None
In this case the pressure is radial on the commutator and evenly distributed over the whole of the brush surface, so that the wear is also evenly distributed. In brush holders of the types (1) and (2) above, the wear is greatest at the edge of the brush nearest the spring or the brush spindle. Furthermore in types (3) and (4) the brush itself is free to move as it wears, and there are no other parts of the brush mechanism rigidly connected to it. In designs where the brush is left free in this way, the moving parts have the smallest inertia, and respond more readily to variations in the truth of the commutator. 494 BRUSHES AND BRUSH GEAR. c^^p-4i Fig. 354. — Section of the Moi^an Crucible Company's pneumatic brush holder. Fig. 353. — Morgan Crucible Company's spring brush holder for high speeds. PNEUMATIC BRUSH HOLDERS. 495 The above discussion relates to brush holders in which the pressure is obtained by means of a spring. Another example which varies considerably in constructional detail, but is based on the same general principles as the above, is illustrated in Fig. 353. For a more detailed analysis of the design of brush holders, ref- erence should be made to some of the standard works on Dynamo Design. It should be mentioned, however, that most of the diffi- culties generally discussed in these treatises are greatly intensified in high speed machines. As an example of a brush holder designed for peripheral speeds up to 40 metres per second. Fig. 353 shows a type employed by the Morgan Crucible Company. The brush holders are mounted on a rod of D section, and a similar rod conveys the current from the flexible connectors. The pressure is obtained from a spring, as shown, and is conveyed by means of links, which produce a parallel motion for the brush. In a more elaborate design by the same firm, the pressure is obtained by means of compressed air, which provides a very flexible method of adjusting the pressure on the brushes, and avoids the difficulty of the pressure altering as the brush wears away. A section of the cylinder is shown in Fig. 354. The compressed air is led through a series of channels to the rubber bag K, and exerts a downward pressure on the plunger F; this pressure is transmitted by a close wound steel spring G to an ebonite nipple H which is spherically shaped at the lower end, to bed into the top of the carbon brush as shown in Fig. 355. The rubber bag K is coated with silk and is provided with a sealing valve to isolate the holder in the event of the bursting of the bag. This is obtained by the action of the rubber diaphragm between the washer L and the plug M) the normal path for the air is through a channel or groove in the plug /, past the brass washer L and the rubber diaphragm, through a similar channel in the plug Jlf , and finally through the small hole to the bore of the plug, whence it has easy access to the interior of the rubber bag. The rubber diaphragm, being subject to equal pressures on each side, will remain flat, as shown in the drawing. If, however, the rubber bag bursts, the difference in pressure between the two sides of the dia- phragm causes it to bulge downwards, and this at once closes the small hole in the plug M. The effect of this valve is to automatically cut oflf the supply of 496 BRUSHES AND RUSH GEAR. Fig. 355. — Moiigan Crucible Company's pneumatic brush holder. BRUSH HOLDERS. 497 air to a holder as soon as the bursting of the bag produces this differ- ence of pressure. The plunger F also contains a groove (not shown in the figure) which by means of a screw in the cylinder E provides a stop to limit the travel of the plunger. Fig. 355 shows this type of brush holder fitted to a grooved com- mutator, which is a device that has often been tried with the object of avoiding excessively long commutators. It is very doubtful, how- ever, whether it is good practice to use these grooved commutators. While they reduce the first cost of the machines, it is doubtful whether they commutate so successfully as smooth commutators. Pneumatic brush holders have, no doubt, several advantages, but it should be remembered that a further source of breakdown is intro- duced; and though breakdowns to the pneumatic plant may be im- probable, yet when they do occur the generator is put completely out of action. It occurs to us, however, that such a holder might be provided with springs in case of such emergency, the springs being out of action so long as the pneumatic pressure is in working order. INDEX. By E. S. Walpole. Note: The figures throughout refer solely to the pages of the book, and not to the numbers assigned to the different illustrations or tables. A. Active Material, see Material, Effective. Acyclic Generators, see Homopolar under title Continuous Current Machinery. Air Gap: Ampere Turns, see Armature Ampere Turns. Depth — Armature strength, flux and number of poles, relation between for 3000 kva. alternators at various speeds 175-178 Calculation for: 30 alternators of various speeds and ratings 100, 101 400 kva. alternators 134, 142, 143 650 kva. alternators 121 6000 kva. alternators 208, fig. 207 Comparison between 1500, 3000 and 6000 kva. alternators . . 216, fi^. 215 Regulation and relation between 81-87, fi>gs. and table Diameter — Determination for 300O kva. alternators 157, 168 Output coefficient and, Relation between 11 Speed, Influence of 13, 106, figs. 104, 105 Weight coefficient and, Relation between 19, fig. IS AUgemeine Elektricitats Gesellschaft: Alternator with open frame fig. 220 Continuous current machines 450-454 Rotating field structures 260, 261 and figs. Water cooled turbo-alternator 227, fig. 230 Alternating current machinery 65 et seq Armature core plates, Low loss sheets for 45, 47-52, 57 Bipolar alternators 93, 131 e^ seq, 157 Armature core plates, Low loss sheets for 50, 57, table 58, 183 Data and comparison of 1500 R.P.M., 2 pole, and 750 R.P.M., 4 pole designs 181-184 Data for certain designs 146 Pressure regulation 80, 183 400 kva. machine 141-143 500 kva. machine 14d-152 499 600 INDEX. Alternating current machinery. — Continued. Rotating armature: Advantages 152-155 Specification and outline drawings, Comparison between rotating field and 131-137, 152-155 Armature core plates, Effect of grade on cost and quality . . . 