[Engraving: Test Instrument: original size (4K) | 9x enlarged (25K)]
The success or failure of any machine is definitely determined when it has been in operation for a term of years, but the manufacturer, with a reputation to uphold, and the purchaser, with exacting requirements to be fulfilled under heavy penalty for failure, cannot wait for time's derision. Before any part of the product takes its place in the machinery of industry, the manufacturer and purchaser want positive assurance that there will be no failure and no disappointment. Such assurance can be obtained only by reproducing the conditions of actual service and giving every appliance a thorough test. To conduct such tests is manifestly impossible without a vast amount of available power and an expensive equipment of appliances and experienced men, such as cannot he maintained except in connection with a works large enough to insure their constant employment. The Testing Department at the Schenectady Works occupies all of one large building (No. 11) and large spaces in several others. When any machine is set up and connected for test, calibrated instruments are secured from the Standardizing Laboratory. All readings of the test are set down on a record sheet provided for the purpose, and forwarded to the calculating room in the Testing Department offices. Here the calibration curve of each instrument is applied and corrected readings are entered in a parallel column on the sheet. The results of all tests are forwarded to the Engineering Department for approval or comments.
[Photo: Main Floor of Testing Department (Building No. 11): original size (31K) | 4x enlarged (103K)]
Steam power for driving large generators and steam for testing turbines and direct connected marine engine-generator sets are provided. The principal source of the electric power used in the Testing Department is a 1200 Kw. direct current machine, which is direct connected to a 1500 H.P. tandem compound engine. This generator has two commutators and two separate armature windings, so that 250 or 500 volts may be obtained. For general use the commutators are connected in series, thus giving from 500 to 600 volts. Feeders from this machine are brought out to the main switchboard provided with suitable circuit breakers and switches and from there distributed to the switchboards in the various tests. Each of these switchboards has its own circuit breakers and switches, so that in case a short circuit occurs in a section it will not necessarily shut down the entire department. All of the shop motors in the department are run from this circuit also. In addition the department is equipped with a 250 volt three-wire system from which power may be taken at either 250 or 125 volts. This circuit is obtained from the double commutator rotary converters in the Power Station.
In the center of the annex building, a bank of generators constituting the exciter plant run continuously. The fields of all exciters and the armatures are brought to one board so that they may be excited from any voltage and the armatures connected to any part of the department where an exciter is required.
The general method of testing all generators is to belt them to motors of sufficient capacity to drive the generator at its full load. This load is obtained in various ways: by absorbing the power in water rheostats. by pumping it back into the driving circuit and thus supplying only the losses. etc.
[Photo: A View in the Testing Department: original size (24K) | 4x enlarged (77K)]
The large steam engine in Building No. 12 is used in tests of generators up to 1000 Kw. Not infrequently a direct current generator is assembled in the pit and direct connected to the engine while two motors are belted to the engine, one on either side of the large fly-wheel. By this plan the engine supplies only the losses and a 600 Kw. generator may be tested by belting two 300 Kw. machines on either side of the fly-wheel and driving them as motors from the generator in the pit.
In the Railway Motor Test, motors of the box type are also operated under load by this "pumping back" method, and owing to the severe usage which railway motors are likely to receive, the tests are unusually thorough.
[Photo: Making Simultaneous Readings, Testing Department: original size (12K) | 9x enlarged (83K)]
An interesting feature of the Induction Motor Test is the measurement of slip by the arc lamp method. On the shaft of many of the motors in test will be seen a disk which has as many black and white sectors as there arc poles on the motor. The arc lamp is operated from the alternating current generator which drives the motor. When the disk is rotating with the motor and observed by the light of this arc lamp, the black sectors appear to be slipping backward, because of the difference in speed of the motor and generator. In this test the tables and the arrangement of switches for reading current in all legs by means of one meter only are also of interest.
In general, the tests applied to all lines of apparatus are of far greater severity than the apparatus will be likely to meet in its commercial use, and in case any special guarantees are made as to tcmperature rise, or overload runs, the Testing Department is always very particular to see that the machines fully meet these guarantees.
The working force of this department is chosen with great care and includes representatives of nearly all of the leading technical schools of the world. At the present time the 575 men employed in the testing force include graduates of 67 colleges and universities of 18 different nations. Nearly every civilized country in the world is from time to time represented in this remarkable force of experts. A man is seldom allowed to stay permanently in any one department, but after being thoroughly trained is passed along to another where under experienced guidance he becomes a specialist for the time being, and is then transferred again for further training. The Testing Department thus has a double value in that it provides for tests by very high grade men, and also provides properly equipped men for important positions in the Company's Engineering and Commercial Departments.
[Engraving: Worker inspecting machine with a lamp: original size (6K) | 9x enlarged (35K)]
