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CONNECTING AND STARTING

It is possible to connect up this dynamo either as a "Series" or a "Shunt" machine, and diagrams for both are shown, but for all practical purposes the writer advises the shunt connection, as in that case no change in the connections is necessary whether the machine is to be used as a motor or as a generator.

In the diagram for shunt connections, Fig. 61, it will be seen that the center binding post on the connection board is not used.

In the two diagrams for the series connections the center binding post is used and it will be seen that the connecting cable between the brushes and the binding posts of the connection board have to be transposed when the machine is changed from a motor to a generator, and vice versa.

When the machine is to be used as a series motor, the field coils must be connected in parallel by the aid of a second terminal board placed at the rear of the magnet yoke to receive the other ends of the field wires.

To illustrate the various connections clearly they are drawn as though passing out from the brushes and up around the side of the machine, where they turn back again and come to the binding posts on the connection board.

If the cut of the complete machine be examined it

will be readily seen that these connection cables run in a direct line from the brush holders to the binding posts.

The insulated cables furnished with the dynamo parts are longer than the distance between these points, but

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after the connectors are soldered on the cable is given a few turns around a piece of rod about 3/16 inch in diameter, which will form it into a spiral and take up the extra length.

The cables are attached to the connectors by soldering. The insulation is stripped from the ends of the

cable and these ends are soldered onto the projections of the connectors.

One of the connectors is shown in detail in Fig. 31. Before connecting up the brush holders, test them for

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grounds in the same manner that the armature coils are tested.

The brushes should be put in such a position that they will bear on the commutator sufficient to make a good contact at all times.

Three or four pieces of the strip copper should be used for each brush. These will have all the spring

necessary.

After the brush holders are set at the proper position

FIG. 63.-"Series" Connection for Dynamo.

the brass nuts on the brush-holder shanks should be tightened up firmly to keep them there.

A brass connector should be soldered to each of the free ends of the field coils, and these carried to the two end binding posts of the connection board. They should be clamped under the hexagon brass nuts and against the fiber of the connection board as these wires are not dis

turbed in connecting the machine for either shunt or series.

After all the connections have been made, if the machine is to be used as a motor it will, in all probability, start off as soon as current is applied to it.

When used as a generator it will sometimes fail to supply a current when the power is applied. The reason for this is that there is no magnetism in the field to start

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a current when the armature is revolved.. To remedy this use the current from a battery of three or four good cells. Touch the ends of the wires from the battery to the same binding posts to which the circuit wires are attached. This must be done while the armature is being driven at speed.

If the machine does not start off as soon as the battery wires are brought in contact with the binding posts,

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