Why does a three-phase input automatic drive knock out?

Hello. At night, the input 3-phase automatic machine 63A was knocked out twice, two 3-phase boilers worked (7 kW in the garage and 12 kW in the house). After the first shutdown he turned it on, after a while it knocked out again. After that, he turned off one boiler (garage), shutdowns stopped. In the morning I turned it on, everything works. What is the reason - I do not understand.