GENERATOR SELECTION CONTENTS - Diesel Generator

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SECTION 4522 January 1990 Page 4 Whereas the star/delta system uses contactors and requires a 6 ends out motor winding to achieve a fixed, reduced voltage motor start; this method can be used with any type of motor and uses an auto transformer with fixed voltage taps along its winding. The basic idea is that a low line voltage is tapped off the auto transformer and fed to the motor on start. As the motor speeds up, the tap position is changed in any number of steps, increasing the line voltage until the full line voltage is directly across the motor terminals. Commonly used taps are 65% and 80% of full line voltage. Using the same form of calculation the following can be derived:- assume:- a.c. generator overload capability 2.5 p.u. motor start current 6.0 p.u. efficiency 0.9 p.u. Tap position 65% 80% 100% (as D.O.L.) Reduction in line starting voltage 35% 20% 0% Starting current is reduced to % of D.O.L. value 65% 80% 100% Starting kVA and staring torque are both required to % of D.O.L. value 42% 64% 100% Value of ratio S is 1.12 1.71 2.67 Again, as with the star/delta case, check that the full load motor run kW is less than the selected a.c. generator frame size kW rating, to ensure that the a.c. generator is capable of supplying the steady state continuous maximum running power requirement of the motor. For an example of a motor starting problem see Section 4595.
CONVENTIONAL MOTOR STARTING METHODS Throughout this discussion the following symbols will be used:- I = full load current of a a.c. generator at maximum rating. I M = running full load motor current. kW genr. = rated full load kW of a.c. generator kW M = rated full load shaft kW of motors S = ratio of a.c. generator kW requirement per kW motor rating. T M V L = starting torque required by motor. = line voltage. cos ∅ = load power factor. h M = motor efficiency. Direct-on-line (D.O.L) Starting SECTION 4522 January 1990 Page 1 In this case the full line voltage is switched directly to the motor terminals. The motor winding normally is connected delta. The maximum starting torque is available with this method, but a very high starting current is required. Assumptions:-starting current is 6 times motor full load current. N.B. Some motor manufacturers specify 7 or 8 times and any calculation would need the correct figures inserted; hence the earlier warning to obtain full technical details from the motor manufacturer (Section 4501). a.c. generator overload capacity is 2.5 p.u. Then under starting conditions: 2.51 ≥ 61 M From this we can derive a ratio of a.c. generator kW rating per kW motor rating.
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 44 and 45: Since I = kW genr. and I M = kW M _
Page 46 and 47: EXAMPLES OF SELECTION FOR VARIOUS L
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)

GENERATOR SELECTION CONTENTS - Diesel Generator

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