APPENDIX D
9.5 Diagram:
Total Computed Current
4ó0V3.Phæ,60H2
À
NID
Füs=
,*r
tI
ôr
I
b.TDFùs=60Àl
I
l*
I
bEler=
s IT
3004
d.rTDbMker= l00A
(B) Time Delay (TD) Fuses:
Largest TD fuse
Full load current of 20-Hp motor
Full load current of 1O-Hp motor
Total Computed
1
39.5ASettitrg
Co¡t¡ctor
14n¡¡f
14l Amperes
:
60 Amperes
:27
:
Current
Amperes
14 Amperes
:101
Amperes
Use 100 Amperes TD fuse.
(C) Inverse Time Delay (ITD) Breaker:
I
I
14 Amperes
Use 150 Amperes NTD fuse.
L
r
:
:
Full load current of 1O-Hp motor
Largest ITD
:
fuse
Full load current of 20-Hp motor
Full load current of l0-Hp motor
TWtim
Total Computed
90 Amperes
:27
:
Current :
Amperes
14 Amperes
131 Amperes
Use 125 Amperes ITD fuse.
Bxample D10
Motors, Motor Circuits, and Controllers, Multiple
Motors
Three squirrel cage induction motors: 25-Hp, 20-Hp
and 1O-Hp, all rated at460 volts, 3-phase, 60 Hz are to
be served by a feeder circuit. Ambient temperature does
Note: Only fuses and/or inverse time circuit breakers
are
allowed for this type of installation. [See Section 4.30.4.3(C)
(1)l
10.4 Diagram:
460V , 3-Phas,
60ltz
not exceed 30"C.
10.1 Total
b
Load: (See Table 4.30.14.4)
One 3-phase, 460 volts,
'-"'
motor
25-Hp
^^r
--
motor
One 3-phase, 460 volts, 10-Hp
motor
22 m¡rf
_
1A
:34
AmPeres
:
27 Amperes
:
14 Amperes
:
x0.25)
Net Computed
Current
8.5 Amperes
83.5 Amperes
10.2 Feeder Conductors: [See Table 3.10.2.6(BXi6)]
Use three 22mm2 THW wires.
10.3 Feeder Circuit Protection: [See
=
I 50A
tmA
t25À
TtÌw siræ
Búchciditttô¡kÊr¡
25-!fp 20tlp lGltp
Note 1: For single motor taps, refer to Section 4.30.4.3(D).
Note 2: (On Fire PumpApplication) For installations including
fire pumps, See Sections 2.30'6.3(A) Exception, 2.30.6.13(6),
2.30.7J(^) Exception No. 4, and2.30.7 .5 Exception No. 4.
ExamPle Dll
Voltage Regulatorso Single Phase, 60 Hlz, 165-280
Volts InPut, 230 Volts OutPut VR
Section
4.30.4.3(c)l
Largest Protective Device:
Determine the size of input feederwires and overcurrent
protection for a 5 kVA, l-phase, 60 hertz, 165-280 volts
input,230 volts output automatic voltage regulator.
The 25-Hp motor being the largest motor, has the largest
protective device. For the values of the different device,
5
Iu,-
see Example D9.
:
(A) Nontime Delay (NTD) Fuses:
LargestNTD fuse
Full load current of 20-Hp
TD
o
Mota tmsoll¿n
25o/o of Largest Motor (See Section 4.30.2.4)
34 Amperes
b.
II
l-_
One 3-phase, 460 volts, 20-Hp
fe
f r NTDfs
ITDbpta :
:
lO0Amperes
motor :27 Amperes
kVAx
165
1000
V
30 Amperes
Use 8.0 mmz (3.2 mm dia.) THW for feeder wire and
60-ampere fuse or 40-ampere trip molded case circuit
breaker.
I
053