Current sensors for shaft-sensorless control of inverter fed induction machines - Industrially used sensors vs. new current derivative sensors

The emerging technology of shaft-sensorless control has been developed through the past decade. Some big improvements have been made on the evaluation of position information out of so-called non-model based methods, which do not have the drawback of the classically mathematical models. However, the improvement in the field of the current sensors was not focused on this particular topic and thus has not brought that much enhancement for mechanical sensorless control With the introduction of the current derivative sensor (CDI) a new concept specialized for sensorless control has been exploited. The quality of the control signals can be increased and the drawbacks with the measurement sequences needed for the detection cycles are reduced with the help of cheap, easy to use, and simple to fabricate derivative current sensors.