IGBT Modules - Technologies, Driver and Application (Second Edition) - page 177

165
Fig. 4.5
Relationship between the capacitance of a plate capacitor and thermal capacity
Electrical capacitance C
el
(stated as the unit
 ⋅
V
sA
) is derived from the relationship
between the chargeQand theapplied voltageU.
Fig. 4.6
Thermal capacity of a flat plate
The thermal capacity C
th
(also known as heat capacity), stated as the unit
K
J
is
derived from the relationship between the heat Q
th
and the temperature difference
T. In
other words, the thermal capacity can be described as the amount of energy stored
uponeach change in temperature.
T
Q C
th
th
=
Eq. 4.5
The heat Q
th
can be described according t
by the specific thermal capacity c
th
,
themassmand the temperature difference
T.
Tmc Q
th
th
∆⋅ ⋅
= ∆
Eq. 4.6
The specific thermal capacity c
th
is expressed as amaterial constant in the unit
Kkg
J
. I
if
Q
th
is replaced b
the relationship for thermal capacity
C
th
is:
mc C
th
th
=
Eq. 4.7
1...,167,168,169,170,171,172,173,174,175,176 178,179,180,181,182,183,184,185,186,187,...548