electricity (single phase vs three phase)

8/20/2019 Electricity (single phase vs three phase)

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Electricity is either connected in single phase or three phase. In single phase, wire is

connected in phase to neutral with supplying 230 or 240 volts of electricity. Single phase

power is commonly used in households. While, in three phase, wire connected in phase to phase with supplying 400 volts of electricity. hree phase power is commonly used in

commercial premises.

In single phase! " # $Icos Ɵ

In three phase! " #$I cos Ɵ

Electrical wiring composes of electrical e%uipment such as ca&les, switch &oards, mainswitches, miniature circuit &rea'ers ()*+ or fuses, residual current devices (-*,

lighting points, power points, lightning arrestors, etc.. E/ample of a single phase

consumer electrical wiring is as shown in 1igure 3.2

1rom figure 3.2, we can see that 00m E*+ is connected to lighting general power

circuits, such as lamp, fan, motor (.. 5 irect n ine, alarm and air5conditioner.

While, 30m E*+ is connected to soc'et outlets.

3



irect n inehe irect n ine )otor Starter ( consist a )*+ or circuit +rea'er, contactor

and an overload relay for protection. Electromagnetic contactor which can &e opened &y

the thermal overload relay under fault conditions. has several &uilt5in protectivefeatures

(a Short5circuit protection

(& verload protection(c 6nder5votage protection

as !5

)ain circuit7"ower circuit



2 *ontrol *ircuit

verload protection for an electric motor is necessary to prevent &urnout and to ensure

ma/imum opeer rating life. 6nder any condition of overload, a motor draws e/cessive

current that causes overheating. Since motor winding insulation deteriorates due to



overheating, there are esta&lished limits on motor operating temperatures to protect a

motor from overheating. verload relays are employed on a motor control to limit the

amount of current drawn.



1or 8+ 39

oad )a/imum *urrent Estimate *urrent

1ilament ight (mount of the oad / "ower

-e%uired &y the oad / .: 7(230 / 0.:;

<<= of its ma/imum current

ight +ul& (mount of the oad / "ower

-e%uired &y the oad 7 230

<<= of its ma/imum current

Soc'et utlet

(S..>

(2 S..> / "ower -e%uired &y

each oad / ?alf the mountof the oad 7 230

00= / (2 S..> / "ower

-e%uired &y each oad 7 230@

40= / A)a/. *urrent5 00= /


each oadB 7 230

ir *onditioner (mount of the oad / "ower-e%uired &y the oad 7 (230 /

0.:;

Same as its ma/imum current

Water ?eater (mount of the oad / "ower


(00= / )a/. *urrent 7

mount of the oad@

(00= / )a/. *urrent 7

mount of the oad

@(2;= / )a/. *urrent 7 mount

of the oad

*oo'er *ontrol 6nit (mount of the oad / "ower


0 @ 30= / ()a/. *urrent 5

0



oad )a/imum *urrent Estimate *urrent

Soc'et utlet

(S..>


each oad / ?alf the mountof the oad 7 230

00= / (2 S..> / "ower

-e%uired &y each oad 7 230@

40= / A)a/. *urrent5 00= /(2 S..> / "ower -e%uired &yeach oadB 7 230

ir *onditioner C

)otor (3 phase

(mount of the oad /

"ower -e%uired &y

the oad 7 ( / 400 / 0.:;

00= / st ?ighest )a/.*urrent for each 6nit

@

:0= / 2nd ?ighest )a/.*urrent for each 6nit

@

<0= / Aotal )a/. *urrent of 3

phase oad 5 (00= / st?ighest )a/. *urrent for each

6nit 5 (:0= / 2nd ?ighest

)a/. *urrent for each 6nitB

3

electricity (single phase vs three phase)

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