The noncontact rotary pumps under development for use as artificial heart pumps are highly efficient and can prevent thrombus formation. In these pumps magnetic bearings have been widely used to support the rotors to avoid any physical contact. The use of magnetic bearings, however, has led to requirements for the control of a large degree of freedom and for a separate driving motor. This paper introduces 2 types of levitated motors, each of which uses a combination of a rotary motor and a magnetic bearing. These motors are suitable for use in artificial blood pumps because they are small in size and can replace contact components. The radial type levitated motor has the merit of being small in size and capable of controlling the 2 degrees of freedom in the x and y directions. The axial type motor controls only one degree of freedom in the z direction. This paper also introduces the theoretical background of the functions of the motor and magnetic bearing. Experimental results of tests of the proposed motor show a great potential for its application in rotary blood pumps.
General solution of levitation control applicable to PM synchronous and induction type rotating motor is presented. It is intended for a single rotor to have both functions of magnetic bearing and rotating motor. The rotational control is achieved with the traditional P pole magnetic flux, while the radial force is controlled with either P+2 or P−2 pole magnetic flux in the stator. In the previous work, the proposed general theory of levitated motor is successfully confirmed with no load experiments.
In this paper, the load capability of the levitated motor is tested using a horizontal type experimental setup. The stator has 8 concentrated wound electromagnets, each of which is controlled individually by a DSP and power amplifier. The radial load is the gravity of the rotor, while the produced rotating torque is measured with a noncontact variable torque load system. The results obtained are discussed in detail.
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