Model of voltage drop and losses of carbon brushes. For currents
between -ILinear and ILinear the voltage
drop shows a linear behavior as depicted in Fig. 1. For positive
currents greater or equal than ILinear the voltage
drop equals V. For negative currents less or equal
than -ILinear the voltage drop equals
-V.
|  | 
| Fig. 1: Model of voltage drop of carbon brushes | 
The voltage drop v is the total voltage drop of all
series connected brushes.
If it is desired to neglect brush losses, set
brushParameters.V = 0 (this is the default).