The Model Engineer And Practical Electrician Volume 5

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 edition. Excerpt: ... rotation, the beginning of coil i and the end of coil 3 are twisted together (having both been uncovered and cleaned), soldered together, and both then soldered to one of the commutator segments (a) The end of coil 1 and beginning of coil 2, are then similarly treated, and joined to commutator h. End of coil 2 and t eginning of No. 3, are joined to the remaining segment (c). The three coils now practically become a single unbroken wire. The two brushes rest on the commutator at points diametrically opposite, but the position of th's "diameter of commutation" drpends on the position of the commutator segments in relation to the armature coils and also on the position ot the fieldmagnet poles. An approximately correct position i given in the diagram Fie. a. With regard to the field-magnet wind'ng, it is most usual to wind with a separate length of wire for each core. Thus in a bipolar nVld-masnet, with two cores (or winding spaces) as shown in Fig. 2, two equal lengths of wire would be empl, yed. They are wound in a spec il way (for explanation of which see Fig, 4 in the article, '" A Simple Electric Beam Engine " The Model Engineer, May 1st, 1001), in order to produce a north pole at one end and south pole at the other end of the magnet. The connections between the ends of the field-magnet winding and brushes and terminals depends on the question whether the winding is to be in "series " or "shunt." A small motor is usually "series-wound," and in this case, one end of the field-magnet coils is attached to one of the brashes. The other end of field-magnet coils is attached direct to the source of current via one of the terminals T; the second brush being connected to the other terminal Tt....