ATOCI: HAWKINS ELECTRICAL GUIDE #04 [HEG04]
TABLE OF CONTENTS; GUIDE NO. 4
ALTERNATING CURRENTS 997 to 1,066
The word "ahernating" - advantages of alternating current - direct current apparatus; alternating current apparatus - disadvantages of alternating current - alternating current principles - the sine - application and construction of the sine curve - illustrated definitions: cycle, alternation, amplitude, period, periodicity, frequency commercial frequencies - advantages of low frequency - phase - phase difference - phase displacement - synchronism - "in phase " - curves illustrating "in phase" and `but of phase" illustrated definitions: in phase; in quadrature, current leading; in quadrature, current lagging; in opposition - maximum volts and amperes - average volts and amperes - - elementary alternator developing one average volt - virtual volts and amperes - effective volts and amperes - relatic n between shape of wave and form factor - wave form - - cscillograph wave form records - what determines wave form effectof one coil per phase per pole - single phase current; hydraulic analogy - two phase current; hydraulic analogy - two phase current distribution - three phase current; hydraulic analogy; distribution - inductance - the henry - inductive and non - inductive coils - hydraulic analogy of inductance inductance coil calculations - ohmic value of inductance - capacity: hydraulic analogy the farad specifi inductive capacity - condenser connections - ohmic value of capacity - lag and lead - mechanical analogy of lag - - lag measurement - steam engine analogy of current flow at zero pressure - reactance - examples choking coil - impedance curve - resonance - critical frequencv - skin effect.
ALTERNATING CURRENT DIAGRAMS 1,067 to 1,100
Definitions: impressed pressure, active pressure, self - induction pressure, reverse pressure of self - induction rate of change in current strength - properties of right angle triangles - equations of the right triangle - representation of forces by wires - parallelogram of forces; the resultant - circuits containing resistance and inductance - graphical method of obtaining the impressed pressure - equations for ohmic drop and reactance drop - examples - diagram for impedance, angle of lag, etc. - circuits containing resistance and capacity capacity in series, and in parallel - amount of lead action of condenser - the condenser pressure - capacity pressure - equation for impedance - examples and diagrams - circuits containing resistance, inductance, and capacity - impedance equation - examples and diagrams - equation for impressed pressure - examples and diagrams.
THE POWER FACTOR - 1,101 to 1,124
Definition of power factor - true watts - apparent watts - ferry boat analogy of power factor - limits o_ power factor - effect of lag or lead - how to obtain the power curve - nature of the power curve - synchronism of current and pressure; power factor unity - case of synchronism of current and pressure with power factor less than unity steam engine analogy of power factor "wattless current"; power factor zero - examples of phase difference nearly 90 degrees - mechanical analogy of wattless current why the power factor is equal to cos 0 - graphical method of obtaining the active component - examples and diagrams - effect of capacity - diagrams illustrating why the power factor is unity when there is no resultant reactance in the circuit usual value of power factor power factor test - how alternators are rated; kva. - curves illustrating power factor - how to keep the power factor high - why power factor is important in station operation - wattmeter method of three phase power measurement.
ALTERNATORS 1,125 to 1,186
Uses of alternators classes of alternator single phase alternators; essential features: width of armature coils elementary single phase alternator - polyphase alternators - uses for two and three phase current - elementary three phase alternator starting difficulty with single phase motors - six and twelve phase windings - belt or chain driven alternators - sub - base and ratchet device for tightening the belt - horse power transmitted by belts best speeds for belts advantages of chain drive; objections - direct connected alternator - "direct connected" and "direct coupled" units - revolving armature alternators; their uses - revolving field alternators - marine view showing that motion is purely a relative matter essential parts of revolving field alternator - the terms "stator" and "rotor" - inductor alternators: classes, use, defects - hunting or surging in alternators - amortisseur windings - monocyclic alternators - diagram of connections - teaser coil - armature reaction distortion of field - strengthening and weakening effects - superpositions of fields - three phase reactions - magnetic leakage - field excitation of alternators - self - excited alternator - direct connected exciter - gear driven exciters - slow speed alternators - fly wheel alternators - high speed alternators - water wheel alternators - construction of rotor - turbine driven alternators - construction - step bearing - alternators of exceptional character - asynchronous alternators image current alternators - extra high frequency alternators self - exciting image current alternators.
CONSTRUCTION OF ALTERNATORS - 1,187 to 1,266
Essential parts of an alternator - field magnets - methods of excitation: self - excited, separately excited, compositely excited - magneto - construction of stationary magnets - revolving field - slip rings - spider for large alternator - provision for shifting armature to give access to field - armatures - core construction - advantages of slotted core armatures - armature windings classification: revolving and stationary windings - half coil and whole coil windings - concentrated or uni - coil winding; features; wave form - distributed or multi - coil windings: breadth of coil, partial and fully distributed coils - the Kapp coefficient - general equation for volt - age - wire, strap, and bar windings - condition, governing type of inductor - coil covering - single and double laver multi - wire inductors and methods of placing them on the core - insulation - core stamping - single and multi - slot windings - arrangement in slot of two layer bar winding - table of relative effectiveness of windings single phase windings - advantage of half coil winding two phase windings - shape of coil ends - three phase windings - shape of coil ends - kind of coil used with three phase windings - grouping of phases - two phase star connection two phase mesh connection three phase star connection - winding diagrams with star and p connections - three phase A connection - three phase winding with "short" coils three phase lap winding star connection - three phase wave winding star connection - output of star and delta connected alternators - gramme ring armatures showing three phase star and mesh connections with direction of currents in the coils features of star connection - characteristics of delta connection - proper ends to connect to star point - determination of path and value of currents in delta connection - points to be noted with Y connection - diagram of Y connection with return wire - chain or basket winding skew winding - fed - in winding - imbricated winding spiral winding - mummified winding - shuttle winding creeping winding - turbine alternator winding: how the high voltage is obtained with so few poles; table of frequency and revolutions - turbine alternator - construction - form of armature generally used - two pole radial slot field - parallel slot field - difficulty experienced with revolving armatures - how the field design is modified to reduce centrifugal force - examples of revolving fields.