The right choice for the inverter control system uptime is critical. We must fully understand the inverter-driven load characteristics when selecting the drive. In practice, people often will produce mechanical divided into three types: constant torque load, constant power load and the fan and pump loads. 1, the load torque TL constant torque load and speed n independent of any speed TL always remains constant or substantially constant. Such as conveyor belts, mixers, extruders friction class load and crane, hoist, etc. are all potential energy load constant torque load. Drag the constant load torque when the drive nature, the torque at low speed to be large enough and has enough overload. If you need constant run at low speed, it should be considered a standard asynchronous motor cooling capacity, avoid excessive temperature rise of the motor. Torque, generally inversely proportional to the rotational speed 2, the power load spindle and rolling mill, paper machine, plastic film production line coiler, decoiler and other requirements, which is called the constant power load. Constant power nature of the load should be on certain terms of the speed range. When the speed is very low, by limiting the mechanical strength, TL can not grow indefinitely, into a constant torque properties at low speeds. Constant power region and constant torque load has a great impact on the choice of the transmission program. Motor speed in the constant flux, the maximum allowable output torque constant, constant torque speed belongs; in weak magnetic speed, the maximum allowable output torque and speed is inversely proportional to belong to constant power speed. If constant torque and constant power range of constant torque motor and constant power speed range is consistent with the load, the so-called "match", the capacity and the capacity of the drive motor are minimized. 3, square torque load at various fan, water pump, oil pump, resistance is proportional to the square with the rotation of the impeller, air or liquid within a certain speed range corresponds approximately with the speed of n. With the decrease of speed, torque is reduced by the square of the speed. This load power and speed is proportional to the third power required. When the desired amount of wind, the flow is reduced, the use of the drive to regulate the air flow, the flow through the governor's way, it can greatly save energy.