Three groups of resistors are connected in star to one three-phase grid with line voltage U1 = 400V.Each group consists of fifty resistors in parallel, each with a power of 60W at 230V. The neutral is not connected. What is the impedance of the 50 resistors in parallel? What are the currents through each branch? The 50 resistors are removed from one of the three phases. The resistances are retained in the other two phases. What are voltages and currents if there are in one of the groups no resistors are switched on? Draw the vector diagram and determine the total used power in the whole load.