49-52 Discussion on 138 Rotating field 249 et seq Smooth drum type 258 Specification and outline drawings, Comparison between rotating arma- ture and 131-137, 152-155 Test results on Westinghouse 500 kva. machine 146-152 Ventilation of rotor 141, 146 Weight and cost ' 137, 142-145 Whole-coiled windings for 243 400 kva. machines, specification and outline drawings 133-137 Discussion 137-155 Laminations, ordinary grade and special low loss iron: Comparison between 57, UAle 58 Effect of grade on cost and quality 49-52 Chief considerations 88 Construction of high speed alternators 219 et 8eq Armature windings for turbo-alternators 228-246 Methods of retaining end windings 241-243, 245 and figa. Rotating armature and field systems, see those titles. Stator frames 219-228, /i^^a. 219-230 Ventilation 219 et seq Design of 1000 kw., 6 phase turbo-alternator for use with rotaiy converter, 204-411 Excitation regulation 404, 407-411 Efficiency, A.I.E.E. Standardization rules 149 Excitation data for 6000-kva., 3-phafie, 6-pole, 37.5-cycle, 750-R.P.M. alter- nator 82-87, figs, and table, 200 General considerations relating to the influence of the rated output and speed on design 88 et seq General procedure in alternator design 103 et seq Output coefficient ^ as a basis for 103 650 kva., 4-pole alternator, design of 107 Armature core plates: Depth 118 Special low loss iron for 53 Armature reactions and regulation, calculation 127 Armature slot 117, fig. 118 Determination of principal dimensions 108 Field excitation at no load, calculations 122 Outline drawings 126, 127 Outline sketch of field 114 Rotating field 113,114 Stress calculations in alternative construction 305-310 Saturation curve 123 Specification 127 INDEX. 601 Alternating current machinery. — Continued. 1500 kva. alternator: Comparison with 3000 and 6000 kva. machines 214-217 Outline drawing and specification 210-214 6000 kva., 4, 6 and 8-pole designs for different frequencies .... 197 et seq Comparison with 1500 and 3000 kva. machines 209-217 Discussion 205-208 Excitation data S2-S7 table and figs. Outline drawings, 198 — for 8-pole machine 210 Saturation curves 199-201 Specifications, 201-204 — for 8-pole machine 211-214 3000 kva. alternators for various speeds and numbers of poles, develop- ment 156-168 25-cycle designs: Armature core plates, effect of grade 47-49, 183 Specification and outline drawings for 3-phase, 11,000 volt designs 168-170 Speed, Discussion of influence on 170 et seq Weights and costs of effective material 170, 17S et seq 1500-R.P.M., 2-pole and 750-R.P.M., 4-pole designs, data and com- parison 181-184 50-cycle designs: Pressure regulation 71 et seq Specification and outline drawings for 11,000 volt designs, 184-187, 210-214 Speed, Influence of 188 et seq Weights and costs of effective material 187, 190 et seq Comparison of 25- and 50-cycle machines 184-196 Comparison with 1500 kva. and 6000 kva. designs 210-217 Slots and teeth. Determination of 165 Heating coefficients for several generators 35; tables^ 33, 34; fi^. 32 High 17. Low Speed Generator, see Low v. High Speed Generator. Leading data for 30 alternators 99-102 Low and high speed generator: Pressure regulation 90 Specifications and comparison 95-99, fig. 94 Temperature rise 89 Magnetic flux per pole 91 Output coefficients 10-14 Inter-relation of 7 Polyphase machines: Output coefficient: Air gap diameter, relation between, 11 — Influence of speed 13, 106, figs. 104, 105 Rated output, Relation between, 10 — Influence of speed 12 Weight coefficient and air gap diameter. Relation between .... 19, /i^. 18 Weight coefficients of several alternators tdUe 20 Pressure regulation 65 et seq Additional ampere turns 66-77 Demagnetising 66-74, 78 Magnetic leakage. Turns for increased 76, 78 Reactance voltage. Turns required for 74->76 602 INDEX. Alternating current machinery. — CanHnued. Effect of on ff and ^ 9, 15 High V, low speed altematoiB 90 Rotating annature and field syBtems, see those titles. Speed and number of poles, Influence on: 400 kva. alternators 131 et seq 3000 kva. alternators 156 et seq High speeds, Development of 1 Designs for 6000 kva. and study of laige designs in general .... 197 et 9eq Most appcopriate for A. C. Machineiy 4, 218, 324 Behiend's curve 95 Stresses in rotating field systems 126, 305 et 9eq Temperature rise 28 Influence of rated speed on 88-90 Thermal calculations 2Sel aeq Turbo-alternators, Examples of 276 et seq British Thomson-Houston Company 284-294 Brown Boveri and Ck)mpany 283 Heyland self-compounding 2-pole machines 301-303 Rotating armature and field. Comparison 304 Oerlikon Company . 276-283 Scott and Moimtain 295-301 Ventilation ooeflicient: Determination of 39 Method of calculation and use 40 Voltage coefficient 7,9, 14, fig. 112 Water wheel generators, Field construction for 272 Weight coefficients 6, 18-24 400-kva., 60-cycle alternators: Armature core plates, Effect of grade on cost and quality 49-52 Specifications and outline drawings 133-137 Speed and number of poles. Influence on designs 131 et seq Ampere turns, see Armature ampere turns. Angle brackets for retaining field coib 267, fi^f. 26 Stresses in 309 Angle of lag. Internal, in large turbo-alternators 92 Angular speed, see Speeds, angular. Arm type spring pressure brush holder 489 and fig. Armature: Ampere turns: Additional field: Demagnetizing component, 66-74, 78 — Relative magnitude 91 Magnetic leakage, A. T.'s for increased 66, 76, 78, 91 Reactance voltage, Turns required for 66, 74-76, 91 Distorting component 73, 78 Field turns: Air gap in 650 kva. alternators 121 Iron, Ratio of to air gap A. T.'s 80 Per cm. of periphery, Influence of value on reactance voltage of C. C. machines, noU 337, 338-^42 Per pole(ni), see Armature strength. INDEX. 