Using a general-purpose inverter to drive a three-phase induction motor can save energy under the following two types of loads (application): 　
　
1. Constant-torque load (load of which torque is constant even when speed changes)
This load type is represented by a conveyor and cart and reducing the speed saves energy. 　
　
2. Square variable-torque load (load of which torque is in proportion to the square of speed)
This type of load is represented by a fan, pump, and blower. Since the shaft power is in proportion to the cube of speed, reducing the speed drastically saves energy. For example, reducing the speed to 1/2 reduces energy consumption to 1/8. 　
　
The energy saving effect depends on the load and speed.