Three power circuits are used to deliver 30 kW power to three 10 kW-load or two 15 kW-load.
Theoretically, all three circuits do their job very well. However, three main practical concerns have to be taken into account:
1. size of the wire
2. resistive losses
3. danger of electric shock at the load terminals
The first two of them can be handled by reducing the amount of the current through the wires, while the third can be handled by reducing the voltage drop across the loads.
Three candidate design is used to reveal the best one dealing with these concerns:
1. Single-phase
wire current: 250 A
voltage across each load: 120 V
2. Split-phase (120/240)
wire current: 125 A
voltage across each load: 120 V
neutral wire is used to deal with the consequence of opening a load.
3. Three-phase (120/208)
wire current: 83.33 A
voltage across each load: 120 V
again neutral wire is used to deal with the consequence of opening a load.
