If the generating set doesn’t put up the demanded performance after having been started as prescribed and having reached the right engine speed, you will have to check the following points:
check if the engine speed is high enough and if it remains stable
disconnect all the loads, so that the generating set can work without any load
check if the cables and plugs are damaged
check if the connections are correct and if the capacitors have enough power
check if the sockets and the fuses are damaged
check if the stator’s windings are connected properly
check if there is a short circuit in the stator windings