Getting the Back-Emf Voltage Constant of Permanent Magnet Motors with Just One Twist of the Wrist using Gen3i Data Recorder
The parameter identification of permanent magnet motors is needed when a new motor prototype must be quickly analyzed. The parameter identification can be performed with complicated tests using inverter and a driving machine, or using simpler methods that do not need any inverter supply and prime movers. This paper focuses on a fast identification of the motor back-emf voltage constant using the HBM Gen3i data recorder. The motor is rotated by hand with just one twist of the wrist and the method is able to get very good results even for non-sinusoidal motors.
Due to their high torque density and higher efficiency with respect to other motor types, Permanent Magnet (PM) motors are able to create energy savings in a number of applications. The advancement of Adjustable Speed Drives (ASD) has caused PM motors to have expansion in many fields. Some of these fields include: traction, automotive, renewable power generation, electrical mobility, compressors electric aircraft and home appliances . Different PM machine designs are adopted to fulfil the application requirements. The rotor design determines the topology of the PM machine. The most common PM machines are Surface Mount (SM) PM machines, Interior Permanent Magnet (IPM) machines (single layer and multilayer rotors), inset PM machines, flux-concentrating PM machines and so on.
The application engineers who must implement specific motor control strategies need parameter identification procedures to get the motor parameters. The motor parameters that are usually used in motor control are: stator resistance, stator inductances and the magnets flux linkage (or the back-emf constant). The stator resistance and inductance can be obtained very quickly with line-to-line impedance measurement for different rotor positions or through a short-circuit test. The magnets flux is usually obtained by means of a no-load test (hereinafter called as conventional method); the Motor Under Test (MUT) is rotated by a Driving Motor (DM). The magnets flux is calculated from the induced voltage at the machine terminals and the electrical speed.
This paper proposes a very simple method for the identification of the PM motors magnets flux using the HBM Gen3i data recorder. Respect to the conventional method, the proposed method does not need a DM and it can be applied to PM motors having non-sinusoidal back-emf voltages. The paper is organized as follows. First, the conventional method is described in Section II. Then, the proposed method is analyzed in Section III. Section IV concludes the paper.