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3.2.8.2. construction temporarily power supply
From;    Author:Stand originally

The 2nd chapter? Construction temporarily power supply


1? Calculate example with coulombmeter
? ? ? [Case 1A428021]
? ? ? (1) setting? ? ?
? ? ? Have 4 multilayer residential project, every 340 ㎡, aggregate 13612 ㎡, before construction, the cop outdoor all puts through to village artery. Right when the organization that undertakes construction prepares is designed the establishment that use phone undertakes designing. Decorate according to plane, the establishment that use phone is as follows:
? ? ? Tower type crane 2, 2 = of 36 × 72kW; 400L mixer 2, 2 = of 10 × 20kW; 30t windlass 2, 2 = of 7.5 × 15kW; Vibrator 3, 3 = of 3 × 6kW; Frog rammer 3, 3 = of 3 × 9kW; The 30kW such as electric saw, electric planer; Electric welder 2, 2 = of 20.5 × 41KVA; Illume uses phone, 25kW.
? ? ? (2) problem
? ? ? 1) is elaborated calculate theory with coulombmeter.
? ? ? 2) is calculated this exemple uses n.
? ? ? (3) analysis and solve
? ? ? 1) expounds theory of the computation that use phone:
? ? ? Building site temporarily the preparative work of power supply basically has: Be nodded with electric ground certainly and use n, choose power source, determine the power of the form of power supply system and transformer substation, amount, decision lead is sectional decorate with circuit.
? ? ? Always use n to be able to press the following and formulary computation:

In type? ? P -- power supply equipment always needs a capacity (KVA) ;
? ? ? ? ? ? P1 -- electromotor rated power (KW) (bear of computation of have rendered great service) ;
? ? ? ? ? ? P2 -- electric welder nominal capacity (KVA) (without result computation bear) ;
? ? ? ? ? ? P3 -- indoor illume capacity (KW) ;
? ? ? ? ? ? P4 -- capacity of the illume outdoor (KW) ; ?
? ? ? ? ? ? Cos φ -- the average power factor of electromotor (in construction site highest for 0.75 ~ 0.28, it is 0.65 ~ 0.75) commonly;
? ? ? ? ? ? Kl, K2, K3, K -- need coefficient, the inhomogenous coefficient when working at the same time namely, refer to a watch 21.


? ? ? 2) computation uses n;
? ? ? 1.05 × of P = (152 / of 0.6 × 41 25)=179.76kVA of 0.75 0.6 ×
? ? ? Choose SLl200 / 10 model 3 step-down transformer, nominal capacity 200 KVA.
2? Distribution box is decorated choose example with lead
? ? ? [Case 1A428022] ? ? ?
? ? ? (1) distribution box decorates a requirement
? ? ? It is the regulation of some group company below, also be " the safe technology that construction site uses phone temporarily is normative (JGJ46, 88) " general requirement:
? ? ? 1) metal box is worn, not box door, installing plate, electrified metal crust and the metal that approach live part protect column to wait, all need to use green yellow double color lead of many soft insulation / (the unified mark that protects 0 lines is green / Huang Shuang lubricious line, the for love or money forbids to use green yellow double lubricious line to make bear line) protect 0 lines with PE (0 lines cent is the job 0 lines N and protect 0 lines PE) make reliable connection.
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