CLASSIFICATION AND NOTATION. 



CLASSIFICATION OF MACHINES.* 



A direct current is a unidirectional current. 



A continuous current is a steady, or non-pulsating, direct 

 current. 



An alternating current is a current of equal half-waves in suc- 

 cessively opposite directions. 



An oscillating current is a current alternating in direction, and 

 of decreasing amplitude. 



Electrical Apparatus will be treated under the following 

 heads : 



I. COMMUTATING MACHINES, which comprise a constant mag- 

 netic field, a closed coil armature, and a multi-segmental com- 

 mutator connected thereto. 



Under this head may be classed the following : Continuous- 

 current generators ; continuous-current motors ; continuous-cur- 

 rent boosters ; motor-generators ; dynamotors ; converters and 

 closed-coil arc machines. 



A booster is a machine inserted in series in a circuit to change 

 its voltage, and may be driven either by an electric motor, or 

 otherwise. In the former case it is a motor-booster. 



A motor-generator is a transforming device consisting of two 

 machines ; a motor and a generator, mechanically connected 

 together. 



A dynamotor is a transforming device combining both motor 

 and generator action in one magnetic field, with two armatures, 

 or with an armature having two separate windings. 



For converters, see III. 



*This classification constitutes a part of the Report of the Committee on Standard- 

 ization, of the American Institute of Electrical Engineers. 



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