Question:
Can low-performance positioning applications also be solved with the Sensorless V/f motor control mode, i.e. with asynchronous motors without encoders?
Answer:
Yes, the setpoint generation in the FAST Motion profile generator is completely independent of the motor control mode in the axis.
The motor is controlled with a setpoint frequency that exactly matches the setpoint speed from the profile generator.
With a boost function (additional voltage or minimum current), torques can also be pre-controlled at setpoint frequency = 0 Hz.
In principle, however, a control deviation remains in such an open control loop without I-component.
This means that tracking errors cannot be compensated to zero and a drift-free standstill cannot be reliably achieved.
In an exemplary test setup without load, as sketched below, the permanent control deviation (tracking error) was always well below 0.5 mm on the load side of the geared motor.
This result was achieved with Deafult adjustment when selecting the Lenze motor from the catalogue, i.e. without individual adjustment of the control parameters.
This technology is used in variable speed drives, metering applications, mixing drives, bearing technology, conveying drives, etc.
Here, individual axes with asynchronous motors can be used cost-effectively without encoders, even if the overall system is actually designed with i700/i950 servo inverters.
