What is a rotor?
A rotor is a rotating body supported by a bearing. The disc itself does not have a rotating axis of the object, when it adopts rigid connection or additional axis, can be regarded as a rotor.
The rotating part of a motor or certain rotating machines, such as turbines. The rotor of the motor is generally composed of an iron core with a coil, a slip ring and a blade.
Electric motors, generators, gas turbines and turbine compressors are the main components of high speed rotation in power machinery or working machinery.
When the main rotor rotates at high speed, its speed approaches the critical speed. Even mechanical failure due to resonance. The natural frequency of transverse vibration of rotor is multi-order, so its corresponding critical speed is also multi-order. When the working speed of the rotor is lower than the first order critical speed, it is called rigid rotor, and when the working speed of the rotor is higher than the first order critical speed, it is called flexible rotor.
The operating speed of any type of rotor must not be close to the critical speed. The critical speed of rotor depends on its manufacturing material, structural form, geometric size, bearing characteristics and other factors.
For example, in an induction motor, a rotor consisting of a rotating shaft core and a closed conductor embedded in the core produces a high-speed rotational motion driven by a rotating magnetic field generated by the stator windings. Both ends of the rotor adopt rolling bearings and are mounted and fixed in the end cover of the motor housing.
Because no matter what type of rotor, when its operation will produce centrifugal inertia force, and affect the strength and mechanical efficiency of the rotor. Therefore, the rotor is properly balanced and the mass of each part is redistributed in order to reduce the centrifugal inertia force generated in the process of rotation.
When the unbalanced mass of the rotor is approximately distributed on the same plane perpendicular to the axis of rotation, such as the balance of a single disc CAM, static balance can be achieved by increasing or removing the size and position of the weight of the balance block, even if the center of mass of each part of the rotor and the axis of rotation coincide.
When the unbalance weight of the rotor is located in the parallel plane of the vertical axis of rotation, only after the rotor rotates up, there will be unbalance weight, the elimination of this dynamic unbalance, more by changing the weight and position of the balance block, eliminate the inertia force and inertia force couple to achieve dynamic balance. Avoid rotor vibration on the elastic support.