GENERATOR SELECTION CONTENTS - Diesel Generator

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LOAD (e) - 3 x 3 h.p. 3 phase motors. Steady State Transient SECTION 4595 January 1990 Page 3 From manufacturer’s data, the typical full load For the transient or starting condition, only one of running performance is: these motors will be started at any one time since they are started in sequence. In the absence of Efficiency = 0.78 p.u. actual starting performance data: Section 4522 Power Factor = 0.8 p.f. lag gives the maximum D.O.L. start kVA; thus: Then the steady state loading is: 3 x 0.746 x 7.1 3 x 3 x 0.746 = 8.6kW (Secction 4511) 0.78 = 15.9 start kVA per motor started and 8.6 = 10.8kVA 0.8 LOAD (f) - 1 x 80 h.p. motor. Steady State Transient From manufacturer’s data The transient or starting kVA derived from Section 4522 gives the maximum D.O.L. start kVA thus: Efficiency = 0.91 p.u. Actual Power Factor(given) 80 x 0.746 x 7.1 = 424kVA = 06. P.f.lag For auto transformer start at 80% tap (Section 4522) Then steady state loading is: 80 x 0.746 = 65.6kW (Section 4511) 0.91 Start kVA = 424 x (0.8)² and 65.6 = 109.3kVA 0.6 = 271 start kVA LOAD (g) - 1 x 80kW motor Steady State Transient Again from manufacturer’s data we obtain: The D.O.L. starting kVA required is calculated from the locked rotor current given; thus: (Section 4511) Efficiency = 0.91 p.u. Power Factor = 0.91 p.f. lag √3 x 415 x 750 = 539kVA for D.O.L start 1000 Hence the steady state loading is: For star/delta starting (Section 4522) the kVA on start is reduced to 0.33 of the D.O.L. value: 80 = 87.9kW (Section 4511) 0.91 Therefore start kVA = 539 = 180 start kVA 3 and 87.9 = 96.6kVA 0.91
LOAD SUMMATION SECTION 4595 January 1990 Page 4 We can not analyse these results and derive a final rating for a suitable a.c. generator. We shall make some further assumptions, and whenever such a calculation as this is attempted, it is essential that all assumptions made, are clearly detailed and passed on to the final customer. In this case assume:- (i) no two loads will be switched on simultaneously (ii) generally, the loads come on in the sequence given. (iii) for sizing purposes the effort of power factor (vector addition) during transient or motor starting loads is ignored since arithmetic addition of the loads will always give a larger kVA load figure than the vector addition. Summation of Single Phase Loads Load Steady State Transient kVA kW p.f Start kVA 1 2 3 4=3/2 5 6 (a) 2.5 2.4 0.95 - (b) 14.4 14.4 1.0 - (c) 12.0 9.6 0.8 71.0 (d) 9.1 3.6 0.4 - Total 38.0 30.0 0.79 This total single phase loading represents the worst possible case, as we have assumed that one particular phase always carried the highest unbalanced load current for each single phase load considered. In practice it is likely that the individual loads would be more evenly distributed between the three phases. However, for the purposes of sizing and in the absence of actual load connection data, this is a valid assumption. The steady state total single phase ratings can now be multiplied by 3 to obtain the equivalent 3 phase rating. Regarding the start kVA load of (c), this again is the worst case single phase surge kVA. The make up of load (c) is such that on start there is unbalanced surge kVA. Therefore the total 3 phase surge kVA on starting load (c) will be less than 3 times the worst case 71kVA. This product (213kVA) is in turn less than the highest 3 phase balanced start kVA which, from the table below, is 271kVA. Hence this single phase start kVA may in this case be ignored when considering the 3 phase summation table below. Summation of Three Phase Loads Load Steady State Transient kVA kW p.f. Start Total Load at Start kVA kVA 1 2 3 4=3/2 5 6 equiv. 3 phase for (a), (b), (c),(d) 114 90.0 0.79 (e) 10.8 8.6 0.8 15.9 114 + 15.9 = 129.4 (f) 109.3 65.6 0.6 271 114 + 10.8 + 271 = 395.8 (g) 96.6 87.9 0.91 180 114+10.8+109.3+180=414.1 TOTAL 330.7 252.1 0.76 ‘worst case’ is 114+10.8+96.6+271 = 492.4
Page 1 and 2: GENERATOR SELECTION SECTION 4 Janua
Page 3 and 4: SECTION DRAWING SINGLE BEARING WITH
Page 5 and 6: SECTION 4111 January, 1990 Page 2 C
Page 7 and 8: SECTION 4111 January 1990 Page 4 Op
Page 9 and 10: SECTION 4111 January, 1990 Page 6 P
Page 11 and 12: SECTION 4111 January, 1990 Page 8 T
Page 13 and 14: Figure 2 Curve (1) machine characte
Page 15 and 16: Introduction OPERATING PRINCIPLES S
Page 17 and 18: SECTION 4131 January, 1990 Page 3 S
Page 19 and 20: A.C. GENERATOR STANDARDS SECTION 43
Page 22 and 23: 1. Basic Data A C GENERATOR SELECTI
Page 24 and 25: POWER RATING SECTION 4311 January,
Page 26 and 27: TEMPERATURE AND TRANSIENT PERFORMAN
Page 28 and 29: CONTROL SYSTEM Stamford a.c. genera
Page 30 and 31: ALTITUDE SECTION 4411 January, 1990
Page 32 and 33: CLIMATE AND ENVIRONMENT SECTION 443
Page 34 and 35: SECTION 4501 January, 1990 Page 2 I
Page 36 and 37: SECTION 4511 January, 1990 Page 2 T
Page 38 and 39: CONSTANT OR STEAD STATE LOADS - SIN
Page 40 and 41: SECTION 4521 January 1990 Page 2 Be
Page 42 and 43: SECTION 4522 January 1990 Page 4 Wh
Page 44 and 45: Since I = kW genr. and I M = kW M _
Page 46 and 47: EXAMPLES OF SELECTION FOR VARIOUS L
Page 50 and 51: SECTION 4595 January 1990 Page 5 In
Page 52 and 53: POWER FACTOR CORRECTION SECTION 459
Page 54 and 55: Example Two - from an actual enquir
Page 56 and 57: Example Three To illustrate motor s
Page 58 and 59: FOREWORD ROTATING DIODE PROTECTION
Page 60 and 61: SECTION 4901 January 1990 Page 3
Page 62 and 63: 1. INTRODUCTION AND THEORY PARALLEL
Page 64 and 65: SECTION 4902 January 1990 Page 3 On
Page 66 and 67: SETTING THE DROOP CIRCUIT SECTION 4
Page 68 and 69: 4. WORKING PROCEDURE SECTION 4902 J
Page 70 and 71: 1. INTRODUCTION THREE PHASE SHORT C
Page 72 and 73: 4. SHORT CIRCUIT CURRENT DECREMENT
Page 74 and 75: CONTROL FOR GENERATORS IN PARALLEL
Page 76 and 77: SECTION 4951 January 1990 Page 3 Ma
Page 78 and 79: SECTION 4952 January 1990 Page 2 Se
Page 80 and 81: SECTION 4953 January 1990 Page 1 VO
Page 82 and 83: SECTION 4953 January 1990 Page 3 4)
Page 84: SECTION 4953 January 1990 Page 5 3)

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