In order to improve the dynamic characteristics of 3-phase AC induction motors, the squirrel cage rotor for the high speed built-in type motor spindle system was designed and manufactured with powder contained epoxy composite material and aluminum squirrel cage. The Young’s modulus, coefficient of thermal expansion, resistivity and magnetic permeability of the Mn-Zn ferrite powder contained epoxy and the iron powder contained epoxy were measured with respect to powder volume fraction to determine the optimum powder volume fraction. Then the powder contained epoxy composite rotor was manufactured by embedding the aluminum squirrel cage into the composite. The dynamic and electrical performances of the AC induction motor equipped with the developed composite rotor were measured and compared with those of a conventional AC induction motor.
Since the critical whirling vibration frequency of high speed built-in type motor spindle systems is dependent on the rotor mass of the built-in motor and the spindle specific bending modulus, the rotor and the shaft were manufactured using magnetic powder contained epoxy and high modulus carbon fiber epoxy composite, respectively. In order to enhance the magnetic flux of the composite squirrel cage rotor of an AC induction motor, a steel core was inserted into the composite rotor. The motor parameters of the developed composite rotor system were obtained from the no-load and blocked rotor tests and the effect of thickness of the steel core on the motor performance was investigated. From the magnetic analysis, the optimal steel core size for the dynamic characteristics of the rotor system mounted on the carbon fiber epoxy composite spindle was determined. Because of high temperature and frequency environment of squirrel cage rotor, thermal and frequency characteristics of rotor material must be verified to predict behavior of the rotor. In order to find out temperature and frequency effect of composite squirrel cage rotor on motor performance, various experiments were performed using TMA tester, DMA tester and permeameter and so on. This paper also provide the optimal configuration of composite squirrel cage rotor with respect to the geometric shape of rotor component such as conductor bars and steel core.
If the spindle shaft of an air spindle system is made of high stiffness carbon fiber composite material, the spindle system will be dynamically robust because the maximum rotating speed of a spindle (or rotor) system is usually restricted by the critical whirling vibration frequency of spindle shaft which is proportional to (EI/m)0.5 (E : Young’s modulus, I : flexural stiffness of shaft section, and m : mass of spindle per unit length). In this paper, the composite air spindle system composed of a high modulus carbon fiber composite shaft, powder contained epoxy composite squirrel cage rotor and aluminum tool holder was also introduced. For the optimal design of the composite air spindle system, the stacking sequence and thickness of the composite shaft were selected considering the fundamental natural frequency and deformation of the system. Then the dynamic characteristics of the composite spindle system were compared with those of a conventional steel air spindle system.