Second Year, Fourth Quarter Practice Exam - Lessons 228 to 234, 2017NEC

10AWG 208V 1ø 2hp FLC = 13.2A x 1.25= 16.5A => 14AWG DETD 13.2A x 1.75 x 1.25 = 28.875‬ => 30A Fuse => Fuse <60A => 10AWG EGC

A 2-pole breaker in a 120/208-V, 3-ph, 4-W panel supplies power to a circuit. This circuit uses the smallest permitted conductors and is connected to a 2 hp, 208-V, 1Ø motor. A safety switch is to be installed adjacent to the motor. DETD fuses with a maximum permitted rating were installed in the switch. 430.52(C)(1) Exc. 1 was used to size these fuses. The minimum size EGC permitted is ___ AWG for this installation.

350 NEC 430.28 taps over 25 feet must (3) Have an ampacity not less than the feeder conductors

Although only 3 motors are shown, the feeder and the feeder OCPD were installed to supply power to (future) additional motors. The motor circuits are tapped in the gutter and the tap lengths are: Motor #3 - 12 ft Motor #2 - 23 ft Motor #1 - 51 ft. The minimum tap conductor size for Motor 1 would be ___ AWG or kcmil, as determined from the information provided above in Figure 234.155.

III

Among the terminal box (peckerhead) connection drawings shown in Figure 229.215, Diagram ___ is correctly drawn for a 9-lead, wye-wound, dual-voltage motor connected to high (480V) voltage.

I and II only

Heaters are installed in motor starters to protect ___. I. the motor against overload II. the branch circuit conductors against overload III. the motor against short circuits and ground faults

18.6

Refer to the nameplate shown in Figure 230.122. This motor should draw ___ amps at rated voltage when connected to Circuit 4-6-8 that is fed from a 3-pole breaker in a 120/240-volt, 3Ø, 4-wire panelboard.

15hp 3ø 460v FLC = 21 x 1.25 = 26.25 => 10AWG

Refer to the nameplate shown in Figure 230.128. The branch circuit for the motor is supplied from a 277/480-volt, 3Ø, 4-wire panelboard. The minimum size branch circuit conductors for the motor are ___AWG.

rotor

The ___ is the rotating part of a 3Ø motor.

T.430.247

The current from ___ is used to determine the branch circuit conductor size for a DC motor.

M1 20hp @208v FLC = 59.4 M2 30hp @208v FLC = 88 M3 50hp @208v FLC = 143 143 x 2.5 = 357 + 88 + 59.4 = 547.4, round down = 500A

Refer to the information shown in Figure 234.144. The breaker is in a 120/208-volt, 3Ø, 4-wire panel. The breaker is permitted to have a rating not greater than ___ amps where the feeder conductors are as small as permitted.

1/0

Refer to the information shown in Figure 234.144. Where the 3-pole breaker is in a 277/480-volt, 3Ø, 4-wire panel, the smallest feeder conductors permitted between the breaker and the wireway are ___ AWG.

100 175% x 59.4A x 125% = 92.8 => round up to next standard size fuse =>100 amp

Refer to the nameplate and information shown in Figure 230.131. The maximum size DETD fuses permitted are ___ A.

20hp 3ø 460v FLC = 27A x 1.25 = 33.75 => 10AWG

Refer to the nameplate and information shown in Figure 230.132. The smallest BC conductors permitted are ___ AWG.

7.5hp 3ø 208v FLC = 24.2A x 1.25 = 30.25 => T400.5A1 = 8AWG

Refer to the nameplate in Figure 230.127. The branch circuit for the motor is supplied from a 120/208-volt, 3Ø, 4-wire panelboard. What is the minimum size (3 wire + ground) SO cord that could be used as a flexible connection for the motor?

Neither I nor II 3ø switches cant be used on 1ø motors

A 3Ø safety switch that is rated at ___ volts can be used as the disconnecting means for a 208-volt, 1Ø motor.

