In lighting stations, for example, we have three principal kinds of apparatus. Boilers produce the steam that runs the steam engines, and these run the dynamos that give the current. Besides these there are many other things needed. The electrical energy that goes over the wires to furnish light, heat, and power, really comes indirectly from the coal that is used to boil water and convert it into steam. The various parts of the central station merely aid in this transformation of energy.
The dynamos are connected to the engines by belts, or they are direct connected. Figs. 250, 251, show dynamos connected to engines without belts.
The current from the dynamos is led to large switchboards which contain switches, voltmeters, ammeters, lightning arresters, and various other apparatus for the proper control and measurement of the current. From the switchboard it is allowed to pass through the various street mains, from which it is finally led to lamps, motors, etc.
Fig. 250.
Fig. 251.
Water-power is frequently used to drive the dynamos instead of steam engines. The water turns some form of water-wheel which is connected to the dynamos. At Niagara Falls, for example, immense quantities of current are generated for light, heat, power, and industrial purposes.
