Magnetic levitation technology, which can support an impeller without contact, is applied for durability and lifetime enhancement of an artificial heart. We have developed an artificial heart using a radial type self-bearing motor. The plus minus two-pole algorithm is adopted to levitate and rotate the rotor. Radial position of the rotor is controlled actively, and axial position of it is passively stable within the thin rotor structure. In this paper, new estimating equations of magnetic suspension characteristics were proposed in order to reduce the designing time and improve the calculation accuracy. Estimating equation of the magnetic suspension force which added the circumferential component of electromagnetic force and introduced square wave flux density distribution was developed. The estimating equation of the negative spring force was also developed. Calculation accuracy of the magnetic suspension force was improved by using the estimating equation of that. The estimating equations have the sufficient calculation accuracy that can be used for the design.
