Ans. It should be handled carefully to avoid any injury to the wires of the winding and their insulation.
If it become necessary to lay the armature on the ground it should be laid on clean paper or cloth, but it is better to support it by the shaft on two wooden horses or other supports, and thus avoid any strain on the armature body or commutator.
Fig. 441.—Foundation. It may be made either of concrete, stone or brick. The machinery is held firmly in place on the foundation by anchor bolts built into it; the proper position for the bolts are determined by a wooden template suspended above the foundation as shown. The bolts are surrounded by iron pipe that fixes them vertically but permits a little side play to allow for any slight errors in locating the centers on the template.
Connecting Up Dynamos.—The manner in which the connections of the field magnet coils, brushes, and terminals, are connected to one another depends entirely upon the type of machine. The field magnet shunt coils of shunt and compound wound dynamos, are invariably arranged in series with one another, and then connected as a shunt to the brushes or terminals of the machine. The series coils of series and compound wound machines are arranged either in series or in parallel with one another, according to conditions of operation, and then connected in series to the armature and external circuit.
Coupling Up Field Magnet Coils.—In coupling up the coils of either salient or consequent pole field magnets, assume each of the pole pieces to have a certain polarity (in bipolar dynamos two poles only, a north and south pole respectively, are required; in multipolar dynamos the poles must be arranged in alternate order around the armature, the number of N and S poles being equal), then apply Flemming's rule as given under fig. 132, to each of the coils, and ascertain the direction in which the magnetizing current must flow in each in order to produce the assumed polarity in each of the pole pieces. Having marked these directions on the coils, they can be coupled up in either series or parallel connection according to requirements, so that the current flows in the proper direction in each.
Fig. 442.—Comparison of space occupied by direct and belt connected dynamos. In office buildings space is of value and the room required by belt connected dynamos can always be put to profitable use. For this reason the direct connected unit has become generally adopted in the best type of office buildings. In large factories the direct connected unit is generally adopted also to save space. Where these conditions do not obtain, belted type of dynamo can be used to advantage as a given output can be obtained with a smaller size machine than where it is direct connected to the engine. This is due to the limited rotative speeds at which engines can be run. The illustration shows the relative space required by the two types.
The Drive.—Various means are employed to connect the engine or other prime mover with the dynamo, or the motor with the machinery to driver. Among these may be mentioned the following:
1. Direct drive;
2. Belt drive;
3. Rope drive;
4. Gear drive;
5. Friction drive.