Design of Direct-current Machines ; Design of Transformers ; Design of Alternating-current Machines

International Textbook Company, 1916 - Electric machinery

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Page 20 - The induced electromotive force in an armature coil is proportional to the rate of change in the number of lines of ArmatureA.
Page 6 - The efficiency of a generator or motor is usually expressed in percentage, and is the ratio of the power output to the power input. The power input is the sum of the power output and the losses.
Page 31 - ... of the pediment. The height of a pediment is determined as follows. In Fig. 20 let A be the point in which the axis of the pediment intersects the highest line of the horizontal cornice. With this point as a center and with a radius equal to one-half the width of the pediment, draw a semi-circle below the pediment as shown in the figure. This IONIC - ORDER ELEVATION- -SECTION ARCHED - DOORWAY PLATE XXII.
Page 62 - ... the force with which the balls of this electrometer endeavoured to close when the wires were inserted bore to that with which they endeavoured to close without [A the wires was thus found. The weight of the straw...
Page 31 - With this point as a center and with a radius equal to one-half the width of the pediment, draw a semi-circle below the pediment as shown in the figure. This LEVATION- -SECTION 2 In. 41 -ARCHED - DOORWAY PLATE XXII. semi-circle intersects the axis of the pediment at the point B. With B as a center and with a radius equal to the distance from B to C (the extreme outside point of the horizontal cornice) draw an arc above the cornice. The point D, in which this arc intersects the axis, will be the highest...
Page 115 - If the permeability of the iron n is sufficiently high, almost all the reluctance of the magnetic circuit is in the air gap and li/tia* is very small relative to La,,, Equation 2 then reduces to L = X 3.19AT" X 10-" (3) The expression a,/la is called the permeance of the air gap.
Page 13 - The effectiveness of armature reaction in weakening the field is proportional to the sine of the angle by which the current lags behind the impressed pressure.
Page 153 - This difference is due to the fact that the current in the armature winding of a synchronous converter at any instant is the difference between the instantaneous values of the alternating current and the direct current.
Page 9 - The magnetic effects of the short-circuited currents in a motor armature assist the field excitation and these may amount to from 5 per cent. to 10 per cent. of the armature reaction.