another controller or drive.
- If usable torque data is available, regulate speed with the master and use the master's torque value as the follower load reference, with a PID-based correction strategy.
- If torque data is unavailable, do not substitute identical frequency references and assume balanced loading. Select a drive or control architecture that exposes the required feedback, or redesign the synchronization method around measured shaft feedback.
- Define the method for bringing the follower online under load. The evidence supplies no supported transfer sequence, timing, or thresholds, so these values must come from the drive documentation and mechanical risk assessment.
Commissioning and Verification
Commission at controlled load and trend each motor's torque estimate, current, power, speed reference, and operating direction where those signals are available. Increase shaft load while confirming that both motors contribute positive driving torque and remain within their individual ratings.
Reject the setup if one motor persistently drives the other, either drive enters regenerative operation unexpectedly, or the gearbox shows abnormal loading. Also verify that the mechanical torque path actually permits the intended sharing; control cannot correct unequal gearbox loading caused by mechanical condition or geometry.
No evidence-supported sharing tolerance, engagement threshold, PID gain, or switching delay is available. Establish acceptance limits from the motor, drive, gearbox, and machine requirements rather than inserting an assumed value.
FAQ
Can two PChV2 drives run two motors on one shaft?
The mechanical arrangement is possible, but equal frequency commands do not guarantee balanced torque. A validated master-speed and follower-torque strategy requires an accessible torque signal.
Does PChV2 provide an analog torque output for a follower drive?
The supplied evidence states that PChV2 has no analog torque output. Verify whether the applicable documentation exposes torque through another interface before committing to the architecture.
Can motor current or power replace torque feedback?
Not as a proven equivalent in this application. Current and electrical power can support diagnostics, but motor losses, parameter differences, and slip prevent assuming that they provide accurate electromagnetic torque sharing.