608 Armature. — ConHnued. Body: ^ 650 kva. alternator 119 1000 kw. C. C. generator, Stress calciilations 461 Thermal calculations 30 Conductors, see that title. Core, External diameter for 3000 kva. alternators 167 Core plates 45 Brown Boveri C. C. turbo-dynamo 426 Cost 57 Customary dimensions 53 Depth of, in 650 kva. alternator 118 Epstein method of testing 52 Figure of loss 53-57 Oerlikon rotating fields 255 Permeability, Saturation curves showing 59 Special low loss sheet iron for ^5 et seq Cost 57 Figure of loss • 55, 56 Weight, Reduction in, Advantages of rotating armature .« 154 750 kw., 250-volt, 1500-R.P.M. C. C. generator 443 Diameter and output coefficient. Relation between for C. C. machines ... 15 Dimensions [D^ Xg] : Dependent on a and p, 9, 17 Jlated speed. Relation between, for 3000 kva. alternators for different speeds 170, 171,188 Weight coefficient. Relation between 22 et seq Distortion in C. C. Machines, Neutralizing 418 Heating coefficients, see Heating coefficients. Inductance calculations for 650 kva. alternators 123 Interference, see Reactance Voltage. Iron Loss, eee Losses. Laminations, see Armature Core Plates. Losses, see Losses. Ratio of diameter to core length -r- for 30 alternators of various speeds and outputs 100, 101 Reactions and regulation. Calculations for 650 kva. alternator .... 123-125 Rotating, see that title. Specific Magnetic and Electric Loading, see Specific Utilization Coefficients. Stampings, see Armature Core Plates. Stationary, Specific temperature rise of field coils 41, 43 Strength (ni): Air gap depth. Flux and number of poles. Relation between for 300 kva. alternators for various speeds 175-178 and figs. Calculation, 67 — for 650 kva. alternator 115 Comparison between 1500, 3000 and 6000 kva. alternators . . . 216, figs. 215 Reactance voltage, Relation between in C. C. machines 336 et seq 6000 kva. alternators 208, fig, 207 Strong and weak 80 Temperature rise, Methods of estimating 27 et seq 604 INDEX. Armature. — Continued. Turns and flux for 3000 kva. alternators 158, 159 Ventilated revolving armatures, Thermal calculations 28 Windings for turbo-alternators, see Windings, A. C. Austrian Union Company, Method of reducing stresses in end connections . . 421 Auxiliary commutating poles of 750-kw., 250- volt, 1500-R.P.M., C. C. gener- ator, 443 Axial type Homopolar Generator, Me Continuous Current Machinery. B. Bailey &. Cleghome brush contact resistance investigations 480 Balancing 275 Bar Windings, see Windings, A. C. Barrel Windings, see Windings, A. C. Barrel wound armatures, Hermal calculations of continuous current .... 28 Basket winding 240 Behrend : Curve showing comparative weights of 1000 kva. 25-cycle alternators at different rated speeds 93, 95 Comparison with weights of 400 kva. alternators 143 Comparison with weights of 3000 kva. 25-cycle alternators .... 180, 181 Beyer, Data of 375 kva. British Westinghouse Company's C. C. turbo-generator, 448 Bipolar Alternators, ^e A. C. Machinery. Box type spring pressure brush holder 489 and fig. Breadth factor 67 British Engineering Standards Committee, Inherent regulation recommendar tions 65 British Thomson-Houston Company: Definite pole rotor construction 266, fijg. 265 Method of retaining field coils 267, figs. 264, 266 Stress calculations 309 Stator frame. Section of open type 221 3-phase, 1500 kva., 11,000 volt, 6-pole, 50-cycle, 1000 R.P.M. alternator, 284-294 No load saturation curve 294 Outline drawings 94 Pressure regulation 90 Principal dimensions 291 Rotating field for 287, figs. 288, 291, 312 Specification 95-98 Stress calculations 310-318 Temperature rise, Data 89 Test report, Data 293 Winding diagram, 240; fi^s. 238, 239, — Method of retaining end windings, 242, fi^s. 240 British Westinghouse Company: 200 kw., 2000 R.P.M., 110 volt, C.C. dynamo 446,^.447 375 kw., 2500 R.P.M., 250 volt, C. C. turbo-generator field 445, fi^. 446 Specification 448-450 Bronskohl Brushes, see Brushes, Compound. INDEX. 605 Brown Boveri A Oonipany: Annatuie windings 244-246 and fig8. Bipolar altematorsy Data of 146 C. C. turbo-generators description 426-435 Particulars of 4-pole, 1000 kw., 550 volt, 1250 R.P.M. machines . . . 431-435 Brush gear for 434, 486 Standardization of 283, 436, 437 Rotating field constructions 249, 250, fig8, 248, 250 Ventilating scheme for turbo-generator 224 Turbo-alternators development of 283 1000 kva., 1500 R.P.M., 2000 volt, d-phase machine: Outline drawing facing 284 Ventilating scheme 224 Ventilating arrangements 222, 284, fig. 224 Brown, C. E. L., see Brown Boveri A Co. * Bruce, Peebles & Co.: Rotating field structure 267 Winding of bipolar armature 244 Brush Company commutator segments, Method of interiocking 423 Brush Contact Resistance, see Contact Resistance. Friction Loss, see Losses, Commutator. Pressure 487-495 Brushes and brush gear for high speed continuous current dynamos . . 468 et seq Brown Boveri's C. C. turbo-generators 427 4-pole, 1000 kw., 650 volt, 1250 R.P.M. machine . . .* 434,486 Carbon: Choice of 478 Commutator loss involved by use of, in high speed machines 412 Copper commutators 326, 327 Flexible connector or "pigtail", methods of attaching . . . 487-491 and figs. General properties of 471 Graphite, 469 — advantages for high speed machines 412, 415 Le Carbone Company: Graphite method of converting carbon into 479 Pigtail method of attaching . . , 491 "X" and "Z" grades 473,474 Manufacture of 478-480 Metal and. Relative advantages and disadvantages 468-471, 481 Quality and contact resistance 474 Speeds of A. E. G. C. C. turbo-generators employing 454 Compound 481-487 Advantages 412 Bronskohl 487 Burleigh's construction 482 "Endruweifor Galvano 483 Laminated 482 Moiganite 483-485 Brush holders 494-497 Method of attaching "pigtail" 489 National Carbon Company 482 Method of attaching pigtail 489 606 INDEX. Brushes and brush gear for high speed continuous current dynamos. — Ccmtttiiiai. Hlot 485 Use of, in high speed machines 412 Copper and peripheral speeds 327 Holders 487-i97 Design and adjustment 478 Pneumatic 495-497 Spring pressure 487^95 Arm or lever type 491 and fig. Box type 491 cmd fig. Reaction type 491, 493 and fig. Spring arm type 491 and fi/g. Improvements for high speed machines 412 Metal: Carbon and, relative advantages and disadvantages 468-471| 481 Speeds of A. E. G. C. C. turbo-generators with 