| Popis: |
The statement is frequently made that 25-cycle alternators are more expensive than 60-cycle machines built for the same output, speed, voltage, and phase. A considerable difference of opinion exists at the present time as to how much more the low-frequency machine should cost than the corresponding high-frequency machine. When an attempt is made to analyze conditions, by examining the cost records of machines built by a large manufacturing company, one is confronted by a maze of figures which assist but little toward solving the problem. This is not at all surprising when one considers the many changes which have accompanied the rapid development of alternating-current generators. Some machines have a relatively great amount of iron, while others have a relatively great amount of copper; there is considerable difference in the results obtained from the various methods used for ventilating alternators; some are much more liberal as regards heating, or voltage margin, or regulation, than others; the excitation differs appreciably in machines for nearly the same rating; some were built when material and labor were high, etc. In this paper an attempt has been made to eliminate, as far as possible, some of these variables. |
