86 Frequency Converters and Motors 3.3 Automatic Motor Adaptation (AMA) Motor data on the motor nameplate or from the motor manufacturer’s datasheet are given for a specifi c range of motors, or a specifi c 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. Also as seen above there are several compensations which require setting. For modern FC’s, fi ne-tuning to the actual motor and installation can be a complicated and troublesome task.
In order to make installation and initial commissioning easier, automatic confi guration functions like the Automatic Motor Adaption (AMA) from Danfoss are becoming increasingly common. These functions measure for example the stator resistance and inductance. The eff ect of the cable length between FC and motor is also taken into account. The parameters required for diff erent motor types diff er in important details. For instance, the back EMF value is essential for PM motors and saturation point level is important for SynRM motors. Therefore diff erent types of AMA are required. Note that not all FC’s support the AMA function for all motor types. In principle two types of AMA are used:
Dynamic The function accelerates the motor to a certain speed to perform the measurements. Typically the motor must be disconnected from the load /machine for “identifi cation run”. Static The motor is measured at 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 infl uences during measurement.