The levitation of bulk Y-Ba-Cu-O superconductors can be controlled using a Bi-Sr-Ca-Cu-O (Bi2223) superconducting electromagnet. It was found that stable levitation without tilting could be obtained only when the sample trapped a certain amount of fields, the minimum of which depended on the external field and sample dimensions. We employed a novel analysis method for levitation based on the total energy balance, which is much simpler than the force method and could be applied to understanding general levitation behavior. Numerical analyses thus developed showed that stable levitation of superconductors with large dimensions can only be achieved when the induced currents can flow with three-dimensional freedom.