Hitachi RAS-25CNH1 - Waveform of Transistor Base Current

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● When pin e of HIC-1 then goes "Hi" [ "Lo", a photocoupler between PQ2 pins 1 and 2 turns off and
the reverse bias current flows to C501 [ power module’s Eu
+
terminals [ Bu
+
terminals [ R504 [
PQ501 Switching incomplete to cut off the upper arm transistors. (Fig.7-3)
● R507 is used to charge C501 initally.
● The operation is the same for B
+
and C
+
phases.
5
6
1
8
2
PQ2
7
b
a
1
Bu
+
Eu
+
Power module
A
+
phase
+
—
A
2
R401
R404
D401 D402
C401
R407
A
Current at point
Reverse
bias
current
O
A
Fig. 7-3 Waveform of Transistor Base Current (Reverse Current at Point )
A