In our company, a discussion is raging on whether a motor with a frequency controller should be protected with an automatic circuit breaker with B or C characteristic. 

The B-camp's argument is that, because of frequency controllers or soft-starters, the inrush current on a motor is much lower so a B trip characteristic should be sufficient. The C-camp believes that using B characteristic is just not allowed.

Are there any reasons to still use a C-characteristic circuit breaker?