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

Ques. How is the winding of the booster alternator armature connected?

Ans. It is connected in series with the input circuits on the converter.

Fig. 2,063.—Westinghouse 2,000 kw., 270 volt, direct current, 6 phase, 167 R.P.M., synchronous booster rotary converter, having a voltage range from 230 to 310 volts. It consists of a standard rotary converter in combination with a revolving armature alternator mounted on the same shaft with the rotary converter and having the same number of poles. By varying the field excitation of the alternator, the alternating current voltage impressed on the rotary converter can be increased or decreased as desired. The direct current voltage delivered by the converter is thereby varied accordingly. The principle of operation of the booster converter is therefore very simple and easily understood. It is simply a combination of two standard pieces of electrical apparatus, accordingly there are incorporated in it no details of construction essentially different from those encountered in standard rotary converters and alternators. The only novelty is in their combination. The frames may be supported either from the rotary converter frame, as in the small units, or from the bed plate, as in the larger ones. A synchronous booster converter can be built, if necessary, with a vertical shaft to satisfy special floor space and head room requirements.

Ques. How are the field windings connected?

Ans. They are either fed with current regulated by means of a motor operated field circuit rheostat, or joined in series with the commutator leads of the converter.

Fig. 2,064.—Armature of Westinghouse synchronous booster converter. Heavy cast yokes form the frames. They are proportioned to rigidly support the laminated steel field poles. The poles are fastened to the frame with through bolts. A lifting hook is provided on all frames. The bed plates are in one piece for the smaller machines but two piece bed plates are used for the larger ones. The bearings are ring oiling and have babbitt wearing surfaces that are renewable.