Planar motors have wide application prospects in many high-precision industrial apparatus. In this paper, an operable coil-switching strategy for planar motors is systematically presented. This strategy can reduce about 15% ohmic loss by shutting down the ineffective coils. More importantly, we put forward a novel 2-step minimal-ohmic-loss transformation from the net force to the phase current for the first time. Compared with previous studies, this 2-step method can reduce the calculation amount of the drive currents remarkably. Moreover, this method can be used to analyze the relationship between the actuator-force allocation and the ohmic loss. The validity of this 2-step method is verified with a detailed analytical proof. At last, an ohmic-loss reduction control strategy for the prototype is proposed and its performance is analyzed in detail. The same approach can be applied to similar types of planar motors with the structure of symmetrical three-phase windings.