0195136047.pdf

16.1 POWER SEMICONDUCTOR-CONTROLLED DRIVES 769

T 1

T (^4) T 1
T 4
A
iA
T 3
T 3
T 6
T 6
B N B
A
C
T 5
T 2
T (^2) T 5
Stator
windings
C
Figure 16.1.16Three-phase symmetrical ac voltage-controlled circuits.
A
B
C
A
B
C′
A′
Motor
C
Figure 16.1.17Four-quadrant ac voltage controller.
FREQUENCY-CONTROLLEDINDUCTION-MOTORDRIVES
The converters employed for variable-frequency drives can be classified as:

• Voltage-source inverter (which is the only one considered here)


• Current-source inverters


• Cycloconverters, which allow a variable-frequency ac supply with voltage-source or
  current-source characteristics obtained from a fixed-frequency voltage source.