Portable AC Drawing 0.33 Amps Trips 15 Amp Circuit Breaker?
I agree with others .33a no way for even the smallest ac units. At 5 minutes I believe the circuit is being overloaded.
Most breakers for residential use are inverse time breakers. A 15 amp breaker loaded at 15.5 amps may not trip for a 1/2 hour push it to 16 amps and it will trip much quicker possibly 5 minutes.
I would check the load on that breaker with a clamp meter and would expect more than 15 amps. If the load is less than 15 the breaker is defective and needs to be replaced.