My granfather would say this: JUNGE, JUNGE ..
Dear friend, have a look at the following rough estimations:
14kW motor (divided by a typical pf≈0.9) gives you ≈15.5kVA .. divided by 3-phase voltage, say 400Vac, that is ≈39A ..
As a rule of a thumb you have to select a circuit breaker that is ≈ 2 x rated current but if 20A circuit breaker trips only from 'time to time' you may be just right with 63A-rated unit ..
So, replace 20A circuit breaker with 63A one and it should stop tripping ..
Regards,
IanP