An elementary book on electricity and magnetism and their applications . me-times it pays to install at the end of the transmission line asynchronous motor which will not supply any mechanicalpower but will just float on the line with its field considerablyoverexcited. Such a machine (Fig. 280) is called a synchronouscondenser, since its effect on the line is exactly equivalent tothat of a condenser. 276. An a-c. series motor. Experience shows that a motor, if the current is reversed, continues to rotate inthe same direction. In fact, almost any small d-c. series motorwill operate o
An elementary book on electricity and magnetism and their applications . me-times it pays to install at the end of the transmission line asynchronous motor which will not supply any mechanicalpower but will just float on the line with its field considerablyoverexcited. Such a machine (Fig. 280) is called a synchronouscondenser, since its effect on the line is exactly equivalent tothat of a condenser. 276. An a-c. series motor. Experience shows that a motor, if the current is reversed, continues to rotate inthe same direction. In fact, almost any small d-c. series motorwill operate on no load if connected to an a-c. line of thesame voltage, but, when a load is put on, it is quite likely tospark badly at the brushes. However, such motors of smallsize are used commercially t<» operate small vacuum cleaners,office appliances, dental engines, and the like. In recent years -, 1 Fig. 280.— Synchronous condenser in substation at Eagle Rock, California,used to improve power factor on a very long transmission line. The ex-citer is in the Fig. 2bl. — Field structure of a single-phase series railway motor. ALTERNATING-CURRENT MOTORS 405 a single-phase series motor with commutator has been de-veloped for railway service to operate on either d-c. or In railway work there is need for a motor with large start-ing torque so that the motor will start under heavy load. Butthe synchronous motor and the induction motor have verylittle starting torque. The series motor is the only alternating-current motor which does have this large starting torque. Inorder to secure the best results from a series motor operatedon alternating current, it is necessary to introduce some specialfeatures. First, since the field coils are excited by an alternat-ing current, it is necessary to have the whole magnetic circuit,including the core and yoke of the field magnets, made oflaminated iron to keep the eddy-current loss small. Thismeans a larger and more expensiv
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
