IGBTs are exposed to strong thermo-mechanical load variations, which lead
to aging, material fatigue abrasion and finally outage. The switch losses and
the resulting temperature rises in the IGBT semiconductors can be considered
as constant for frequencies of 50 Hz and more. For lower frequencies, the
ON and OFF switching is so slow, that it results in a time-dependent temperature
behavior of the chips. The life expectancy of an IGBT type is defined by
the number of temperature cycles; this rapidly falls by increased amplitude of
the chip temperature variation.

IGBT chips used for the control of the
traction motors of metros might experience during their period of use up to 1
to 10 Million load changes with a temperature variation between 15K and 40K.
When neither the chips nor the connections can be upgraded, then the
temperature variations must be reduced with more efficient cooling.

*Surface temperatures of the IGBTs and diodes for a 0.1 Hz frequency *

(video frequency is real frequency), fan on the left

*Surface temperatures of the IGBTs and diodes for a 1 Hz frequency (video frequency is real frequency), fan on the left *

In this example the IGBTs and diodes are integrated into a Semikron power-module, which is mounted on a heat sink. The produced losses will be evacuated by forced convection through the cooling fans.

These calculations have been performed with the commercial software FloEFD by switching on the transient option. The time step is one-hundredth of the period. The time dependence of the losses is given as input. It is known for such applications that the heat radiation is negligible as the temperatures are too low, therefore it does not need to be simulated. The natural convection is calculated in the casing by switching on the gravitation option of the solver. Thanks to the friendly user interface, the embedment in the CAD tool and a multi-processor solver, the results could be reached quickly.

The calculation domain has been spilt in ½ Million cells for ½ a module. For the calculated worst case with a frequency of 0.1 Hz, the IGBT temperatures vary between and 45 and 60°C. This corresponds to only 1 Million cycles or one-year normal operation of an on-shore wind power station.

*Air temperatures in an IGBT module casing for a 0.1 Hz frequency, (video frequency is real frequency)*

*Air temperatures in an IGBT module casing for a 1 Hz frequency, (video frequency is real frequency)*

Low frequencies for on-shore wind power stations

On-shore wind power stations are mostly equipped with double-fed asynchronous generator with lip-ring rotor. The rotor windings are excited with a regulated low frequency current, typically between 0.1 and 10 Hz.

On-shore wind power stations are mostly equipped with double-fed asynchronous generator with lip-ring rotor. The rotor windings are excited with a regulated low frequency current, typically between 0.1 and 10 Hz.

It enables the production of current with the network frequency directly
at the generator, independently from the last changes due to changes in the wind
speed. The transistors of the frequency converter show strong temperature
variations; a more efficient thermal path must be designed with the help of 3D-CFD.

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Electrical Machines

Cooling large motors

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Electrical calculations

Cooling calculations of motors and generators

Cooling of power electronics

Cooling of IGBT at low frequencies

CFD Engineer Consulting

Karim Segond

Videos of Segond

Guenter Zwarg

Guenter Siegl

Heating, Ventilating and Air Conditioning with CFD

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3D CFD Flow simulations

Hydraulics

Physical considerations

3D CFD Mesh

CFD Calculation model

CFD Calculation programs

Electrical Machines

Cooling large motors

Cooling medium motors

Electrical calculations

Cooling calculations of motors and generators

Cooling of power electronics

Cooling of IGBT at low frequencies

CFD Engineer Consulting

Karim Segond

Videos of Segond

Guenter Zwarg

Guenter Siegl

Heating, Ventilating and Air Conditioning with CFD

Privacy Policy