Basically, respectively, in the direction of energy, generators are borrowed by the load (such as hydro, wind), mechanical energy, kinetic energy into electricity, without load, the generator does not have current flow. Electric motors and power electronics, micro-controller to comply with the formation of a new science, known as motor control. Before using the motor needed to understand their use of power DC or AC power, if it is AC, also need to know whether it is three-phase or single-phase alternating current, a wrong power supply can lead to unnecessary losses and dangerous.
After the motor without load or a lightly loaded Motors speed faster, induced electromotive force is strong, at both ends of the motor voltage, supply voltage minus the induced voltage, so the current weakening. Ruomada is under a heavy load, slow rotation induced EMF is small, and therefore power must provide high current (power) to correspond to the requirements of higher power output/performance.