| The synchronous reluctance permanent magnet (SR-PM) motor is a novel combination of the synchronous reluctance motor and the synchronous magnet motor. The SR-PM motor has both the characteristics of the synchronous reluctance motor and the synchronous magnet motor, which presents a bran-new motor design and operating conception. Because a SR-PM motor has many good features, such as high power density, a wide constant-power speed range, excellent efficiency, small size, light weight and so on, it has been a focus in the application field of adjustable speed drives.The plastic adhibiting NdFeB permanent magnet which has comparatively low magnet performance, but has comparatively lower cost and excellent Manufacturing performance are inserted into the permanent magnet slots of the 4-pole SR-PM motor. As the relative magnetic conductivity of the permanent magnet corresponds to that of the air, the d- axis reluctance is much higher than the q-aixs reluctance, the d-aixs synchronous inductance is much lower than the q-axis synchronous inductance, the higher saliency ratio Lq/Ld and greater reluctance torque can be reached; at the same time, permanent magnet field excitated by permanent magnet in the d-axis is weaker than that of common Permanent Magnet synchronous motor, so the power factor and efficiency can be greatly increased and reluctance torque can be sufficiently utilized by unit current maximum torque control method in speed adjusting with field weakening. As the q-axis inductance is comparatively very high, armature reaction flux linkage is adjusted to regulate air-gap compound magnetic field of the motor in order to keep voltage balance and to realize wide constant-power speed adjusting with field weakening range.Based on the brief introduction of the structural characteristics of the SR-PM motor and the finite-element numerical computing methods of the electromagnetic field, two dimensions finite-element techniques are used to analyze the magnetic field and the performance of the motor. Based on the results of no-loading and loading electromagnetic analysis, the effects of permanent magnet thickness, magnet material attribute and air-gap length on the permanent magnet flux linkages and electrical torque are concluded, then the q-and d-axis synchronous inductance and salience ratio are evaluated by means of flux linkages increment, at last the effects of magnetic circuit saturated characteristic on the motor parameters are concluded. The results would be used in optimizing rotor dimension design of the SR-PM motor. |
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