1) An unbalanced delta-connected load on a 400 V (line-line) 50 Hz system has impedances of: Za = 40 ohm; Zb = j 40 ohm; Zc = 20 j 20 ohm. Calculate the phase and line currents. 2) A star-connected 400 V resistive load is connected to a 3-wire system. The load has impedances of: Za = 20 ohm; Zb = 40 ohm; Zc = 40 ohm. Calculate the voltage of the neutral point. 3) An unbalanced star-connected load on a 220 V 60Hz 4-wire system. The legs of the load have impedances of: Za = 5 ohm; Zb = 5 +j 5 ohm; Zc = 5 j 5ohm. To insure correct phase voltage the star is connected to the neutral line Calculate the phase and neutral currents. 4) An 400 V (line-line) star-connected unbalanced load has an earthed start point. The load on phase 1 is 10 ohm, the load on phase 2 is 10 + j5 ohm and the load on phase 3 is 10 j5 ohm. Calculate the phase currents and the star to earth current and sketch the current phasor diagram. I can do the balance system but the unbalanced I can't. and I would like to ask what is the diffrenece between xxx V (line-line) and xxxV xxHz and the difference between the 4-wire system and 3-wire system. thank you.