452 750 kw., 250 volt, 1500 R.P.M., C. C. generator 443 Bullock Company, Rotating field structures 261, fig. 263 Burke, James F., Methods of interlocking commutator segments 423 Burleigh's construction for compound brushes 482 C. Carbon Brushes, see Brushes. Cast iron, Saturation curves showing permeability 59 Cast steel, Permeability and magnetic properties 58, 59 Ceylon graphite for Morganite brushes 485 Coil Winding, see Winding, A. C. Coils: Concentration and distribution of 230 Designation, etc 230 Lap 231,^.230 Method of treatment 287 Spiral 231, /Ejr. 238 Commutating poles, auxiliary, of 750 kw., 250 volt, 1500 R.P.M., C. C. generator 443 Commutation: Chief consideration in C. C. designs 334 Compensating windings for neutralizing reactance voltage 332 Effect on a and p for C. C. machinery 9 Interpoles for neutralizing reactance voltages 328, 332 Commutator : Brown Boveri's C. C. turbo-generators 426 Brushes, see Brushes and Brush Gear. Construction for high speeds A22-^l^ 750 kw., 250 volt, 1500 R.P.M., C. C. generator 443, 444 Grooved 497 Homopolar generators, Commutator unnecessary 455 Length of, in high speed machines 415 Losses, see Losses. Peripheral Sj)eed, see Peripheral Speed of Commutator. INDEX. 607 Commutator. — Continued. Segments methods of interlocking 423 Sparking, suppression of 400, fig. 402 Speed, Effect on dimensions 477 Stress calculations for 1000 kw., 1000 R.P.M., C. C. generator .... 466-467 Ventilation 424, fig. 423, 424 Comparative study of C. C. designs 378 el seq Compensating Winding, see Windings, C. C. Conductors: 650 kva. alternators, number, determination of Ill 3000 kva. alternators. Number per slot 159 Size, Determination of 166 Connections: Methods of attaching to carbon brushes 487-491 and figs. Construction of High Speed Alternators, see A. C. machinery. Construction of High Speed C. C. Generators, see C. C. machineiy. Contact resistance brush: Investigation of 471-477, 480 Morgan Crucible Company 485, fig. 484 Continuous current generators 319 et seq Armature heating coefficients. Methods of estimating 36-38 Barrel wound armatures. Thermal calculations 28 Brown, Boveri & Co., Standardization of turbo-dynamos up to 1250 kva. rated output 283 Brushes and brush gear for 468 et seq Chief considerations 88 Commutation and Commutators, see those titles. Comparative study of designs 378 et seq Construction of, high speed generators 412 et seq Allgemeine Elektricit&ts Gesellschaft machines 450-454 Armature core plates. Low loss sheets for • • . 45-47 British Westinghouse Company's machines 445-450 Brown, Boveri & Co.'s machines 426-437 Homopolar Generator, see that subheading. Rateau Turbine Company of Chicago 453-455 Siemens Bros, machines 438-442 and figs. 750 kw., 250 volt, 150 R.P.M. machine 442-445 1000 kw., 1000 R.P.M., 6-pole for different voltages, Study and outline sketches 412-417 Design Methods: Comparison between routine and design: Chart methods 382 et seq Routine calculations 364 et seq Three sets of designs for different speeds; Calculations, 364; Specifi- cations 367-371 fig. 383 Preliminary design charts for 346-363 Study of 45 designs . 360-363, 384, figs. 383, 384-393 Troublesome ratings and proposals for design ' 394 et seq General considerations relating to influence of rated output, voltage and speed on design 319 et seq High speeds, Limited experience 332 508 INDEX. Continuous current generators. — Continued. Homopolar or cyclic generators 455-460 Axial type 455, fig. 456 Noeggerath 300 kw., 500 volt turbine-driven machine, 454-458; Efficiency curve 459 Slip ring losses 481 Radial type 455, fig. 456 Westinghouse Company 460 Interpoles, see that title. Leading dimensions of large high speed machines, Determination of . . 334 ei seq Preliminaiy design charts 346-363 Output coefficient 14h-17, 343 Armature diameter, Relation between 15 Rated output, Relation between 14 Voltage, Relation between 344 Preliminary designs for various rated outputs and speeds 364 €t seg 250 kw., 250 volt machine for different speeds 365 Efficiencies at different loads 381 Specifications and drawings 367-371 Speed, most economical for 378 Technical data at most economical speed, 1500 R.P.M 379 Total Works Cost and other data 373-377 500 kw., 500 volt machines for different speeds: Commutator dimensions 477 Efficiencies at different loads 381 Sp)ecifications and drawings 367-371 Speed, most economical, 1000 R.P.M. — Technical data 380 Total Works Cost, and other data facing 377 1000 kw., 1000 volt machines for different speeds: Efficiencies at different loads 381 Specifications 367-373 Speed, 750 R.P.M. most economical: Technical data • 380-398 11,000 R.P.M. machine, Study of 395-402 Study of 1000 R.P.M. machine 395-402 Alternative designs, 398 — Leading data of 397 Interpoles, Rearrangement of 399-401 Total Works Cost and other data facing 377 Principles of design for high and low speeds 322 et seq 500 kw., 250 volt machines for various speeds designed on three different principles 323-324 fig. 325 Reactance voltage 0, Estimation of 334 el aeq Curve showing value of x in formula for 335 Design chart for determining facing 347 Rotary converter scheme. Calculations for 403-411 Rotors, Choice of material for 58 Speeds: Coupling 2 dynamos on one turbine shaft 381 Efficiencies 382 High versus Low , 1, 2 Low, most satisfactory for designing 4, 324 INDEX. 509 Continuous current generators. — Continued. Stresses in a rotating armature 460 Calculations for 1000 kw., 1000 volt, 1000 R.P.M., C. C. machine . . 461-467 Temperature test of field spools of 4-poIe machines 42 Total Works Cost: Methods of estimating 25 Predetermination of 366, 372 Speed relation between 320-324 Troublesome ratings and proposals for design 394 el aeq 1000 kw., 1000 volt, 1000 R.P.M. generator: Specification and outline drawings 367-373 Further study 395-402 Alternative designs, 398 — Leading data 397 Interpoles, Rearrangement of 399-401 Stress calculations 461-467 Voltage coefficient 14 Weight coefficient 24 D>^ and relation between fig. 26. 