PROTOTYPE CONTINUOUS-FLOW VENTRICULAR ASSIST DEVICE SUPPORTED ON MAGNETIC BEARINGS

This article describes a prototype continuous flow pump (CFVAD2) fully supported in magnetic bearings. The pump performance was measured in a simulated adult human circulation system. The pump delivered 6 L/min of flow at 100 mm Hg of differential pressure head operating at 2,400 rpm in water. The pump is totally supported in 4 magnetic bearings: 2 radial and 2 thrust. Magnetic bearings offer the advantages of no req uired lubrication and large operating clearances. The geometry and oth er properties of the bearings are described. Bearing parameters such a s load capacity and current gains are discussed. Bearing coil currents were measured during operation in air and water. The rotor was operat ed in various orientations to determine the actuator current gains. Th ese values were then used to estimate the radial and thrust forces act ing on the rotor in both air and water. Much lower levels of force wer e found than were expected, allowing for a very significant reduction in the size of the next prototype. Hemolysis levels were measured in t he prototype pump and found not to indicate damage to the blood cells.