AC POWER FACTOR
The increase in harmonics in a power circuit (Fig. 10.9) will decrease the total power fac- tor. It can drop to 60 percent for an inverter without a dc link reactor. Obviously, this is not acceptable. The problem is solved by adding a dc link reactor in series with the capacitor bank. If the reactor is chosen large enough, the diode bridge will always see an inductive load. The total power factor will increase to 0.95.
AC Input Power Changes with AC Input Voltage
The output inverter of the drive is a separate entity from the input source converter. They operate independently from each other. Assume that the drive is feeding a constant kilowatt load near its full rating. If the ac line voltage drops by 10 percent, the line alternating cur- rent increases by 10 percent. This will overload the drive.
The current increase due to the reduction of ac line voltage will be added to any current unbalance caused by a line voltage unbalance.