500 kw., 250 volt, 125 R.P.M. machines, Design of 350-359 Alternative trial designs 351 For different speeds 355-359 and cwrvea Desi^ chart . facing 348 Leading data of 12- and 16-pole design 354 6-poIe, 1000 R.P.M. design: Output coefficient calculations 345 Pole pitch (t), Value of, note 339 Reactance voltage calculations 337 et eeq C. C. versus A. C. Machinery: Output coefficients 15 Weight factor 24 Copper for field spools. Weight dependent on section of magnet cores . . 328-332 Copper Losses, see Losses. Core Loss, see Losses. Core loss test on 500 kva. alternator 146-152 Cost Coefficients, see Design Coefficients. Costs, see Weights and Costs. Criteria for heating temperature rise 27 et seq Current: Collection from brush 487, 489 Density and brush contact resistance, Relation between . . . 472, 485, fig. 484 Curtis Turbine, see Turbines, Steam. D. De Laval Turbines, see Turbines, Steam. Definite Pole Field Sitructures, see Rotating Field Systems. Demagnetizing Ampere Turns, see Armature Ampere Turns. Design Charts, see Preliminary Design Charts. Design coefficients for dynamo electric machinery 6 et seq Cost 6, 25-26, 373 Output 6-18 A. C. machinery 10-14 610 INDEX. Design coefficients for dynamo electric machinery. — Continued, Basis for design 103-107 400 kva. machines 137-139 650 kva. machines 108 3000 kva. machines 157, 170 6000 kva. machines 206, fig. 205 Values for 30 alternators of various speeds and ratings 100, 101 C. C. machinery 14-17, 343 C. C. V, A. C. machinery 15 Inter-relation of 6-10 Rated speed and, Relation between, for 3000 kva. alternators for different speeds and numbers of poles 170, 171, 188 Relation between ^ and ^ 18 Specific utilization coefficients and ^, Relation between 206, fig. 205 Steinmetz (^) 6, 17 Use of (e) 16 [See aUo Specific Utilization Coefficients ] Weight 6, 18-25 A. C. machines 18-24 Comparison between 1500, 3000 and 6000 kva. alternators .... 213, 216 3000 kva. alternators for various speeds, 25 cycle machines, 170, 179, 180 — 50 cycle machines 193, fig.l91 6000 kva. alternators 204, 209 C. C. machines 24 Dettmar. Temperature tests of insulation on field conductors 43 Dick Kerr & Co. : Rotor of turbo-alternator, 269, fi^. 268, 269: — Method of attaching pole cores and pole shoes 271, fig. 270 Distorting Ampere Turns, see Armature Ampere Turns. Distributed Compensated Windings, see Windings, C. C. Distribution of losses in 3000 kva. alternators for various speeds, 25 cycle machines, 172-175: — 50 cycle machines 190 Double coil 230 E. Eddy Current Losses, see Losses. Effective Material, see Material. Efficiency of Continuous current generators at different loads 381 Curve of 300 kw. Noeggerath homopolar generator 453 400 kva. alternators 136, 139, 140 3000 kva. alternators '. 167 End bell of Washington rotor 257 End connections, Method of retaining 421 End Windings, see Windings, End. "Endruweil" brush 483 Epstein method of testing iron 52 Esson. Temperature rise of field coils, note . 41 Excitation regulation 66 Brown Boveri & Co. C. C. turbo-dynamos 427 4-pole, 1000 kw., 550 volt, 1250 R.P.M. machine 433 INDEX.. 611 Excitation regulation. — Covdinued. Data for 1000 kw., 6-phase turbo-alternator for use with lotaiy converter . . 407-411 3000 kva. alternators 162, 163 6000 kva. alternators 82-87, tabU and figs. Expansion pigtail 489 F. Factor of Safety, see Safety Factor. Field coil: Retaining pieces 274 Temperature rise of, 41: — Test results on 4>pole C. C. machine .... 42 Ventilation of 43 Constructions for water wheel generators 272 Copper space for, in high speed alternator design 114 650 kva. alternator, Calculations for 129 3000 kva. alternators. Calculations for 161 Excitation calculations in 650 kva. alternator 122 Magnet stampings 275 Spool: Calculations for 3000 kva. alternators 163 C. C. machines. Weight of copper and section of cores, Relation between, 328-^32 System, Brown Boveri's, C. C. turbo-dynamo 426 Winding calculations for 3000 kva. alternators 164 Figure of Loss, see Losses. Flexible Connectors, eee Connectors. Floor space. Brown Boveri's standardized line of C. C. turbo-generators, 437, fi>g, 436 Flux: Densities in iron and steel 79,80, 113 Determination of, for 650 kva. alternator 110 3000 kva. alternators 158, 159 Poles, Number of, Depth of air gap and armature strength, Relation between, for 3000 kva. alternators for various speeds 17^178 and figs. Forced Ventilation, aee Ventilation. Frequency: Influence of, From outline designs for 3000 kva. alternators for various speeds, 156 et eeq Speed, Niunber of poles and, Relation between 7, 205 Friction Coefficient. Metal and carbon brushes 471 G. Galvanic Metal Paper Company of Berlin, " Endruweit " or " Galvano " brush . 483 "Galvano" brush 483 Gas engine. Speed and output. Relation between, for 2, /i{^. 3 319 General considerations l^et eeq General Electric Company of America: Armature windings of 3000 kva., 4-pole alternator, Method of retaining, 242, fi^, 241 512 INDEX. General Electric Company of America. — Contimned. Definite pole rotor construction 266, fig. 265 Method of retaining field coils 267, figs. 264, 266 Stress calculations * 309 Homopolar generators 457-459 300 kw., 500 volt turbine driven C. C. machine 458 Efficiency curve 459 Slip ring losses 481 Pole cores and shoes, Methods of attaching, to rotating fields 270 Rotating field structures 261, fig, 262 Stator frame, Section of turbo-alternator 221 General procedure in alternator design, see A. C. Machineiy. Goldschmidt, Temperature rise of field coils, note 41 Graphite brushes 469, 412, 415 Grooved commutators '. 494 H. Heating: Armature core plates, Effect of grade on • 45-49, 51 Calculation of 650 kva. alternator 120 3000 kva. alternators 167, 168 Criteria for 27,et seq Effect of, on a and ^ . 