The authors have established that in the operating mode some amount of the bulk material can be considered conditionally stationary against the sieve mill, and it can contribute to the inertial load. The rest of the bulk material remains movable and provides the main part of the dissipative load. Allowing for inertia and mobility of the bulk material, the authors calculated the inertial and dissipative power of the actuator, with the inertial power exceeding more than eight times the dissipative one. This paper shows that the use of the kinematic scheme for the screen grader with the shift of oscillation phases of two sieve mills against each other by a quarter of the oscillation period prevents the consumption of the electric power equal to the inertial one, and leads to five time reduction in irregularities of dissipative power.