Motor data on the motor nameplate or from the motor manufacturer’s datasheet are given for a specific range of motors, or a specific design, but rarely do those values refer to the individual motor. Due to variations in the production of motors and the installation, those motor data are not always accurate enough to ensure optimal operation.
But there are several other compensations which require setting. For modern frequency converters, fine-tuning to the actual motor and installation can therefore be a complicated and troublesome task.
In order to make installation and initial commissioning easier, automatic configuration functions like the Automatic Motor Adaption (AMA) from Danfoss are becoming increasingly common. These functions measure for example the stator resistance and inductance. The effect of the cable length between the frequency converter and the motor is also taken into account.
The parameters required for different motor types differ in important details. For instance, the back EMF value is essential for PM motors and saturation point level is important for SynRM motors. Therefore different types of Automatic Motor Adaptation (AMA) are required. Note that not all frequency converters support the AMA function for all motor types.
In principle, two types of AMA are used:
The function accelerates the motor to a certain speed to perform the measurements. Typically the motor must be disconnected from the load /machine for “identification run”.
The motor is measured at a standstill. This means there is no requirement to disconnect the motor shaft from the machine. It is important, however, that the motor shaft is not rotated by external influences during measurement.
From Danfoss’ Facts Worth Knowing About Frequency Converters