The paper presents an analytical technique by which the on-state losses in the devices in a PWM inverter may be calculated. It takes the regular type of symmetrical double-edge sinusoidal modulation, assumes that the load current is sinusoidal, and shows that the inherent Bessel Function solution can be reduced to a simple algebraic form when the frequency ratio is greater than ten or so. It is assumed that the on-state voltage drop across an active device and a free-wheel diode is made up of a constant component plus a component that is linearly dependent upon current. The results are, therefore, applicable to most semiconductor devices. Experimental results are presented and are shown to be in good agreement with predictions.