The paper examines the optimal efficiency excitation of a variable-reluctance motor (VRM) drive operating at constant speed. The drive comprises a motor, an inverter, an excitation and a control strategy. The excitation refers to a prescribed relationship between the phase currents and rotor position that results in the desired drive behaviour. The excitation is considered from an integrated viewpoint such that overall drive efficiency is maximised for a given torque and speed. An algorithm for the determination of optimal excitation is presented. The algorithm is based on the determination of excitation that nominally meets the drive torque-speed requirement, followed by optimisation of this excitation to improve efficiency. Other performance criteria, such as torque ripple or acoustic noise, could be considered in a similar manner, with appropriate models. The paper applies the algorithm to high-power (60 kW) VRM drive. The results of the optimisation indicate the importance of considering inverted losses when performing the optimization. Inverter losses are shown to be comparable to motor losses, imparting significant influence on the excitation design. The stability implications of the optimal-efficiency excitation are discussed, including the necessity for closed loop control. In addition, the experimental VRM drive design is critically reviewed based on the breakdown of inverter and motor losses. Allowable excitation parameter variations and the dependence of the optimal excitation on load torque are also discussed.