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1、1Introduction The vector control, also known as the field-oriented control (FOC), of a permanent magnet synchronous motor (PMSM) is the algorithm often used in todays advanced motor control drives. Such advanced motor control algorithms require the setting of motor electrical parameters for its prop
2、er functionality. This application note deals with the measurement of electrical parameters needed for vector control of PMSM. The electrical parameters are needed to set the current PI controller gains to get the desired closed-loop performance and for BEMF observer constants. The proposed measurem
3、ent techniques determine a number of pole pairs, a stator resistance, synchronous inductances, and an electrical constant with common measurement equipment. A summary of PMSM sensorless control and explanation of motor control terms can be found in 1 . 2Motor parameters needed for PMSM FOC One of th
4、e possible methods to set the PI controller gains, is to calculate them from motor parameters. The current PI controller gains in time domain are calculated from the motor electrical parameters 1 ; see the following equations. Freescale Semiconductor Document Number:AN4680 Application Note Rev. 0, 0
5、2/2013 PMSM Electrical Parameters Measurement by:Viktor Bobek 2013 Freescale Semiconductor, Inc. Contents 1Introduction1 2Motor parameters needed for PMSM FOC.1 3Motor pole pairs3 3.1Background.3 3.2Guide.3 4Stator resistance.5 4.1Background.5 4.2Guide.5 5Synchronous inductances7 5.1Background.7 5.2
6、Guide.11 6Back-EMF constant12 6.1Background.12 6.2Guide.13 7Conclusion.14 8References.14 9Acronyms and Abbreviated Terms.15 Equation 1 Equation 2 Where 0 is the natural frequency of the current closed-loop system (loop bandwidth) and is the current loop attenuation. Therefore, the PMSM vector contro
7、l algorithm typically requires the following parameters. Table 1. Electrical parameters needed for FOC Electrical parameters needed for FOC current PI controller gains calculation ParameterDimensionDescriptionUsed in constant calculation Rs()Resistance one of the motor phase Current PI controller BE
8、MF Observer Ld(H)d-axis inductance of one motor phase Current PI controller BEMF Observer Lq(H)q-axis inductance of one motor phase Current PI controller BEMF Observer Additional electrical parameters needed for FOC Ke(V.s/rad)Electrical constantBEMF Observer pp(-)Motor pole pairsSpeed and position
9、mechanical/electrical quantities recalculation The speed PI controller gains in time domain are calculated from the motor/load mechanical parameters; see Equation 1 on page 1 and Equation 2 on page 2 Equation 3 Equation 4 Where 0 is the natural frequency of the speed closed-loop system (loop bandwid
10、th) and is the speed loop attenuation. Therefore, the PMSM vector control algorithm typically requires the following parameters. Table 2. Mechanical/load parameters needed for FOC speed PI controller gains calculation ParametersDimensionDescriptionUsed in constant calculation J(kg.m2)Total mechanica
11、l inertiaSpeed PI controller Bm(N.m.s)Viscous friction coefficientMore precise speed PI controller gains setting The measurement of individual electrical parameters is described in the following chapters of this application note. Motor parameters needed for PMSM FOC PMSM Electrical Parameters Measur
12、ement, Rev. 0, 02/2013 2Freescale Semiconductor, Inc. Motor pole pairs 3.1Background The motor pole pairs parameter defines a ratio between mechanical and electrical quantities (mechanical vs electrical rotor position/speed). The motor pole pairs represent the number of north and south segments the
13、rotor contains. 3.2Guide The equipment required to measure motor pole pairs depend on the method used for measurement. DC power supply Three-phase inverter, oscilloscope, hand velocity meter, and a current probe Driving motor, oscilloscope and a voltage probe Usually, the number of the motor pole pa
14、irs is written on the label of the motor. If there is no information regarding the number of pole pairs, it can be determined. See the following subsections. 3.2.1Method to determine low number of the pole pairs Guide: The following steps describe the method to determine the low number of motor pole
15、 pairs. See Figure 1. 1. Connect the phase A wire to the positive potential (+) and phase B and C to negative potential (-) of the voltage source. 2. Set a current limit of the power supply to such a level so that the user is able to rotate the shaft manually, and the rotor is aligned in the stable
16、position. Common current limit is about 10% of the rated motor current. For more powerful motor, the current limit is lower. 3. Draw a line/sign for every stable position in which the rotor is aligned. 4. Number of stable positions is equal to the motor pole pairs. 3 Motor pole pairs PMSM Electrical Parameters Measurement, Rev. 0, 02/2013 Freescale Semiconductor, Inc.3 Figure 1. Method for the determination of low number of pole pairs 3.2.2Method to determine high number of
