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 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 – free download here
Functions like AMA that automatically tune a VSD to the connected motor are not only useful to make installation and initial commissioning easier. If a VSD is configured optimally for the actual motor connected and for the characteristics of the cable between the VSD and motor, it helps to also optimize the total efficiency of the VSD and motor combined. If a motor is magnetized correctly, it operates more efficiently. If a VSD is tuned to the connected motor correctly, magnetization of the motor can be optimal. Therefore if energy efficiency and lower operating costs are important, doing an AMA during commissioning can help. Although the improvement may not be very significant, it definitely does help and if you want to save operating costs, every little helps.
When you have desided for a VLT (Danfoss) please check your cabellength 20m, 50m or 150m. And motor types especially
Thanks for your reaction Jens,
With one and the same Danfoss VLT frequency converter you are able to control the traditional asynchronous or inductance motor (IM), high-efficiency permanent magnet (PM) motors, and synchronous reluctance (SynRM) motors. The type of motor controlled has no effect on the length of the cable to the motor; up to 150/300 mtr (screened/unscreened).
More info here: http://vlt-drives.danfoss.com/Themes/Motor-Independence/