Discussion in 'Homework Help' started by Cerkit, May 16, 2010.

  1. Cerkit

    Thread Starter Senior Member

    Jan 4, 2009
    Can someone explain why and active front end (back to back inverter) improves power quality as opposed to usind simple diodes for the front end (rectifier) of the inverter?
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    When you said active, I think you should know.
    Active takes care of the passive losses increasing efficiency
  3. mik3

    Senior Member

    Feb 4, 2008
    It allows a bi-directional power flow which allows for the motor to operate in all 4 quadrants (motoring and breaking). Bi-directional power flow means that when the motor is breaking and the DC link capacitor is charged up, by proper switching of the front end the breaking power is delivered to the grid. A brake chopper could be used but if breaking is going to happen often a lot of energy will be wasted.
    Also, an active front end allows for power factor correction by forcing the input current to the converter to be sinusoidal and in phase with the grid voltage.
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    By power quality I assume you mean harmonic issues on the front-end rectifier side .....

    The following link gives a detailed overview of the value of active control of the rectifier current & reduction of line side harmonics in UPS.