Theory and Calculation of Electrical Apparatus (1917) — part 21 of 21

A new type, which offers only a slight advantage in efficiency, size, cost of production or operation, etc., over the existing type, is economically preferable only, if it can entirely supersede the existing type; but if its advantage is limited to certain applica- tions, very often, even usually, the new type is economically inferior, since the disadvantage off producing and operating two different types of apparatus may be greater than the advantage of the new type. Thus a standard type is economically superior and preferable to a special one, even if the latter has some small superiority, unless, and until, the industry has extended so far, that both types can find such Extensive application as to justify the existence of two standard types. This, for instance, was the reason which retarded the introduction of the three-phase trans- former: its advantage was not sufficient to justify the dupli- cation of standards, until three-phase systems had become very numerous and widespread.

In other words, the advantage offered by a new type of appara- tus over existing standard types, must be very material, to economically justify its industrial development.

The error most frequently made in modem engineering is not the undue adherence to standards, but is the reverse. The undue preference of special apparatus, sizes, methods, etc., where standards would be almost as good in their characteristics, and therefore would be economically preferable. It is the most serious economic mistake, to use anything special, where standard can be made to serve satisfactorily, and this mistake is the most frequent in modern electrical engineering, due to the innate individualism of the engineers.

257. However, while existing standard types of apparatus are economically preferable wherever they can be used, it is obvious that with the rapid expansion of the industry, new types of apparatus will be developed, introduced and become standard, to meet new conditions, and for this reason, as stated above, a knowledge of the entire known field of apparatus is necessary to the engineer.

CONCLUSION

475

Most of the less-known and less-used types of apparatus have been discussed in the preceding, and a comprehensive list of them is given in Chapter XXIII, together with their definitions and short characterization.

While electric machines are generally divided into induction machines, synchronous machines and commutating machines, this classification becomes difficult in considering all known apparatus, as many of them fall in two or even all three classes, or are intermediate, or their inclusion in one class depends on the particular definition of this class.

Induction machines consist of a magnetic circuit inductively related, that is, interlinked with two sets of electric circuits, which are movable with regards to each other.

They thus differ from transformers or in general stationary induction apparatus, in that the electric circuits of the latter are stationary with regards to each other and to the magnetic circuit.

In the induction machines, the mechanical work thus is pro- duced — or consumed, in generators — by a disappearance or appearance of electrical energy in the transformation between the two sets of electric circuits, which are movable with regards to each other, and of which one may be called the primary cir- cuit, the other the secondary circuit. The magnetic field of the induction machine inherently must be an alternating field (usually a polyphase rotating field) excited by alternating currents.

Synchronous machines are machines in which the frequency of rotation has a fixed and rigid relation to the frequency of the supply voltage.

Usually the frequency of rotation is the same as the frequency of the supply voltage: in the standard synchronous machine, with direct-current field excitation.

The two frequencies, however, may be different: in the double synchronous generator, the frequency of rotation is twice the frequency of alternation; in the synchronous-induction machine, it is a definite percentage thereof; so also it is in the induction' machine concatenated to a synchronous machine, etc.

Commutating machines are machines having a distributed armature winding connected to a segmental commutator.

They may be direct-current or alternating-current machines.

Unipolar machines are machines in which the induction is produced by the constant rotation of the conductor through a constant and continuous magnetic field.

476

ELECTRICAL APPARATUS

The list of machine types and their definitions, given in Chapter XXIII, shows numerous instances of machines belong- ing into several classes.

The most common of these double types is the converter, or synchronous commutating machine.

Numerous also are the machines which combine induction- machine and synchronous-machine characteristics, as the double synchronous generator, the synchronous-induction motor and generator, etc.

The synchronous-induction machine comprising a polyphase stator and polyphase rotor connected in parallel with the stator through a commutator, is an induction machine, as stator and rotor are inductively related through one alternating magnetic circuit; it is a synchronous machine, as its frequency is definitely fixed by the speed (and ratio of turns of stator and rotor), and it also is a commutating machine.

Thus it is an illustration of the impossibility of a rigid classi- fication of all the machine types.

3324

/

INDEX

Also see alphabetical list of apparatus in Chapter XXIII.

A

Acyclic, see Unipolar.

Adjustable speed polyphase motor, 321, 378

Alexanderson very high frequency inductor alternator, 279

Amplifier, 281

Arc rectifier, 248

Armature reaction of regulating pole converter, 426, 437 of unipolar machine, 457

B

Balancer, phase, 228

Battery charging rectifier, 244

Brush arc machine as quarterphase rectifier, 244, 254

C

Capacity storing energy in phase conversion, 212

Cascade control, see Concatenation.

