Hitachi IGBT Module Application Manual
5.4.3.4
5.4.3.4.1
Necessity for Symmetry of Main Circuit Wiring
Wiring Equalization
For IGBT modules to be connected in parallel, it is essential to equalize the wiring on the collector and
the wiring on the emitter with each other to keep inductance values in balance.
circuit including main circuit wiring inductance circuits.
For the collector, wiring inductance circuits L
CA
and L
CB
are shown, and for the emitter, wiring
inductance circuits L
EA
and L
EB
.
When IGBTs (A) and (B) are turning ON, the current generated on each individual collector depends on
the variations of the inductance circuits rather than on each element’s characteristics.
Because the current balance depends principally on the inductance ratio, it is important to keep
symmetry in wiring by matching the inductance values. For example, referring to Figure 30, if L
CA
and L
CB
are unbalanced (that is, L
CA
> L
CB
) and the V
CE
(sat) value of IGBT (A) is smaller, then the current
sharing as depicted in Figure 31 will result. In particular, if emitter lines L
EA
and L
EB
are unbalanced, the
IGBT gate voltage will be adversely influenced, causing an unbalanced current.
Figure 30. Wiring to equalize main wiring inductance values
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