Armature

ELECTRICAL MACHINE DESIGN

Design 1 : DC Generator Armature Design

Submitted by

PINEDA,JON ADRIEL S.BSEE V-3Submitted toENGR. LIBRADO S. GESALTA

InstructorJULY 4, 2014Design Sheet for a DC Generator Armature

ITEM NO.SPECIFICATION :

185 KW, 440V, 500rpm, DC Generator SYMBOLPRELIMINARY OR ASSUMED VALUESFINAL VALUES

=====PART 1 : ARMATURE CORE & WINDING =================================================

1Number of poles / frequencyP /f14 poles / 60 Hz

2Ratio of pole arc to pole pitchR0.640.64

3Specific loadingQ13001300

4Apparent air-gap densityBg6750067500lines/in.2

5Line currentI4204.545 A4204.545 A

6Type of windingLap Winding

7Armature current per circuitIc702.86 A702.86 A

8Output factorlaD239925.21427331.264

9Armature diameterD58.2559 in.

10Peripheral velocityV7624.95 fpm7624.95 fpm

11Total number of phase conductorsZ971.56972

12Number of slotsS43461

13Number of conductors per slot4

14Axial length of armature corela16.91 in.22.41 in.

15Flux per pole8.4 106 maxwells15.09 106 maxwells

16Pole pitchT14.53 in.8.13 in.

17Pole arc 10.32 in.5.772 in.

18Area covered by pole face174.51 in.2 232.44 in.2

19Dimensions of armature conductors0.0955 in. 0.42 in.

20Slot pitch0.3746 in.4.79 in.

21Slot widthS0.5 in.

22Slot depthD1.14 in.

23Tooth width : at top at root average0.5742 in. 0.1517 in.0.3630 in.

24Number of radial ventilating ductsN5

25Width of radial ducts1 in.

26Net length of armature coreln10.96

27Net tooth section under pole, at the center29.66 in.2

28Apparent density at teeth under pole at centerBt283 103 maxwells123 103 maxwells

29Length per turn of armature coil2512.61 in.

30Resistance of one turn, ohms at 60C0.0246

31Resistance of armature0.15

32IR drops in the armature5.15 V

33I2R loss in armature winding46814.74 watts

34Estimated full-load flux per pole8.5 106 maxwells

35Flux density in armature core below teeth73000 lines/ in.2

36Internal diameter of core stampings80.1 in.

37Weight of iron in core(without teeth)4372.43 lbs.

38Weight of iron in teeth61.02 lbs.

39Total weight of armature stampings4433.45 lbs.

=====PART 2 : Commutator & Brushes=================================================

40Diameter of CommutatorDc50.5 in.

41Average volts per turn of armature winding21.31 V

42Number of turns between bars1

43Total number of commutator bars870

44Bar pitch0.3734 in.

45Width of copper bar0.3434 in.

46Radial depth of bar16.57 in.

47Current density at brush contact surface b40 amps/in.239.84 amps/in.2

48Contact area per brush set34.86 in.235 in.2

49Brush arc1

50Axial brush length per set27.5 in.

51Number of brushes per set22

52Axial length of commutatorLc?36.38 in.

53Brush-contact drop2 V2.3 V

54Brush-contact loss9621.82 watts

55Brush-contact friction3227.82 watts

56Total brush loss12849.64 watts

57Drawing to scale giving leading dimensions of armature and commutator

Solutions:PART 1:

Poles / Frequency

@ 60Hz

P = _60 Hz 120_

P = 14 poles @ 60 Hz frequency

500rpm

Line Current

I = _1850000 w_

I = 4204.5 A

440V

Armature current per circuit

Ic = _4204.5 1.004

Ic = 702.86 A

6

Armature Diameter______________________

D = 3 _875000_ ____6.06 108_____

D = 58.25 in.

___360______65500 0.71 1250_

0.202

Gross Armature Length

Ia = 0.1828 51.75

Ia = 0.202 in.

Output Factor

IaD2 = _1850000_ ____6.06 108_____

IaD2 =39925.214

500 67500 0.71 1250 Peripheral Velocity

v = _58.25 500

v = 7624.95 fpm

12

Number of phase conductors

Z = _51.75 1250 _

Z = 971.56

209.17 Flux per Pole

= _440 60 40 108_

= 15.09 106 maxwells

20 360 971.56 Slot Pitch

= _51.75 _

= 0.3746 in.

