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Specific application of laminated busbar
1 Original design
The parameters of the design scheme of one of our customers' inverter units are as follows:
The DC bus voltage Vd=800V, the current flowing through the IGBT I=125A, the stray inductance of the busbar is about 760nH, and the selected IGBT rated voltage is 1700V.
In the original design, the bus bar was directly connected with copper bars, so the mutual inductance between the positive and negative bars would be very large. Based on the principle of electromagnetics, we roughly calculated it to be about 760nH. The specific formula is as follows:
In the formula: μ0 is the vacuum permeability; μr is the relative permeability of the conductor, l is the length of the conductor, w is the width of the conductor, and d is the gap between the upper and lower layers [1].
In this way, the customer must leave more margin when selecting IGBT, that is, the IGBT with a rated voltage of 1700V is selected, and the customer also needs to use an absorption capacitor with a rated voltage of 1700V and 2.0μF to absorb the voltage spike, so as to barely meet its performance requirements.
In addition, in this structure, the fan adopts the form of air blowing for heat dissipation. For the IGBT of AC output A phase, the heat will be accumulated and the temperature rise will be very high, which will affect the stability of its operation.
And without designing a special air duct, the overall heat dissipation will be greatly affected.