Perhaps the transformers were purchased because of their attractive prices and never tested.
Water, plumbing, gas and steam fittings are subjected to test. Why not transformers? Even more so because transformers take constant toll from the company installing them, while gas and water fittings, once passed, are off the contractor's hands.
The busy manager has little time for complicated treatises and monographs on electrical measurements and even handbooks confront him with forbidding formulæ. Accordingly the methods of transformer testing, which are very simple, are illustrated in the accompanying cuts. Managers of electric power and lighting companies should study them carefully.
Fig. 2,015.—Wagner central station core type transformer repair unit consisting of one half set of primary and secondary windings together with the section of the iron core upon which the coils are wound.
An ammeter, voltmeter and wattmeter are required to make the tests. Losses are small in good transformers and hence the instruments should be accurate. For the same reason instruments should be chosen of the proper capacity to give their best readings. If there be any doubt about the testing instruments being correct, they should be calibrated before being used. The testing circuits should be properly fused for the protection of the instruments. It is hardly logical, but a very common practice is to mistrust meters and to watch them closely, while the transformers are guilty of theft unchallenged, and keep busily at it on a large scale.
Fig. 2,016.—Moloney tubular air draft oil filled transformer. The case is made of cast iron, with large steel tubes passing from the bottom through the top. In operation the air in the tubes becomes hot and expands; a draft is thus produced which carries away considerable heat.