9 Peripheral speeds of rotor. Relation between, for a number of alternator designs 32-34 Heyland compounded turbo-alternator: Description 301-303 Rotating armature and rotating field design, Comparison 304 High speed Alternators, Construction of, see A. C. Machineiy. C. C. Generators, Construction of, see C. C. Machinery. High V. low speed alternators: Leading data of 30 alternators of various speeds and ratings 99-102 Specification and comparison between a 94 R.P.M. and 1000 R.P.M. gen- erator 95-99, fig. 94 Temperature rise data 89 Pressure regulation data 92 Weights and costs of active material 98-99 Homopolar Generators, see C. C. Machineiy. Hub: 650 kva., 4-pole alternator, stress calculations 308 1500 kva., 6-pole alternator, stress calculations 312 Hydraulic turbine speeds 2, 319 Hysteresis Loss, see Losses. I. Induced Ventilation, see Ventilation. Inductance of armature windings, Estimation of 70 Induction motors, Heating coefficient for 36 Inductor type generator of Oerlikon Company 276 INDEX. 513 Influence of speed and number of poles on designs for 400 kva. alternators, 131 et aeq Inherent Regulation, see Pressure Regulation. Insulation, E£fect of temperature on 43 Internal phase angle <f>* 66 Components ^' — ^ + a + .5 68 4>, determination of 69 a, determination of 69 fi, determination of 73 Interpoles for neutralizing reactance voltage 344, 417, 418 Design of machines with 394 Reactance voltage not necessarily very low in such machines, note . . . 352 Disadvantages of 328 Function and use of * . . . 328 Iron distribution of, in high and low speed alternators 99 K. Kolben & Co. bipolar alternators 146 Krupp Works, Essen, Strength of materials 59 Lahmeyer Company: Arrangements for securing end windings 243 Rotating field construction 251 Stator frames for turbo-alternators 222, figs. 222, 223 Laminated brushes 482 Laminations, see Armature Core Plates. Lap coil 231, fig,2dO Le Carbone Brushes, see Brushes, Carbon. Leakage Coefficient. Estimation of leakage and useful flux 76 In 650 kva. alternator 114 Leakage factor; larger in interpole designs ; 328 Leakage Flux, see Leakage Coefficient. Lever type spring pressure brush holder 491 and fig. Linear Speed, see Speeds, Peripheral. " Lohys " figure of loss 56 London, W. J., on brushes 470 London Underground Electric Railway Company: Westinghouse 5500 kw. alternator: Armatures 238, fig, 236, 237 Rotors 248,257 Armature: Estimation for 650 kva. alternator 119, 120 Temperature rise and 27 Commutator: Contact resistance 475 Bronskohl brushes 487 and curve Moiganite brushes 485 and curve 514 INDEX. Losses. — CanHnued. Friction 476 Bronskohl brushes 487 and curve Moiganite brushes 485 and curve Total Losses: Bronskohl brushes 487 and curve Morganite brushes 485 and curve Copper: 400 kva. alternators 136, 141, fig. 140 650 kva. alternators 120, 130 3000 kva. alternators 167 Core: Copper percentage of, to iron '. 117 Reduction of Rotating annature, Advantages of 154 Special low loss sheet steel for 45 et «eg Use in 400 kva. alternators 140 Total internal loss, Percentage of, constituted by 45, 47 [See also Figure of Loss]. Diminution, advantages of smooth drum rotating field 275 Eddy Current: Dependent upon specific resistance of iron 54-56 Electrical and magnetic, in 400 kva. alternators 135, 139, 140 Field P 22: Interpole designs 328 500 kva. alternator 147-152 Figure of Loss: Armature core plates 53-57 Definition of 50 Hysteresis in low loss steels 56 Iron, Estimation of, for A. C. generators 119 400 kva. alternators 135, 140 3000 kva. alternators 167 Slip ring, in homopolar generators 456 Speed, Relation between, and 172, 173, 189 and 190 Teeth, Estimation of, in 650 kva. alternators 120 Total internal, Percentage constituted by core loss 45, 47 Total, and heating in 650 kva. alternator 120, 130 3000 kva. alternators for various speeds: 25 cycles, 141 : — Distribution of 172-175 50 cycles 189 Low Loss Sheet Steel, see under Materials for Construction. Low Speed v. High Speed Machines, eee High Speed v. Low Speed Bfachines. M. Magnet: Cores 76 Dimensions, Determination of, for 3000 kva. alternators .... 159, 160, 169 Interpoles, Effect on shape 328-332 Frame of 750 kw., 250 volt, 1500 R.P.M., C. C. generator 443 Poles: Circular versus rectangular 110 INDEX. 615 Magnet. — Continued. 650 kva., 4>pole alternator 113 Stress calculations 305 Yoke: C. C. machines self supporting 24 Dimensions, Determination of, for 3000 kva. alternators 160 Water wheel generators 272 Magnetic: Circuit, Calculation of, in 650 kva. alternator design 121 Flux densities ^ 79, 80, 113 Per pole in alternators 91 Leakage: Ampere Turns for Increased/ see under Armature Ampere Turns. Leakage coefficients smaller for high speed machines 92 Material, Permeability of 57 Manchester Electricity Works, Description of 750 kw., 500 volt, 1600 R.P.M. C. C. turbo-generator 439-442 Martin, Parsons & Stoney, on brushes 470 Material: Effective 18 C. C. machines 24 Weights for several alternators 21, table 20 Weights and costs of, in low and high speed alternators 99 Non-effective relation between air-gap diameters and 21 Materials for construction of high speed electrical machinery 5, 45 eteeq Armature core plates: Cost 57 Customary dimensions 53 Figure of loss 53-57 Special low loss sheet steel 4betseq Cost 57 Figure of loss 55, 56 Mechanical strength 61 Stalloy: Figure of loss 55-56 Mechanical strength 61 Use in 400 kva. alternator 140 Testing of 52 Brown, Boveri <fe Co.'s C. C. turbo-generator 426 Brushes and brush gear 468 et seq Ceylon graphite for Moiganite brushes 485 End bells for retaining armature windings 421 End cover of armature and field windings 61 Magnet poles for 650 kva. alternator 113 Magnet yoke: Water wheel generators 272 3000 kva. alternators for different speeds and numbers of poles 160 Magnetic, Permeability of 57 Rotating fields 2A7 et seq Rotors 58 Stalloy, and special quality steels for 61, 62 516 INDEX. Materials for construction of high speed electrical machinery. — ConJtinv/9d, 650 kva. 4>pole alternator 113, 114 Alternative construction 305 Steel binding wires for retaining end connections 421 Stresses and elastic limits 58, 305 Data for 63, 64 and 306 Methods of estimating armature temperature rise 27 etseq Metropolitan railway of London, rotor of 33 cycle, 3500 kw. alternator for . 256, 257 Miles Walker compensated rotating field structure 258-260 Molnar on manufacture of brushes 478, 479 Morgan Crucible Company brushes 483-485 Method of attaching "pigtail" 489 Brush holders 494-497 Myer, H. S., on treatment of field coils 287 N. National Carbon Company, compound brushes 482 Method of attaching "pigtail" 489 National Physical Laboratory of Great Britain, temperature tesls on insulating material 43 New and Levine temperature rise of field coils, note 41 New York Edison Company, Rotors of 9000 kva. generator for. . . . 