The windings must be carefully made and every care taken to see that they are properly insulated. It is a very good plan to insert a layer of paper between each two layers of wire.
After the windings are finished they are ready to assemble on the core. In order to put them in place, the core must be taken apart first. The primary and secondary go along side of each other on the centre tongue of the A strips.
The core is put together again with the windings in position by slipping each alternate "A" strip through from the opposite direction so that when it is all assembled the result is like that shown in Figure 62.
The transformer is now ready for mounting. The usual method of mounting a step-down transformer is to place it in an iron box or case. This is of course the best way because the windings and core are then protected. The experimenter who wishes to go to the trouble of building an iron box for his transformer will find it worth the time.
For the benefit of those however who may wish to mount the transformer on a switchboard or as part of some apparatus, the scheme shown in Figure 63 is suggested. The base consists simply of a rectangular piece of hardwood which has been given a coat of shellac.
[Illustration: FIG. 63.—The Step-down Transformer mounted on a Wooden
Base.]
The transformer core rests on two wooden strips marked "S" and "S" in the illustration. It is clamped to the base by two strips, "T" and "T," held in position by round head wood screws at each end.
The terminals of the primary winding are led to the two binding posts, marked "P" "P." The secondary terminals are connected to three binding posts, marked 1, 2 and 3.
The 110 volt A. C is connected to the primary posts P P by means of a flexible wire and plug which can be screwed into the nearest lamp socket.
The low voltage is secured from the binding posts 1, 2 and 3.