With the Alspa GD3000E drive from Cegelec, it is not a problem, because if the drive detects the loss of the encoder signal, it automatically switches to encoderless vector control. The seamless transfer is achieved with no transient in either speed or torque. And the drive can issue an alert that remedial action is required.
Many of today’s inverters provide operation either with an encoder, or in encoderless vector control mode. But what happens if you’re running with encoder feedback, and then lose the feedback signal?