Open AccessThis paper investigates the torque ripples of disk-type low-power brushless direct current motor (BDCM) with permanent magnets. In spite of numerous studies on designing of valve engines this issue is understudied as yet. The torque ripples cause noise and vibration and can significantly limit accuracy when used in instrumentation, computer technology.
We consider a motor that includes a power unit consisting of a rotor and a stator. There are ferrite elements of sensor on the rotor, and the nonmagnetic disk, bonded to it, contains permanent magnets. The rotor is mounted on a rotating shaft. The stator consists of a steel casing and bonded to it non-magnetic, non-conductive disk with holes. In the disk holes from both sides are mounted armature coils. The armature winding consists of two sections each of which has 6 coils. Each adjacent coil in section has an opposite direction of winding. The coils are arranged circumferentially and are shifted relative to each other; the displacement angle between the coils of one section is equal to 2π/6 (rad). Sections are also shifted relative to each other; the angular shift is π/6 (rad). Sections are connected to the output terminals of the electronic switch. Sections of motor windings have the reverse full-wave power.
The paper has investigated the steady operation at four-stroke switching and under constant load (torque). In this case, the electromagnetic torque and rotor speed are periodical functions of the rotor rotation angle. The dependencies of the averaged torque on the rotation speed have been obtained. The spectral distribution of the torque ripples at various rotor speeds of rotation has been calculated. The dependencies of the torque on the speed were studied both at constant speed and taking into account the uneven speed. Based on the research findings of disk type BDCM was computed a level of ripples amounted to 0.8 - 5%, which is quite acceptable for use in a drive. The results are useful for selecting the motor parameters at its designing stage.