Ordinary inverter uses a diode bridge rectifier converts AC power to DC, then using IGBT inverter technology DC into AC voltage and frequency is adjustable to control AC motors. This converter can only work in the electric state, so called two-quadrant drive. As the two-quadrant inverter using a diode rectifier bridge, unable to achieve two-way flow of energy, so there is no way to power the motor feedback system back to the grid. In some motor regenerative applications, such as elevators, hoists, centrifuge systems, pumping units, high-speed planer, can only increase the resistance of the brake units on two-quadrant inverter, the energy consumed by the motor feedback . In addition, power diode rectifier bridge would have serious harmonic pollution.

NGF600 series of four-quadrant inverter use PWM controlled rectifier technology, so that the energy can flow in both directions, on the one hand you can adjust the input power factor of the power grid, eliminating harmonic pollution on the grid, allowing the drive to truly become "green products ", on the other hand can contribute to the energy generated by the electric motor to power the anti achieve significant energy saving effect.