Principles of Direct-current MachinesMcGraw-Hill Book Company, Incorporated, 1919 - 460 strani |
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Pogosti izrazi in povedi
abamperes abvolts air-gap ampere-turns amperes armature core armature current armature winding battery brush contact coil edges commutator segments conductors connected constant corresponding counter e.m.f. cross-section current density demagnetizing direction of rotation electrical electromotive force element equal equation external circuit field excitation field intensity field resistance field winding flux density full-load hence increase induced iron lap winding length lines of force lines per sq load loss machine magnet pole magnetic circuit magnetic field magnetic potential magnetization curve number of ampere-turns number of poles number of turns ohms pair of poles parallel paths permeance polarity pole cores pole face pole pitch pole shoes pole tips positive reëntrant represents resistance result reversed rheostat ring windings self-inductance separately excited series field shown in Fig shunt shunt field shunt motor simplex slots solenoid speed surface temperature terminal voltage tion torque unit volts wave winding wire y₁
Priljubljeni odlomki
Stran 23 - As a unit of resistance, the international ohm, which is based upon the ohm equal to 10" units of resistance of the CGS system of electromagnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice, 14.4521 grams in mass, of a constant cross-sectional area and of the length of 106.3 centimetres.
Stran 385 - Mica, asbestos and other materials capable of resisting high temperatures, in which any Class A material or binder is used for structural purposes only, and may be destroyed without impairing the insulating or mechanical qualities of the insulation.
Stran 388 - The nominal rating of a railway motor shall be the mechanical output at the car or locomotive axle, measured in kilowatts, which causes a rise of temperature above the surrounding air, by thermometer, not exceeding 90 "C. at the commutator, and 75 °C. at any other normally accessible part after one hour's continuous run at its rated voltage (and frequency in the case of an alternating-current motor) on a stand with the motor covers arranged to secure maximum ventilation without external blower....
Stran 386 - No 1. Thermometer Method. This method consists in the determination of the temperature, by mercury or alcohol thermometers, by resistance thermometers, or by thermocouples, any of these instruments being applied to the hottest accessible part of the completed machine, as distinguished from the thermocouples or resistance coils embedded in the machine as described under Method No.
Stran 354 - Mechanism. The efficiency of a machine is the ratio of the power delivered by the machine to the power received by it. For example, the efficiency of an electric motor is the ratio between the power delivered by the motor to the machinery which it drives, and the power it receives from the generator. Assume, for example, that a motor receives 50 kilowatts from the generator, but that the output of the motor is only...
Stran 195 - percentage regulation" which is the percentage ratio of the change in the quantity occurring between the two loads to the value of the quantity at either one or the other load, taken as the normal value. It is assumed that all parts of the machine affecting the regulation maintain constant temperature between the two loads, and where the influence of temperature is of consequence, a reference temperature of 75°C shall be considered as standard. If change of temperature should occur during- the tests...
Stran ii - Associate Editor, Electric Railway Journal, Formerly Professor of Electrical Engineering, Cornell University. GEORGE W. PATTERSON, Professor of Electrical Engineering, University of Michigan. HARRIS J. RYAN, Professor of Electrical Engineering, Leland Stanford Junior University. ELIHU THOMSON, Consulting Engineer, General Electric Co. WILLIAM D. WEAVER, Formerly Editor, Electrical World. ELECTRICAL MEASUREMENTS BY,
Stran 389 - ... when operated on stand test with motor covers and cooling system, if any, arranged as in service. Inasmuch as the same motor may be operated under different conditions as regards ventilation, it will...
Stran 6 - Force, acceleration, velocity, displacement, momentum, couples, an electric current, are all examples of vector quantities. A vector quantity may be represented by a line, whose length is proportional to the magnitude of the quantity, and whose direction is parallel to the direction of the quantity, the sense or way of action being indicated by an arrow-head placed on the line. The upper line AB (Fig. 1) represents a vector quantity whose magnitude is the...
Stran 13 - Extend the thumb and first two fingers of the left hand at right angles to one another. If the forefinger points in the direction of the magnetic lines of force and the middle finger in the direction of the current in the wire, the thumb will point in the direction of the force on the wire.