261, fig. 262 No Load Saturation Curve 9ee Saturation Curve. Noeggerath: Brush contact resistance 481 Homopolar generator 458, fig, 457 Efficiency curve 459 Slip ring losses I 481 Non-effective Material, see Material. O. Oeriikon Company: Temperature rise of field coils, note 41 Turbo-alternators, Development of 276-283 Inductor type 276 Rotating armature typQ 276 Early type 251, fig, 253 Rotating field construction 249, 250, 276 Early types and development of 251-256 .an^ figs. 1200 kva., 3-phase, 1500 R.P.M., 4-pole, 50 cycle, 1155-2000 volt — Data and outline drawings 276 Ventilation scheme for 224-226 Armature and stator frames 226, figs. 226-228 Winding of Armature of 400 kw. machine 236, fig. 235 Method of securing end windings 242, figs. 235, 240 250 kw., 3-phase, 3000 R.P.M., 2-pole, 50 cycle alternator, data and out- line drawings 277 1000 kva., 1500 R.P.M., 4-pole, 50 cycle, 5200 volt single phase: Characteristic curves 283 Data and outline drawings 278-283 INDEX. 617 Oerlikon Company. — Covdinued, 200 kw., 3000 R.P.M., 220-250 volt., C. C. machine: Annature and field system of figa. 419, 420 Commutator, Description of '. 423 Open Type Stator Frame, ue Stator Frames. Output: Coefficients, see Design Coefficients. Per pole for 30 alternators of various speeds and ratings 100, 101 Rated output and output coefficient, Relation between 10, 14 Speed, Influence of 12 Speed, Relation between 2-4 General conclusions 217 Influence of rated output and speed on design of A. C. generators . . 88 «< «eg Influence of rated output and speed on design of C. C. generators . . 319 et seq P. Parsons, Messrs. : Annature of 18,000 R.P.M. turbo-dynamo, Early type 419 Commutator 422 C. C. brush gear, Early type 470 Rotating field structures, Method of attaching pole cores and pole shoes, 271, fig, 270 Turbine, see Turbines, Steam. Parsons & Stoney, Compensating winding 470 Parsons, Stoney & Martin, on brushes 470 Peripheral speed 321 Commutator, Considerations 326, 327 Brush contact resistance and. Relation between 473 (For) Materials of different strengths 60, 61 Temperature rise and, Relation between 29 Tests showing effect of temperature rise of field coils 42 (For) 30 alternators of various speeds and ratings 100, 101 Permeability of magnetic materials 57 Pigtail, Method of attaching to carbon brushes 487-491 and figs. Pilot Brushes, see Brushes, Compound. Piston Engines: Speed and output, Relation between 2, fig. 3, 319 Steam turbines and, Comparison for driving C. C. machinery .... 416, 417 Pneumatic brush holders 495-497 Pohl, on homopolar generators 459 Pole: Cores: Diameter, note 330 Methods of attaching 269-271 Stress calculations 307 Stress calculations: 650 kva., 4'pole alternator 305 1500 kva., 6-pole alternator 310 Pitch (r) : Armature length, Ratio to: Value in 6-pole, 1000 R.P.M., C. C. designs, note 339 Values for 30 alternators of various speeds and ratings 100, 101 618 INDEX. Pole. — CanHnued. Shoes: Methods of attaching 260-271 Stress calculations 307 Poles, Number of: Flux, Depth of air gap and armature strength, Relation between, for'3000 kva. alternators for various speeds 175-178 and fig8. Influence on outline designs for 3000 kva. alternators, 156 et seq — for 400 kva. altematorf 131 Reactance voltage and, Relation between, in C. C. machines 336 Speed and Frequency, Relation between 7 (For) 30 alternators of various speeds and ratings 100,101 Polyphase Alternators, see A. C. Machinery. Preliminary design charts for C. C. machines 346-363 Pressure, Brush and contact resistance, Relation between 472 Moiganite brushes 485, fig. 484 Pressure regulation: Calculation for: 400 kva. alternators 130, 141-143 650 kva. alternator 123-125 ££fect of, on a and fi for alternators 9-15 Inherent regulation 65, 90 Power factor « 1 65 Calculations 78 for 650 kva. alternator 125,130 for high and low speed alternator (94 and 1000 R.P.M.) 97 Power factor — 0.8, calculations 65-77 Calculations for high and low speed alternator 97 for 650 kva. alternator 125, 130 for 3000 kva. alternator 71-77 Speed and, Relation between 90 Saturation of magnetic circuit, Relation between 79, 162 Short circuit characteristic. Relation between 79, 80 Strong and weak armatures 80 Tests on 500 kva. bi-polar alternator 152 Vector diagrams 68, 69 [See also Excitation Regulation and A. C. Machinery.] Progressive wave windings 234, fi^. 233 Punga,i2e/. to ''Sudden Short Circuiting of Alternators" 242 R. Radial l^pe Homopolar Generator, see Continuous Current Machinery. Rateau Turbine Company of C^iicago, 100 kw., 3000 R.P.M., 125 volt, C. C. turbo-dynamo 454, fig. 453 Reactance Voltage: Ampere turns required for 66, 74-76, 91 Determination of 69 Estimation of, in C. C. machines 334 et seq Calculations for 6-pole, 1000 R.P.M. design 337 et aeq Design chart for determining facing 347 Value of coefficient 335 Neutralizing of. Compensating windings and interpoles for 332, 344 INDEX. 519 Reaction type spring pressure brush holder 491, 450 and fig. Reactions, Annature, Calculations for 650 kva. alternator 123, 124 Regulation Calculations, see Pressure Regulations and Excitation Regulation. Retrogressiye wave windings 234, 235, fig. 233 Rhenish Westphalian Electricity Works at Essen, Steam turi>ine set, 436, fig. 433, 434 Richardson Westgarth & Brown Boveri 4-pole, 1000 kw., 650 volt, 1250 R.P.M. C. C. turbo-generator 431-435 Brush gear for 486 Riedler, Dr., on strength of materials 60 Rotaiy converters as substitutes for Speed Reduction Gearing 403-411 Rotating armature system 219 C. C. machines — choice of materials 58 Hyland's self-compounding turbo-alternator 301 Comparison with ordinaiy rotating field alternator 304 Oerlikon 2520 R.P.M. alternator 276 Specific temperature, rise of field coils 41, 43, 44 Stresses in 460 Calculations for 1000 kw., 1000 volt, 1000 R.P.M., C. C. generator . . 