Power Cycling Capability Of Igbt Modules And Inverter Power Units; General; Igbt Module With Cyclically Alternating Current Load - Siemens SINAMICS G130 Engineering Manual

1.11 – – –

1.12 Power cycling capability of IGBT modules and inverter power units

1.12.1

General

The term "Power cycling capability" refers to the capability of a component, for example, a fuse or an IGBT module,
to withstand temperature fluctuations caused by an alternating current load during operation without suffering
premature wear or failure.
To ensure that the IGBT modules used in the SINAMICS power units are always operated within a range of a
sufficient power cycling capability, the following aspects must be considered at the drive configuring stage. A
sufficient power cycling capability necessitates either the prevention of critical operating conditions or proper over-
dimensioning of the units themselves.
The following sections explain the physical background and give dimensioning guidelines for selecting IGBT modules
and thus power units to ensure a sufficient power cycling capability for the application in question.
1.12.2

IGBT module with cyclically alternating current load

The diagram below shows the internal design of an IGBT module plus the temperature characteristics of the IGBT
chip, the base plate and the heatsink when the chip is subject to a cyclically alternating current load.
Design of an IGBT module and temperature characteristics with a cyclically alternating current load
Owing to the mechanical design of the IGBT module which comprises several layers of different materials, there is a
relatively high thermal resistance between the IGBT chip in which the heat losses occur, and the base plate of the
IGBT via which the heat losses are discharged to the power unit heat sink. As a result, there are very significant
fluctuations in the temperature of the IGBT chip when it is subjected to a cyclically alternating current load, while the
temperatures of the base plate and heat sink remain relatively constant.
Under critical operating conditions, temperature cycles with such a high temperature swing ΔT
IGBT module is subjected to substantial thermal stressing, resulting in a significant reduction in the IGBT lifetime.
This is because the number of permissible temperature cycles of an IGBT is limited and is further reduced as the
temperature swing ΔT
Chip
increase in temperature swing ΔT
Critical operating conditions with severe cyclic fluctuations in the IGBT chip temperature include the following
scenarios:
·
Periodic load duty cycles with pronounced load current fluctuations combined with short duty cycle times
·
Operation at low output frequencies combined with high output current
Fundamental Principles and System Description
Cyclically alternating current load
increases. As a consequence, the lifetime of the IGBT is also reduced in proportion to the
.
Chip
Engineering Information
SINAMICS Engineering Manual – November 2015
T
Base plate
T
Heatsink
Bond
wire
Base plate
Heatsink
can occur that the
Chip
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