Environmental Engineering Reference
In-Depth Information
a tendency to latch-up due to current injection at the third junction unless some
effort is expended in forcing the current gain of this junction to be low enough to
inhibit latch-up.
The volt-ampere capability of available power semiconductor switching devi-
ces is summarized in Figure 4.21 to contrast their power handling capability with
switching frequency capability. Device terminology is explained in Table 4.12,
including inventorship and year introduced.
10 k
GTO
Higher voltage, higher current
Higher frequency
1k
IGBT/CSTBT
BJT
100
DMOS
10
0.1
1
10
100
Frequency (kHz)
Figure 4.21 VA versus frequency capability of power semiconductors
4.3.2 kVA/kW and power factor
In this section, the key aspects of power semiconductors will be introduced and the
relationship of V-A apparent power based on device ratings versus real power
throughput. Virtually all power electronic inverters for hybrid propulsion employ
IGBT device technology. There has been some misconception regarding this
technology, particularly in terms of what is a 'motor-drive' IGBT. This section will
address that concern.
Power semiconductor devices range in voltage withstand capability of from
3 kW to 6.5 kV and current magnitudes of 3-4.5 kA. Thyristors have the highest
kVA ratings, but are generally slow switching. The gate turn-off thyristor (GTO) is
capable of switching 3 kA at 4.5 kV but is limited to less than 700 Hz. The emitter
turn-off thyristor (ETO) is capable of simultaneously switching 4 kA at 4.5 kVA at
relatively high frequency. IGBTs are making enormous progress in both voltage
and current ratings, with some IGBT introductions being capable of 6.5 kV and
3.5 kA (not simultaneously), and high frequency versions are capable of processing
kilowatts at switching speeds of up to 100 kHz (e.g. ultra-thin IGBTs).
Figure 4.22 is a cross section of the two principal varieties of IGBTs, the
punch-through (PT) and non-punch-through (NPT) device structure [24,25].
