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Qian, K X1; Wan, F K1; Ru, W M1; Yuan, H Y1; Zeng, P1

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Based on the development of the permanent maglev impeller TAH and permanent maglev axially driven impeller pump, a permanent maglev impeller LVAD has been developed. The permanent maglev needs no rotor position detection and feedback control, nevertheless the eccentric distance (ED) and vibration amplitude (VA) of the levitator have been measured to demonstrate the levitation and to investigate the factors affecting levitation. The device is a centrifugal type impeller pump, which has a rotor and a stator. The rotor is driven radially and levitated by passive magnetic bearings. The rotor position is detected by the use of 4 Hall sensors distributed evenly on the stator against the passive magnetic rings in the rotor. The voltage difference of sensors is converted into ED and VA. Results indicated that the rotating speed (RPM) and pump flow rate (Q) as well as the air-gap have great influence on ED. If the RPM is lower than 3250 or Q is smaller than 1 l/min, the maximal ED will reach the value of the air-gap, indicating that the rotor is not completely disaffiliated from the stator and thus is unsuspended. Along with the increase of RPM and Q, the ED will decrease quickly. For example, at 4000- 4750 RPM, the maximal ED is round 0.08 mm at 4-10 1/min of Q (air-gap: 0.15 mm); and VA is about 0.06 mm. If the air-gap is enlarged to 0.20 mm, ED will increase to 0.12 mm, but VA remains unchanged. Fortunately, the maximal ED will reduce to 0.05 mm and VA will reduce to 0.03 mm when the fluid changes from saline to blood. The pressure pumped has no effect on the passive levitator.

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