Fig. 2,043.—Westinghouse rotary converter armature spider. It is made of cast iron or cast steel. The dovetail grooves are machined in the feet or ends of the arms and in these slots the laminations forming the armature coil engage.
Ques. Does variation of the field strength materially affect the voltage?
Ans. No.
Since variation of the field strength does not materially affect the voltage, by adjusting the resistance in series with the magnetic circuit, the strength of the field can be changed and the power factor kept 1 or nearly 1 as different loads are thrown on and off the rotary.
Ques. What is the effect of a field too strong or too weak?
Ans. If too strong, a leading current is produced, and if too weak, the current lags, both of which reduce the power factor and are objectionable.
Usually there is a power factor meter connected up in the main generating station and one also in the rotary substation, and it is the duty of the attendant at the substation to maintain the proper power factor.
Ques. What is the ordinary range of sizes of rotaries?
Ans. From 3 kw. to 3,000 kw.