Steamhead is correct, three phase (ac) can be configured delta or star. Delta is where the outputs from the three phases come off the corners of what can be visualised as a triangle, each side of the triangle being one of the three phase windings.
In a star configuration each of the three phase windings are connected at one central point, the other ends of the phases being visualised as radials, the ends of which are not connected together, but from which outputs can be connected. This resulting in 440Vac nominal from any two end points in conventional UK distribution. An output can also be connected to the centre point and the voltage from this point to any outer end point will be 220 Vac nominal in the UK.
However the advice is don't connect anything to anything unless you fully understand the whole installation, and certainly not with an aircraft (DC) installation