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Shunt and compound winding.
If we drop the outline of the motor, and represent simply the field coils and the armature, then this diagram can be simplified to the form shown in Fig. 3.
In Fig. 4 a diagram of the same type as Fig. 3 is given which shows the connections for a compound wound generator. As will be noticed, the connections with the in
struments and with the field rheostat are the same as for the shunt machine. In this diagram the series coils are connected in successive order, and the armature is at one end, but when the generator is intended to be used singly, the armature can be connected between the series field coils, as in Fig. 5, or as in Fig. 6. In the first
Long and short shunts.
one of these two diagrams, the shunt field coils are connected by the wires e and h directly with the leads from the commutator brushes, so that the coils m m shunt the armature only. This connection is called the short shunt, and is the one most generally used, and, in fact, the only
proper one if close regulation of the voltage is desired. In Feg. 6 the shunt coils lead off from the ends of the series coils, thus shunting these coils as well as the armature. This is called the long shunt.
Sometimes the shunt coils as well as the series are connected, apparently at one side of the armature as One way to avoid.
illustrated in Fig. 7, but on close examination it will be found that the shunt coils straddle the armature, so that the connection is precisely the same as in Fig. 4. In connecting the shunt coils care should be taken that they are not arranged as in Fig. 8, for with this connection
they would shunt the series field coils m m and not the armature.
Multipolar machines of the compound type are connected as in Fig. 9, and in some cases, where the capacity is great, the series coils are placed in parallel, as in Fig. 10. In both these diagrams it will be seen that the voltmeter and the ammeter are connected in the A multi-polar generator.
same way as in the diagrams of two-pole generators, the wires g g connecting with the two mains P and N, and the ammeter being in series in one of the mains. It may
The Derry Collard Co.
be well to mention here that it is immaterial in which one of the lines the ammeter is placed, as the current is the same in both.