EC&M’s Electrical Calculations Handbook - Chapter 7 potx

... enough equipment-grounding conductors, as shown in Fig. 7- 4 . Since system grounding is done at the service-disconnect- ing means, the equipment-grounding conductor and the neu- tral (“grounded”) ... such as a 460-volt (V), three-phase, three-wire delta system, an arc- ing fault that repeatedly restrikes can cause voltage “jack- ing” of up to six times the normal system phase-to-neutral vol...

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... ∠ 10°) See Fig. 3-4 for a further illustration of this calculation. 74 Chapter Three 0. 576 -j 0. 17 = (0. 576 ) 2 + (0. 17) 2 ARCTAN (-0 . 17/ 0. 576 ) ARCTAN (-0 .2951) 0.36 07 0.6 -1 6.4 ° 1. Change ... downward to Ϫj would be at an angle of ϩ 270 °, or Ϫ90°. Mathematics 75 0. 576 -j 0. 17 = (0. 576 ) 2 + (0. 17) 2 ARCTAN (-0 . 17/ 0. 576 ) ARCTAN (-0 .2951) = 0....

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... 75 90 2 1-2 5 7 0 -7 7 1.08 1.05 1.04 2 6-3 0 7 8-8 6 1 1 1 3 1-3 5 8 7- 9 5 0.91 0.94 0.96 3 6-4 0 9 6-1 04 0.82 0.88 0.91 4 1-4 5 10 5-1 13 0 .71 0.82 0. 87 4 6-5 0 11 4-1 22 0.58 0 .75 0.82 5 1-5 5 12 3-1 31 0.41 0. 67 0 .76 5 6-6 0 ... REMARKS 31 0-1 6 OR 31 0-1 7 31 0-1 6 OR 31 0-1 7 UNDERGROUND FEEDER CABLE 31 0-1 6 OR 31 0-1 7 MOI...

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... voltage. Short-Circuit Calculations 183 Step 4. The small contributions from the 20 0- and 40-hp 480-V motors, 1 376 kVA, are reduced to an even smaller val- ue by the 1000-kVA transformer to 1 275 kVA. Step ... electrical systems against damage during short-circuit conditions is required by the National Electrical Code (Secs. 11 0-9 and 11 0-1 0). Short-Circuit Calculations 18...

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... $892.28 (1 ϩ 0.08) 7 Ϫ 1 ᎏᎏ 0.08 (1 ϩ i) n Ϫ 1 ᎏᎏ i 418 Chapter Fifteen Figure 1 5-2 2 Solve for the present value P of maintenance costs over the 2 0- year life of the generators. 376 Figure 1 5-2 Switch ... receptacle device installation personnel hours. 377 Figure 1 5-5 Heavy-wall rigid-steel installation personnel hours. 383 neering economic studies. A cash-flow diagra...

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... Conductors 170 Conductor and Cable Selection 170 Chapter 5. Short-Circuit Calculations 179 Sources of Short-Circuit Current 182 The Ability of the Electrical Utility System to Produce Short-Circuit ... characteristics 4-2 2 Heat losses of a copper bar from its dimensions and ampere load 8-1 Horizontal footcandle value using point method 4-1 1 Impedance of 600-V, 5-kV, and 15...

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... Volt, 3-phase 4-wire wye Note 5 460 Volt, 3-phase 3-wire delta Note 4 600/3 47 Volt, 3-phase, 4-wire wye 2400 Volt, 3-phase, 3-wire delta 2400 Coltm 3-phase, 4-wire wye 4160/2400 Volt, 3-phase, 4-wire ... -j 104 = (180) 2 + (104) 2 Minus Phase b voltage - (120 120 ° = - 120 -6 0 ° ) = -( -1 20 COS 60 -j 120 SIN 60) = -[ (-1 20)(5) -j (120)(.866)] = -[ -6 0 +j 103.92...

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... power conductors and generator overcurrent pro- 200 Chapter Six Gas-turbine generators arrive at the installation site prepackaged on skids. Figure 6-2 Solve for generator overcurrent protection ... percent Generator Sizing Calculations 1 97 done to accommodate the lagging power factor of the loads, since quadrature-component currents do not require engine power because they do no wor...

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... necessary to use the point-by-point method. The Point-by-Point Method How to make point-by-point calculations Later in this chapter, lighting calculations within areas hav- ing reflective surfaces, ... footcandles from the second luminaire. Sample point-by-point lighting calculations Refer to Fig. 8-1 for sample point-by-point lighting calcula- tions for both the nadir point and a po...

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... Fig. 9-1 2 on p. 278 . A sample calculation using this table is shown in Fig. 9-1 3 on p. 279 . Transformers 273 Figure 9-9 The transformer output voltage can be adjusted by switching to dif- ferent ... transformer coil. 272 260 Figure 9-1 0 Table replicating part of NEC Table 45 0-3 (a), overcurrent protec- tion of transformers over 600 V. 274 Figure 9-1 2 Table replicati...

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