<h3>Purpose</h3> Development of pediatric left ventricular assist devices (LVADs) has severely lagged behind that of adult LVADs, primarily due to the size and hemocompatibility constraints of pediatric anatomy. To quantify sources of blood trauma within a device, we proposed a hemocompatibility assessment platform (HAP) that can evaluate the hemocompatibility of individual components of LVADs. To eliminate the hemolysis induced by the HAP itself, we incorporated passive magnetic bearings to suspend the rotor radially and an active magnetic bearing (AMB) to control the axial position. In this study, we evaluated AMB forces of 2 geometries and validated the model by comparing its predictions with experimental results. <h3>Methods</h3> The AMB comprises a stator with an electromagnetic coil and a rotor with a permanent magnet (PM) ring (1 mm and 2 mm thickness). The AMB numerical model was established in COMSOL 5.5 using the finite-element method. The magnetic forces generated by the AMB were evaluated by increasing the rotor-stator gap from 0.1 mm to 0.5 mm with a 0.1 mm increment and by varying the coil current from -2 A to 2 A with a 1 A increment. AMB force data was collected experimentally by a precision force transducer on an XYZ-micrometer-driven stage. <h3>Results</h3> The average error of the numerical models was 8.8% and 7.0% for 1 mm and 2 mm thick PM rings, respectively. Higher errors were seen at small (<0.2 mm) rotor-stator gaps. The change in magnetic force due to electrical current, or magnetic stiffness, is greater in the thicker PM ring. For both PM ring sizes, the AMB exhibits high magnetic stiffness from -1 A to 1 A, though it saturates for currents of -2 A and 2 A. This region of high current stiffness was identified as the optimal control region. <h3>Conclusion</h3> AMB force generation was characterized as a function of current and gap, both experimentally and numerically. In future work, this function will be used to tune a control algorithm to modulate current supplied to the AMB, ultimately stabilizing the rotor axially. Additionally, if design specifications such as PM ring thickness or material change, the numerical model can be used to quickly generate a new function for the AMB control algorithm.