IXBOD1-40R Datasheet, PDF (6/8 Pages) IXYS Corporation – Breakover Diodes

Application
Protection of thyristors against overvoltages in forward
i
direction.
V_BO (T_VJ) = V_{BO, 25°C} [1+KT(T_VJ - 25°C)]
Thyristor
BOD
V_D
Calculation example
a. The maximum junction temperature shall be
calculated for a module IXBOD 1 -30R at an
ambient temperature T_a = 60 °C, an exponentially
decaying current I_TM = 40A, a pulsewidth tp = 2 µs,
an operating frequency f = 50 Hz and natural
convection. From the diagram Fig. 6 the energy per
pulse is obtained:
E_p1 = 6 x 10^-3 Ws
For a module IXBOD1-30R the number of single
IXBOD elements is:
n=3
At natural air cooling the thermal resistance junction
to ambient amounts to (Fig.8):
R_thJA = 20K/W
and the unknown temperature can be calculated as:
T_VJmax1 = T_a + n • f • E_p • R_thJA + K_p • E_p
T_VJmax1 = 60 + 18 + 4.2 = 82.2°C
b. If following these steady-state conditions an
overload for 1 minute occurs with I_TM= 60 A and a
pulse-width tp = 4 µs at the same operating
frequency f = 50 Hz, then the resulting maximum
junction temperature is calculating as follows:
T_VJmax2 = T_VJmax1 + (E_p2-E_p1) • n • f •Z_thJA(t) + Kp • (E_p2-E_p1)
The diagrams Fig. 11 and Fig. 8 show
E_p2= 14x10^-3 Ws
Z_thJA(t = 1min) = 12K/W
From what follows:
T_VJmax2 = 82.2 + 14.4 + 5,6 = 102.2 °C
which is allowed because the maximum admissible
junction temperature T_VJM = 125 °C.
H-6
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