Ans. Since the copper loss depends upon the current in the primary and secondary windings, it requires a larger current when the power factor is low than when high, hence the copper losses increase with a lowering of the power factor.
Fig. 1,954.—Method of bringing out the secondary leads in Wagner central station transformers. Each primary lead is brought into the case through a similar bushing. Observe the elimination of all possibility of grounding the cable on the case or core.
Ques. What effect other than heating has resistance in the windings?
Ans. It causes poor regulation.
This is objectionable, especially when incandescent lights are in use, because the voltage fluctuates inversely with load changes, that is, it drops as lamps are turned on and rises as they are turned off, producing disagreeable changes in the brilliancy of the lamps.
Cooling of Transformers.—Owing to the fact that a transformer is a stationary piece of apparatus, not receiving ventilation from moving parts, its efficient cooling becomes a very strong feature of the design, especially in the case of large high pressure transformers. The effective cooling is rendered more difficult because transformers are invariably enclosed in more or less air tight cases, except in very dry situations, where a perforated metal covering may be permitted.
Figs. 1,955 and 1,956.—Westinghouse transformer terminal blocks for high and low tension conductors.