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Développement du convertisseur destiné à l'entraînement de machine à aimants permanents

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The IEC norm 60034-30 defines new international standards for efficiency of electric motors. IE1 is standard efficiency, IE2 is high efficiency, and IE3/IE4 are the premium class. Circle Motor AG assumes that the premium class efficiency factor for motors with power less than 22kW is easier to achieve with Permanent-Magnet-Motors enhanced by electric inverters than with asynchronous motors. The goal of this work is to achieve an overall “efficiency factor” of 90% through a high-efficiency 3kW-rated input Permanent-Magnet-Motor enhanced with an electric inverter, and then to perform measurements on the pump drive.

The “efficiency factor” measurement results showed worse performance than expected for both the inverter and the motor. One reason is due to high iron losses in the motor that are produced by high frequency currents of inverter. Another reason is the relatively high ohmic resistance of the copper motor winding caused by the chosen coil production method.

By filtering high frequency currents at the rated power, the motor efficiency factor reaches up to 89.5%, which complies with premium class IE3. In generator mode the efficiency reaches 92.8%.

We note that the positive result of this work is that the inverter can be produced with very low standby power losses - in our current work with 160 mW.

It is necessary to admit that every detail can be responsible for success or failure during research and development activities of premium class motors. The optimization activities mainly belong to the area of additional losses of electric machines. In this report we have encountered all research results on the theme of Additional Losses that resulted from the current research work.

The concept of drive control from the previous research project has shown itself as efficiency aware. The total efficiency factor of 90% can be reached by a system coupling a drive controller with a synchronous motor and the “know how” from this work. The total efficiency of motor and inverter is in the range of asynchronous motors belonging to the IE2 efficiency class with a frequency converter. This is why energy measurements such as pump application have been excluded.