Coil distribution giving harmonic torque in induction motor, 151

Commutating e.mi. in rectifier, 239 field, singlephase commutator motor, 355, 359

machine, concatenation with in- duction motor, 55, 78 pole machine, 472 poles, singlephase commutator motor, 358

Commutation current, repulsion / motor, 392

series repulsion motor, 400,

404 /

farctor, repulsion motor, 392

Commutation factor of series repul- sion motor, 415 of regulating pole converter, 426, 437

of series repulsion motor, 403 of singlephase commutator motor, 347

Commutator excitation of induction motor, 54, 89 induction generator, 200 leads, singlephase commutator motor, 351

motors, singlephase, 331

Compensated series motor, 372

Compensating winding, singlephase commutator motor, 336, 338

Concatenation of induction motors, 14, 40

Condenser excitation of induction motor secondary, 55, 84 singlephase induction motor, 120

speed control of induction motor, 13, 16

Contact making rectifier, 245

Cumulative oscillation of synchro- nous machine, 299

D ‘

Deep bar rotor of induction motor, 11

Delta connected rectifier, 251

Direct current in induction motor secondary, 54, 67

Disc type of unipolar machine, 454

Dotible squirrel cage induction motor, 29

Double synchronous induction gen- erator, 191, 199, 201

Drum type of unipolar machine, 454

r

478 INDEX

E

Eddy current starting device of in- duction motor, 8 in unipolar machine, 456 Eickemeyer high frequency inductor alternator, 280

F

Flashing of rectifier, 249 Frequency converter, 176

pulsation, effect in induction motor, 131

Full wave rectifier, 245 G

General alternating current motor,

300

Generator regulation affecting induc- tion motor stability, 137

H

Half wave rectifier, 245 Harmonic torque of induction motor,

144

Heyland motor, 92 Higher harmonic torques in induc- tion motor, 144 Homopolar, see Unipolar.

Hunt motor, 49 Hunting, see Surging.

Hysteresis generator, 169 motor, 168

starting device of induction motor, 5

I

Independent phase rectifier, 251 Inductance storing energy in phase conversion, 212

Inductive compensation of single- phase commutator motor, 343

devices starting singlephase in- duction motor, 97, 111

Inductive excitation of singlephase commutator motor, 343 Induction frequency converter, 191 generator, 473

motor inductor frequency con- verter, 284

phase balancer stationary, 228 phase converter, 220 Inductor machines, 274 Interlocking pole type of machine, 286

Internally concatenated induction motor, 41, 49

L

Lead of current produced by lagging field of singlephase com- mutator motor, 366 Leblanc’s rectifier, 256 Load and stability of induction motor, 132

Low frequency exciter of induction generator, 199, 2G3

M

Magneto commutation, 285 inductor machine, 285 Mechanical starting of singlephase induction motor, 96 Mercury arc rectifier, 247 Meter, unipolar, 458 Momentum storing energy in phase conversion, 212 Monocyclic devices, 214

starting singlephase induction motor, 98, 117 Motor converter, 192 Multiple speed induction motor, 14, 20

Multiple squirrel cage induction motor, 11, 27

O

Open circuit rectifier, 237 Over compensation, singlephase com- mutator motor, 418

INDEX

479

P

Permutator, 257

Phase balancer, 228

control by polyphase shunt motor, 324

by commutating machine with lagging field flux, 370 conversion, 212

converter starting singlephase induction motor, 98 splitting devices starting single- phase induction motor, 97,

103

Polyphase excitation of inductor alternator, 283 induction motor, 307 rectifier, 250 series motor, 327 shunt motor, 319

Position angle of brushes affecting converter ratio, 422

Power factor compensation by com- mutator motor, 379 of frequency converter, 178, 184

Pyroelectric speed control of induc- tion motor, 14

Q

Quarterphase rectifier, 251 R

Reaction converter, 264 machine, 260

Rectifier, synchronous, 234

Regulating pole converter, 422

Regulation coefficient of system and induction motor stability, 140

of induction motor, 123

Regulator, voltage-, ’magneto com- mutation, 285

Repulsion motor, 343, 373, 386

starting of singlephase induc- tion motor, 97

Resistance speed control of induc- tion motor, 12

Reversing rectifier, 245 Ring connected rectifier, 251 Rotary terminal singlephase induc- tion motor, 172

S

Secondary excitation of induction motor, 52

Self induction of commutation, 420 Semi-inductor type of machine, 286 Series repulsion motor, 343, 374, 397 Shading coil starting device, 112 Short circuit rectifier, 237 Shunt resistance of rectifier, 235 and series motor starting of singlephase induction motor, 96

Singlephase commutator motor, 331 generation, 212 , 229 induction motor, 93 , 314

self starting by rotary ter- minals, 172 Six-phase rectifier, 253

regulating pole converter, 446 Split pole converter, see Regulating pole converter.

Square, monocycle, 216 Stability coefficient of induction motor, 138

of system containing induc- tion motor, 141

Stability of induction motor and generator regulation, 137 limit of rectifier, 249 and load of induction motor, 132 Stanley inductor alternator, 275 Star connected rectifier, 251 Surging of synchronous machine, 288 Synchronizing induction motor on common rheostat, 159 Synchronous exciter of induction motor, 72

frequency converter, 191 induction generator, 191, 194 induction generator with low frequency exciter, 199, 203 induction motor, 166 as reaction machine, 264

480

INDEX

Synchronous machines, surging, 288 U

motor, concatenation with in- duction motor, 54, 71 Unipolar induction, 452

phase balancer, 228 machines, 450

phase converter, 227 motor meter, 458

rectifier, 234

Tandem control, see Concatenation. Temperature starting device of induction motor, 2 Third harmonic wave controlling converter ratio, 432 Thom son -Houston arc machine as three-phase rectifier, 244, 255

Three-phase rectifier, 251

regulating pole converter, 445 transformer, 472

Transformer, general alternating, 176 Triangle, monocyclic, 216 Triple squirrel cage induction motor,

34

Variable ratio converter, see Regu- lating pole converter.

W

Wave shape affecting converter ratio, 430

harmonics giving induction motor torque, 145 Winter-Eichberg motor, 380

Y

Y connected rectifier, 251