21-06-2012, 01:28 PM
It depends on where you are and the kit installed. They tend to use one phase for one direction from the substation and a second in the opposite direction with a neutral sectioon between to keep the phases apart. The third phase is not normally used for traction. DC substations have rectifiers but in the old days rotary convertors were used to create a raw DC current. You usually find DC substations around 3 miles apart compared to 20-25miles for AC due to the poor efficiency of DC 3rd rail traction.
MG/MA sets are not normally used under AC conditions unless the stock is dual voltage in nature but even MG/MA sets are being phased out for solid state equipment. One exception, there is a rail in Namibia that is 25kv overhead but the locos have MA sets because of the long power sections, the volys drop down to as little as 15Kv mid section so the MA ensures the auxiliaries work correctly.
Much more impressive, look up DC booster sets, very clever design.
MG/MA sets are not normally used under AC conditions unless the stock is dual voltage in nature but even MG/MA sets are being phased out for solid state equipment. One exception, there is a rail in Namibia that is 25kv overhead but the locos have MA sets because of the long power sections, the volys drop down to as little as 15Kv mid section so the MA ensures the auxiliaries work correctly.
Much more impressive, look up DC booster sets, very clever design.
