DG-IRMCK203 Datasheet, PDF (59/67 Pages) International Rectifier – Application Developer’s Guide

IRMCK203 Application Developer’s Guide
SVPWM Gain
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
1000
2000
3000 4000
M
5000
6000
7000
Figure 22. Transfer Characteristics
The maximum achievable modulation (Umag_L) in the linear operating range is given by:
Umag _ L = 2²⁵ * 3 / Mod _ Scl
Over modulation occurs when modulation Umag > Umag_L. This corresponds to the condition where the voltage
vector in Figure 23 increases beyond the hexagon boundary. Under such circumstance, the Space Vector PWM
algorithm will rescale the magnitude of the voltage vector to fit within the Hexagon limit. The magnitude of the
voltage vector is restricted within the Hexagon; however, the phase angle (θ) is always preserved. The transfer gain
(Figure 22) of the PWM modulator reduces and becomes non-linear in the over modulation region.
V3
sector 3
V4
V2
Requested
sector 2
Voltage Vector
Generated
Voltage Vector
sector 1
V1
U-phase
sector 4
sector 6
sector 5
V5
V6
Figure 23. Voltage Vector Rescaling
This document is the property of International Rectifier and may not be copied or distributed without expressed consent.
59