Overview
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Current is carried through busbars, or wire bondings, as a supply line
of electrical power.
Parts, such as components used in inverters to handle variable frequencies,
produce an increased amount of heat due to the resistance cause by a skin
effect that increases as the frequency of the current flowing through the
circuit gets higher.
A design that accounts for the heat and temperature distribution of each
frequency is vital because the excess heat causes a reduction in efficiency
or damages the device.
The temperature distribution can be evaluated by treating the Joule losses
obtained from the magnetic field analysis as the heat source.
This example presents the use of a coupled magnetic field and thermal analyses
to obtain the temperature distribution in a busbar when the frequency of
the power supply is changed. |
Current Density Distribution / Frequency Characteristics of the Joule Losses
| The current density distribution for each frequency is indicated in Fig.
1, and the frequency characteristics of the Joule losses are indicated
in Fig. 2. The current density in the wire bonding and the thin copper
sheet increase as indicated in Fig. 1.The Joule losses increase as the
frequency increases, as indicated in Fig. 2. The cross-section area where
the current flows decreases due to the resistance that increases because
or the skin effect. |
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Temperature Distribution / Frequency characteristics of the Average Temperature
| The temperature distribution of the busbar is indicated in Fig. 3, and
the frequency characteristics of the average temperature are indicated
in Fig. 4. The temperature increases with the current density in the wire
bonding and thin copper sheet for all of the frequencies. The temperature
at 1 MHz suddenly increases when compared to 10 Hz and 100 Hz. Note that
caution needs to be used because the increase in temperature can not only
burnout the busbar, but damage the device as the thermal stress increases. |
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