Hawkins Electrical Guide v. 06 (of 10) / Questions, Answers, & Illustrations, A progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications

by N. Hawkins

• S_f = Synchronous speed, or R.P.M. of the rotatory magnetic field;
• S_a = Speed of the armature.

The synchronous speed is determined the same as for synchronous motor by use of the following formula:

		2f
Sf	=
		P

where

• S_f = Synchronous speed or R.P.M. of the rotating magnetic field;
• P = Number of poles;
• f = frequency.

Fig. 1720.—Triumph back geared polyphase induction motor. A great many applications, especially for direct attachment, require the use of either a very slow or special speed motor. As these are quite costly, the preferable arrangement, and one equally as satisfactory, is the use of a standard speed motor combined with a back geared attachment. Rawhide pinions are furnished whenever possible, insuring smooth running with a minimum of noise.

Figs. 1,721 to 1,735.—Parts of General Electric small polyphase induction motors. A, armature; B, key for armature shaft; C, oil ring; D, bearing lining; E, bearing head, pulley end; F, cap screw for bearing heads; G, field, complete with winding, terminal plate and leads; H, motor leads; I, terminal connector for motor leads; J, soft rubber bushing for motor leads; K, terminal plate; L, screw for terminal board; M, field coils; N, wooden top sticks for field coils; O, oil filler; P, bearing head opposite pulley end; Q, screw for oil well cover; R, oil well cover; S, socket pipe plug for bearing head; U, motor base; V, yoke for motor base; W, motor base adjusting screw; X, bolt for motor base and frame (short); Y, cap screw for bearing head; Z, internal directive fan; Aa, pulley.