GENERATOR SELECTION CONTENTS - Diesel Generator

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EXAMPLES OF <strong>SELECTION</strong> FOR VARIOUS LOAD CONDITIONS SECTION 4595 January 1990 Page 1 The following examples cannot hope to cover every possible calculation method, but they do demonstrate an approach for your guidance. Some are taken from actual enquiries whilst others are devised to demonstrate specific points. Example One This example was devised to consider many different load conditions simultaneously. The supply required is assumed to be 415V 3 phase 50Hz. LOAD DETAILS Single Phase 240V (a) 72 fluorescent light fittings each 100W and power factor corrected to 0.95 p.f. lag. (b) 7 heaters each requiring 20A. (c) 4 x 5 h.p. motors, started simultaneously Direct-On-Line (D.O.L.). Single Phase 415V (d) 5 welding sets each rated at 11A primary current 0.4 p.f. lag. Three Phase 415V (e) 3 x 3 h.p. machine tool motors started in sequence D.O.L. (f) 1 x 80 h.p. motor started by auto transformer at 80% tap but with a poor full load power factor of 0.6 p.f. lag. (g) 1 x 80kW motor started star/delta with a locked rotor current of 750A. LOAD ANALYSIS Now let us consider each load in turn. For the single phase loads ((a) to (d)) we shall calculate the ‘worst case’ single phase loading for each item and then multiply by 3 to obtain the equivalent 3 phase loading, (Section 4512). This assumes that one of the 3 phases always carries the highest single phase load of each item. This is unlikely to occur in practice as the total loads should be connected as balanced over the 3 phases as possible; however, it is a valid assumption for the purpose of a.c. generator sizing. LOAD (a) 72 fittings over 3 phases can be balanced at 24 fittings per phase. Steady State Transient Hence maximum single phase load is: There is no transient condition given for consideration 24 x 100 = 2.4kW (Section 4512) and 2.4 = 2.5kVA 0.95
LOAD (b) 7 Heaters over 3 phases means one phase must supply 3 heaters Steady State Transient Hence maximum single phase load is: There is no transient condition to consider 3 x 240 x 20 = 14.4kVA (Section 4512) 1000 From Section 4501, heaters can be assumed to run at unity power factor; hence load = 14.4kW LOAD (c) 4 motors over 3 phases means that one phase must supply 2 motors Steady State Transient Hence maximum steady state phase load is For the one phase with 2 motors starting given below. simultaneously, from Section 4522: SECTION 4595 January 1990 Page 2 From manufacturer’s data; 5 h.p. single phase D.O.L. Start Factor = 7.1 motor typical performance figures are: Hence Start kVA = D.O.L. Start Factor x h.p. rating. Efficiency = 0.78 p.u. rating. = 7.1 x 5 x 2 Power Factor = 0.8 p.f. lag = 71 kVA Steady State Load is: 2 x 5 x 0.746 = 9.6kW (Section 4512) 0.78 LOAD (d) and 9.6 = 12.0kVA 0.8 5 welding sets across one pair of 415V lines given a ‘worst case’ of one pair of lines having to supply 2 welding sets. Steady State Transient Hence loading is: No transient condition details are given for consideration 2 x 415 x 11 = 9.1kVA (Section 4512) 1000 and 9.1 x 0.4 = 3.6kW
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 48 and 49: LOAD (e) - 3 x 3 h.p. 3 phase motor
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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