Motor rotor voltage by three-phase controlled rectifier into a DC voltage when the chopper lGBT tube conduction, the rotor current is chopper short circuit, the formation of the motor shaft power output; when the chopper is open, the rotor DCcurrent inverter with feedback into the motor feedback windings or inverter transformers.
The formation of the slip power, thereby reducing the stator absorb the energy from the grid, changing the duty cycle of the chopper, that is to change two parts of the current allocations in order to achieve speed control.
IGBT inverter speeder SPWM control of the sine wave inverter output current is sinusoidal, harmonic minimal, the inverter can be output ahead of the reactive power compensation motor itself lagging reactive power, total power factor high. SCR inverter with the common lag shift trigger control different.
Speed control is not changing the inverter angle instead of using a fixed minimum 25 ° phase angle, through the mediation chopper duty cycle, taking into account the sudden power failure, etc., the installation of a protection circuit consisting of subversion by the lGBT completely overcome the inverter inverter with subversion problems and improve reliability.