Weird question, a 2 pole 200A single phase breaker into a 3 phase 208/120V 200A three phase panel

[Cartoon1]

I was just thinking about this scenario. Technically a 200A 3 phase panel load capacity is capable of supporting a 200A single phase load. Assuming the electrical panel can support a sub-feed 2 pole type 200A breaker. Also assume there is other loads on the panel for a total of 10KVA made out of 120V single pole circuits. Wouldn't this be an issue since phase A and B will be pulling close 200A and then you take into consideration tha 120V 1 pole breaker load amperage on phase A and B will add to the amperage of 200Amps or more, wouldn't this exceed the panel 200A ratings and trip possible the main breaker...... even though the panel capacity is capable?
Have you run into this situation?

Thank you

 

[jaggedben]

If you draw more than 200A on any leg of a 200A common trip breaker, then yes you'll trip the breaker.

Probably you should not be putting a 200 branch breaker in a 200A panel if the load is actually 200A and there are lots of other loads in the panel. The code does not prohibit the breakers on a bus to exceed the bus rating, but it does require the bus to meet the calculated load. See article 220.