This paper presents a sliding mode controller for a wound rotor synchronous machine, acting as a generator for an isolated load. The standard dq-model of the machine is connected to a resistive load. A sliding surface is defined in order to fulfill control objectives, and the Ideal Sliding Dynamics is proved to be stable. From the desired surface, the standard sliding methodology is applied, and a robust controller is obtained. Numerical simulations are also presented to validate the control law.