2.3.1 Shunt Resistors

The phase currents are sampled by the phase shunt resistance $R_{s h u n t}^{p h a s e}$ $R_{s h u n t}^{p h a s e}$ and the DC bus current is sampled by the DC bus shunt resistance $R_{s h u n t}^{b u s}$ $R_{s h u n t}^{b u s}$ . Both $R_{s h u n t}^{p h a s e}$ $R_{s h u n t}^{p h a s e}$ and $R_{s h u n t}^{b u s}$ $R_{s h u n t}^{b u s}$ are 0.025Ω by default.

Normally, the phase currents or DC bus current sample signals are regulated and sent to the ADCs for conversion on the control board.

The range of the current which can be converted is determined by the shunt resistance on the control board. Take the phase current as an example, suppose the range is:

$[- I_{r a n g e}^{p h a s e}, + I_{r a n g e}^{p h a s e}]$ $[- I_{r a n g e}^{p h a s e}, + I_{r a n g e}^{p h a s e}]$ , then $I_{r a n g e}^{p h a s e} \times R_{s h u n t}^{p h a s e} \times G^{p h a s e} = \frac{1}{2} A V D D$ $I_{r a n g e}^{p h a s e} \times R_{s h u n t}^{p h a s e} \times G^{p h a s e} = \frac{1}{2} A V D D$ , then $I_{r a n g e}^{p h a s e} = \frac{A V D D}{2 \times R_{s h u n t}^{p h a s e} \times G^{p h a s e}}$ $I_{r a n g e}^{p h a s e} = \frac{A V D D}{2 \times R_{s h u n t}^{p h a s e} \times G^{p h a s e}}$ .

Where,

$G^{p h a s e}$ $G^{p h a s e}$ is the regulating circuit’s gain for the phase current sample signal

AVDD is the analog power supply voltage for the ADC.

$G^{p h a s e}$ $G^{p h a s e}$ and AVDD are fixed for a certain control board, while $R_{s h u n t}^{p h a s e}$ $R_{s h u n t}^{p h a s e}$ can be modified by the user. Therefore, $I_{r a n g e}^{p h a s e}$ $I_{r a n g e}^{p h a s e}$ is determined by $R_{s h u n t}^{p h a s e}$ $R_{s h u n t}^{p h a s e}$ . The user can modify the $R_{s h u n t}^{p h a s e}$ $R_{s h u n t}^{p h a s e}$ to achieve a desired $I_{r a n g e}^{p h a s e}$ $I_{r a n g e}^{p h a s e}$ .

Similarly, the user can modify the $R_{s h u n t}^{b u s}$ $R_{s h u n t}^{b u s}$ to achieve a desired $I_{r a n g e}^{b u s}$ $I_{r a n g e}^{b u s}$ .