This paper presents the modeling and design of a three-dimensional (3-D) Helmholtz coil system for wireless control of magnetically actuated robots. Instead of using moving permanent magnets to generate the external magnetic field needed for magnetic actuation, driving a set of stationary Helmholtz coils with power electronics offers enhanced control flexibility and precision through active feedback. A modular drive is developed to operate the custom pulsed 15 kW 60 mT 3-D Helmholtz coil setup. A method for modeling the generated magnetic field is developed to enable the precise motion control of untethered robots. The prototype system is verified by precisely actuating a magnetized cubic robot.