434

Slots per Pole

Slots per pole = _434_

Slots per pole= 21.7

20 Specific loading

q = _244 209.17_

q = 313.93 51.75 Pole Pitch

T = _51.75 _

T = 8.13 in.

20 Pole Arc

= 8.13 0.71

= 5.772 in.

Pole Area

Ia = 5.772 16.91

Ia = 97.61 in.2 Air-gap density (final)

Bg = _8.4 106_

Bg = 86056.76 lines/in.2

97.61 Slot width

s = 0.5 (assumed)

s = 0.5 in. Slot depth

d = 0.191 + (3 0.035) + (2 0.42)

d = 1.14 in.

Tooth width at the top

Ttop = 0.6697 0.0955

Ttop = 0.5742 in. Tooth width at the root

Troot = (283.5 435) 0.5

Troot = 0.1517 in.

Tooth width average

Taverage = _0.5742 + 0.1517_

Taverage = 0.363 in.

2 Ventilating ducts

*Use 5 ducts with 1in. width

* 5 ducts 1 in. wide Net length of the armature core

In = 0.92 [16.91 - (5 1)]

In = 10.96 in.

Net tooth cross section under pole

Tooth Section = 10.96 0.363 _105_ 0.71

Tooth Section = 29.66 in.2

10

Apparent Flux Density at teeth

Bt = _8.4 106_

Bt = 283 103 maxwells

29.66 Length per turn of armature coil

lc = 56.06 in.;la = 22.41 in.

L/T = 56.06 2(22.41)

L/T = 2512.61 in.

Resistance at 60C

R@60C = _________2512.61__________

R@60C = 0.0246

2(0.0955 0.42) (4 ) 106Resistance of the armature

Ra = 0.0246 _(244 2)_

Ra = 0.15

20

IR drop in the armature

IR = 209.17 0.0246

IR = 5.15 V I2R loss in the armature

I2R = 209.172 0.246

I2R = 46814.74 watts Full-load flux per pole

FL = _8.4 106 445.23_

FL = 8.5 106 maxwells

440 Internal diameter of core stampings

Dinternal = 93 (2 5.31) (2 1.14)

Dinternal = 80.1 in. Weight of iron in core (without teeth)

Wcore = _0.28 10.96 _ [(93 2.28)2 (80.1)2]

Wcore = 4372.43 lbs.

4

Weight of iron in teeth

Wteeth = 0.28 1.14 (0.0401) 10.96 435

Wteeth = 61.02 lbs.

Total weight of core stampings

Wtotal = 4372.43 + 61.02

Wtotal = 4433.45lbs.

PART 2 :

Diameter of Commutator

Dc = (93 2) + 4

Dc = 50.5 in.

Average volts per turn

Eaverage/turn = ___440___

Eaverage/turn = 21.31 V

413 20

Number of Commutator bars

*It is desirable to use 122 commutator segments to improve the commutation and to be more suitable and narrower. Bar pitch

Bar pitch = _14.5 _

Bar pitch = 0.3734 in.

122

Width of copper bar

WidthCu = 0.3734 - .03

WidthCu = 0.3434 in.

Radial depth of bar

h = _50.5 + 15_ _8765.062_

h = 16.57in.

15 45002

Current density at brush contact surface

Current density = 40 (34.86 35 )

Current density = 39.84 amps/ in.2 Contact area per brush set

b = _20 209.17_

b = 34.86 in.2

3 40 Axial brush length per set

*2.5 in. Axial length of commutator

Lc = 27.5 + 6.875 +0.625 + 1 + 0.375

Lc = 36.38 in.

Brush contact loss

LossBrush contact = 2.3 10 209.17

LossBrush contact = 9621.82w Brush contact friction

Wf = _0.25 2 6 10 50.5 360 _

Wf = 3227.82 w

20 33000

Total brush loss

LossTOTAL = 9621.82 + 3227.82

LossTOTAL = 12849.64 w

ARMATURE SLOTS/POLES

COMMUTATOR AND BRUSHES

DC GENERATOR AND ARMATURE

DATA TABLE

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