Evidence to watch
The function is proved by changed behavior, not by a parameter value alone.
- Actual speed under load
- Output current and estimated torque
- Motor-model or identification status
F-21 · vendor-neutral function
V/Hz vs Sensorless Vector VFD Control
V/Hz control applies a frequency-to-voltage profile and is simple and robust. Sensorless vector control uses a motor model to regulate flux and torque more accurately, especially at low speed and changing load.
Why it matters
The behavior behind the parameter.
The control mode affects low-speed torque, speed regulation, motor-data requirements and commissioning effort. It is separate from local, terminal or fieldbus command source.
- V/Hz is scalar control; sensorless vector estimates motor state.
- Vector performance depends on correct nameplate data and often motor identification.
- Neither mode turns a standard drive into a servo positioning axis.
Interactive proof
Test v/hz vs sensorless vector vfd control in three passes.
Keep the motor, load and starting condition constant. Change one function at a time, then use the electrical and mechanical evidence to explain the result.
- 01
Run both modes above 25 Hz with the same steady load.
- 02
Reduce frequency below 10 Hz and increase load while comparing torque and speed error.
- 03
Correct the nameplate and repeat motor identification before judging vector performance.
Common commissioning mistakes
These errors can make a healthy drive appear faulty or create a misleading test.
- Calling keypad/terminal selection a motor control mode.
- Expecting vector control to compensate for wrong motor data.
- Operating a self-cooled motor slowly at high torque without thermal review.
Primary technical references
Transfer the concept; verify the exact drive.
This guide uses vendor-neutral terminology. For real equipment, use the manual for the installed model, option cards and firmware, plus the machine risk assessment and approved commissioning procedure.
Related VFD functions
F-41
VFD Current Limit and Stall Protection
Current limiting caps drive output current and therefore available motor torque. The drive may slow or extend acceleration instead of immediately tripping when the load demand reaches that limit.
Read and test F-23VFD Speed Reference Sources
The speed reference is the requested output frequency or process demand. It can come from the keypad, 0–10 V, 4–20 mA, preset speeds, a motorized potentiometer, PID output or a fieldbus word.
Read and test F-71–F-72VFD PID Control for Pumps and Fans
A drive PID function compares a process setpoint with transmitter feedback and continuously changes motor frequency to reduce the error.
Read and testFrom explanation to evidence