Power is force times velocity. Magnetic saturation density and current intensity limit the electromagnetic force but do not limit the speed of the electric drive. Due to the limitations of moving parts, the speed of hydraulic motors is difficult to improve in the future. The only problem that limits the motor rotation speed is the imbalance between the bearing and the rotor. Therefore, the power density of high-speed motor can exceed that of hydraulic motor. Therefore, when new energy sources are available and electricity will be readily available, the hydraulic motor may be the first to be challenged in the mobile hydraulic system. "Wheel-edge electric drive" has emerged at the 2018 Hanover industrial fair. Because the inertia of the electric drive is large and the flexibility is poor, it is possible to win only in applications where the speeds are less drastic.