C-120 Parameter Reference
AC30 series Variable Speed Drive
Functional Description
The Switchover Enable parameter (1701) provides the user with the option to automatically, and as seamlessly as possible, continue operating in
sensorless mode in case of an encoder failure. The MRAS estimator tracks the speed of the motor even if the drive uses encoder as its primary
feedback for control. If the discrepancy between the speed measured by encoder and the estimated speed is greater than 300 RPM it is assumed
that the encoder has malfunctioned and the control will automatically be transferred to use estimated speed as its feedback signal. The drive will
continue to work in sensorless mode until the next stop cycle. There will be no attempt to ‘reconnect’ encoder on the fly even if its signal recovers.
Upon the move to sensorless operation a warning will be issued that this has taken place.
The switchover will not be performed, even if enabled, during autotune sequence, if the flycathcing is enabled, until the estimator converges to
correct speed (typically within first 50-100ms after starting the drive), and until the motor has accelerated to 95% of its initial speed setpoint. The
switchover will also not be performed if the setpoint speed is lower than the switchover threshold of 300 RPM.
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