Based on the coordinate transformation theory and principle of electromechanical energy conversion, it is demonstrated that the rotor field-oriented control decouples not only flux and torque but also transformer electromotive force (TEMF) and motion electromotive force (MEMF). The field-oriented control of induction motor can be achieved by control of rotor motion electromotive force. A universal voltage vector controller for induction motor, based on control of motional electromotive force, is proposed. The universal controller can realize rotor flux orientation, air-gap flux orientation, stator flux orientation and even arbitrary flux orientation. Moreover, it can be used not only in constant torque control with constant field but also in constant power control with weakening field. The results of simulation are presented and show that the proposed control system has high dynamic performance.