461-467 Rotating field system for high speed alternators 219, 246 Definite pole types 248, 256, 258, 265-269 Comparison with smooth drawn type 275 Construction of 650 kva., 4-pole alternator 113, 114 Stress calculations for alternative constructor 305 Construction of 1500 kva., 6-pole alternator • 284 Stress calculations 310 Methods of attaching pole shoes and covers 269-271 Stress calculations 307 Stress calculations 305-316 Heyland self-cOhipounding rotating armature alternator, Comparison with 304 Material for 58, 59 and 60 Methods of attaching pole shoes and covers 269-271 Stress calculations 307 Oeriikon alternators 276-283 Smooth drum type 248-265 Advantages and comparisons 275 Stress calculations 316 Stresses in 126, 305, et seq Water wheel generators 272 Rotors: Choice of material for 58 Stalloy and special quality steel 61, 62 Core Ducts, «€« Ventilating Ducts. Peripheral speed of, and specific temperature rise 29 Ventilation of, in 2-pole designs 141, 146 Rushmore, D. B., field construction for water wheel generators, 272-273, figs. 271-273 S. Safety factor 58, 59, 60 Sankey, Messrs. Joseph & Sons, q)ecial low loss sheet steels 56, 61, 62 Saturation, Higher, in rotating armature designs 153 620 INDEX. Saturation curve: No load (for), . Ampere sums for reactance voltage, Use of, in calculating . . . . 74, /S^. 75 Effect on regulation 79-162 500 kva. alternator 147, fig, 148 650 kva. alternator 123 1000 kva. Oerlikon altematois 282, fig. 283 Saturation curves, for showing permeability of magnetic materials . 57, 58, fig, 59 Sayers, W. B., on metal and carbon brushes 470 Scott & Mountain: 500 kw., 3-phase, 4-pole, 1500 R.P.M., 50 cycle, 550 volt, turbo-alternator, description 295-301 Specification for 298 Stress calculations 316 Short circuit: Characteristic. Oerlikon 1000 kva. alternator 282, fig, 283 Regulation and relation between 79, 80 Current high speeds and pressure regulation 92 Loss test on 500 kva. alternator 146, 150 Siemens Bros. Dynamos Works Ltd. : A. C. machines, ventilation of turbo-alternator, Enclosed frame for . 226, fig, 229 C. C. machines. 750 kw., 1600 R.P.M., 500 volt, turbo-generator 439-442 Commutator ventilation 424, fig, 423 and 424 500 kw., 1500 R.P.M., 250 volt, turbo-generator 438 Siemens Schuckert Werke rotating field structure . 265, fig. 264 Single coil 230 Single Phase Windings, see Windings. Slip ring losses in Homopolar generators 456 Slots: Insulation thickness for, A. C. generators 117 Number per pole per phase 92 In 650 kva. alternators 111-113 In 3000 kva. alternators for various numbers of poles 159 Slots and teeth: Calculations for 650 kva. alternator 116, 117, fig. 118, 128 Stress calculations for 1000 kva. C. C. generator 462 Sparking at Commutator, see Commutator. Specific Electric and Magnetic Loading of Armature (a & /9), see Specific Utili- zation Coeflicients. Specific Temperature Rise, see Temperature Rise. Specific utilization coeflicients a and fi 6, 8 Components of ^ 68 Determination of a 69 Determination of /? 73 Determination of, in alternator design 106, 107 Dimensions dependent upon 9 Relation to output coefficient 8, 17, 139, and 171 Speed and, Relation between, in: 400 kva, alternators 137-139 3000 kva. alternators 171, 173, fig. 172, 188, 189 INDEX. 621 Specific utilisation coefficients a and fi. — Continued. Values higher in C. C. than in A. C. machines 15 Values in 6000 kva. designs . . 204, 206, fig. 205 Speeds: Allgemeine Elektricitfits Gesellschaft C. C. turbo-generators: With metal brushes 452 With carbon brushes 454 A. C. machineiy, Influence of rated speed and design 88 et seq 400 kva. machines 131 3000 kva. machines 156 et aeq 25 cycle designs 170 50 cycle designs 188 Angular 321 Commutator dimensions, and, Relation between ■ 477 C. C. machinery, Influence of rated speed on design 319 et seq Frequency and, Relation between 205 Frequency, number of poles, and relation between 7 High: C. C. machineiy 1, 2 Core loss, Percentage of total internal loss for 47 Development of 1, 218 General conclusions 217 Low versus, for C. C. machinery 1, 2 Study of, Alternators 197 et seq Losses and, Relation between 172, 173, 189, 190 Low: C. C. machinery 1, 2 Core loss, Percentage of total internal loss for 45 Output coefficient of polyphase alternators 10,11 Output and, Relation between 2-4 General conclusions 217 Output coefficients and, Relation between 12, 88, 170 Pressure regulation and, Relation between 90 Reduction of, Rotaiy converter scheme 403-411 Regulation of 4-pole, 1000 kw., 550 volt, 1250 R.P.M., Brown^Boveri's C. C. turbo-generator 431 Steam turbine. Uneconomical for driving C. C. machinery 415-417 Rotary converter scheme for 403-411 Total works cost, and. Relation between 4, 320-324 See also Peripheral Speeds. Spiral Coil, see Coil. Spring arm type brush holder 491 and fig. Spring pressure type brush holders 487-495 Stalloy 55, 56 Mechanical strength and physical tests 61 Standardization rules of the A. I. E. E., Efficiency of A. C. generator .... 149 Stationaiy Armatures, Specific temperature rise of field coils 41, 43 Stator, Description of 4-pole, 1000 kw., 550 volt., 1250 R.P.M., C. C. turbo- alternator 434 Stator frames for high speed alternators 219 y et seq Forced or induced type 222-227, figs. 222-230 622 INDEX. Stator frames for high speed altematoiB. — Continued. Open type 219-221 Steam Engines, see Piston Engines. Steam Turbines, see Turbines, Steam. Steinmetz Coefficient, see Design Coefficients, Output. Stodola, on strength of materials 59 Stoney, Martin & Parsons on carbon brushes 470 Stoney & Parsons, Compensation windings 470 Stresses: Rotating armature systems 58, 460-467 Calculations for 1000 kw., 1000 volt, 1000 R,P.M., C. C. generator . .461-467 Rotating field systems 58, 126, 305, et m^ Definite pole structures: 650 kva., 4-pole alternator 305^10 1500 kva., 6-pole alternator 310 Comparison between 4- and 6-pole machines 310 Smooth drum type, Calculations for 500 kw., 4-pole alternator 316 Water wheel generators 272 Various materials 58, 63, 64, 306 Strong armature. Definition 80 Stimipf, Prof., on strength of materials 60 Swinboume & Crumption, Rotating field magnet 248 T. 