# Why are inverter bus bars made overlapping?

A lot of literature on bus bar design suggests that bus bars should be made to overlap or have equal area such as this.

The reason they mention is the total stray inductance falls due to increase in mutual inductance.

Bus bars represented by parallel conducting plates: If top plate represents the top DC bus and bottom plate represents the bottom DC bus, the total inductance according to the paper is:

$$L_{tot} = 2 \times (L_{self} - L_{mutual})$$

Where $$\ L_{tot} = Total inductance of bus bar, \$$

$$\ L_{self} = Self inductance of bus bar, \$$ $$\ L_{mutual} = Mutual inductance between top and bottom plates \$$

But if currents are flowing in opposite directions are, should the formula not be:

$$L_{tot} = 2 \times (L_{self} + L_{mutual})$$ by right hand thumb rule - but then increasing overlap area and increasing mutual inductance would not make sense, yet that is how most bus bars for inverters are engineered.

Can someone please tell me what is the correct explanation of this?

• To minimize inductance. Sep 14 at 7:33
• I guess the equation already takes into account that currents flow in opposite directions, you can see it on depiction. Sep 14 at 9:47 