1. Material and selected material characteristics The motor shaft and shaft extension key are usually 45 steel, and the allowable stress under normal temperature, static load and general working conditions is 186MPa. The rotor and stator of Haocheng Motor’s wound three-phase asynchronous motor are also equipped with three-phase windings and are connected to external varistors through slip rings and brushes.
Adjusting the varistor resistance can improve the starting performance of the motor and adjust the speed of the motor.
2. Safety factor
The safety factor depends on many factors. If the safety factor is too large, the material will be wasted; if the safety factor is too small, the components may be unsafe. Generally, the following aspects should be considered:
(1) The accuracy of the load estimation;
(2) The simplification process and the accuracy of the calculation method;
(3) The uniformity of the material;
(4) the importance of construction;
(5) Working conditions of parts, reducing self-weight and other factors. The general component values are: 1.5-2.0 for plastic materials according to the yield limit; 2.0-5.0 for brittle materials according to the strength limit. The above allowable stress is 186MPa, indicating that the safety factor is 353/186=1.9.
3. Determination of allowable stress
Shaft and shaft extension key are 45 steel, allowable stress (tension and compression) [σ]=186MPa. Allowable shear stress [τ]=(0.6～0.8)×[σ]=112MPa, and allowable extrusion stress [σjy]=(1.7～2.0)×[σ]=316MPa.
4. Strength check calculation steps
(1) Motor rated data: power (referring to the amount of work done by the object in unit time) P, speed n, service factor SF.
(2) The shaft extension and shaft extension key parameters are: shaft diameter d, key width b, key height h, key length l.
(3) Shaft cross-sectional area F=πd2/4.
(4) Torque M=P×SF/Ω, where Ω=2πn/60. YE3 three-phase asynchronous motor Compared with single-phase asynchronous motor, three-phase asynchronous motor has better running performance and can save various materials. According to the different rotor structures, three-phase asynchronous motors can be divided into two types: cage type and wound type.
(5) The torsional section coefficient of the shaft is W=πd3/16.
(6) Axial tensile strength condition: τ=M/W <= [τ]
Strength conditions of shaft extension keyway and shaft extension key: σjy =2M/d/Fjy<=[σjy], where Fjy =l×h/2.
Post time: 2022-02-21