80A 10hp 1ø motor FLC is 25A @ 460v, 50% of the 50A in the 230V Column FLC from T430.248 25A x 125% = 31.25A 31.25A x 250% for ITCB = 78.125‬A 80A next standard size up

Refer to Figure 230.223. An ITCB with a maximum rating of ___ A is the largest permitted to be used for the branch circuit OCPD.

12

Refer to Figure 230.271. Between the panel and the wireway, the minimum size circuit conductors for Motor #4 are ___ AWG. Count the number of circuit conductors in the conduit and determine ampacity inside the conduit from the 90º column.

Neither I nor II

Refer to Figure 232.103. ___ could be used as a disconnecting means for a 5 horsepower, 240-volt, single-phase motor.

80 3hp motor 34A FLC @ 115v from Table 430.248 34A x 125% = 42.5A Max DETD fuse size from Table 430.52 is 175% 42.5 × 175% =‬ 74.375 Amps => 80A Fuse ( Next standard size)

Motor Nameplate Information: 115/230-V 1Ø 3 hp Supply: 1-pole breaker in a 120/240-V, 1-ph, 3-W panel The maximum size DETD fuses permitted are ___ A.

6

Motor Nameplate Information: 115/230-V 1Ø 5 hp Supply: 2-pole breaker in a 120/240-V, 1-ph, 3-W panel Minimum size circuit conductors are ___ AWG.

8AWG T430.250 10hp FLC = 28A x 1.25= 35A => 10AWG T430.52 250% ITCB 28A x 1.25 x 2.5 => 87.5A => 90A T250.122 OCPD <100A => 8AWG

Refer to Figure 230.121. When the maximum permitted size ITCB has been installed for the branch circuit [using 430.52(C)(1) Exc 1] and the smallest permitted circuit conductors are installed, the smallest size EGC permitted is ___ AWG.

M1 230V 1ø 5hp FLC = 28A x 1.25= 35A => 10AWG T430.52 250% ITCB 28A x 1.25 x 2.5 => 87.5A => 90A T250.122 OCPD <200A => 6AWG

Refer to Figure 230.261. The smallest EGC that can be installed between the safety switch and Motor #1 is ___ AWG.

II

The motor winding leads in Drawing ___ (shown below) are correctly numbered.

40 amps

Refer to Figure 234.412. The maximum size circuit breaker that you are permitted to use for the branch circuit is ___ amps.

12 AWG MCA is already built in with 125% ampacity for the largest motor

Refer to Figure 234.412. The minimum size wire that you are permitted to use for the branch circuit is ___ AWG.

4 AWG cma= KIL(1.732) ÷ Vd => (10.86)(40)(160)(1.732) = 120.380 ÷ 3 = 40,126 kcmil or larger

Refer to the information shown in Figure 230.230. The motor is located 160 feet from the panelboard and the specifications limit the voltage drop to 3% at this motor. Use K=10.86 and nameplate current to determine the proper size wire to satisfy the specs. Use cma = KIL(1.732) ÷ Vd

D = p1; t8,p2,t3; t4,t2,t5

Refer to the nameplate from a 115/230-volt motor shown above in Figure 228.203. The motor leads have been terminated on a terminal strip. T-strip connections from a 120-volt supply circuit are correctly shown at ___ (below).

2 350 kcmil = 310A x ⅓ = 103⅓A => 2AWG NEC 430.28 taps < 25 feet but > 10 ft Have an ampacity of at least one-third that of the feeder conductors

The motor circuits are tapped in the gutter and the tap lengths are: Motor #3 - 12 ft Motor #2 - 23 ft Motor #1 - 51 ft.The minimum tap conductor size for Motor 3 would be ___ AWG or kcmil, as determined from the information provided above in Figure 234.155.

240

The nameplate of a 460-volt, three-phase motor shows an FLA of 40 amps. It will draw about ___ amps if one leg is dead when the motor tries to start. This is a fairly typical motor that has a locked-rotor current of about six times running current.

synchronous

The speed of the rotating magnetic field in the stator of an AC motor is referred to as the ___ speed.

Torque

___ is the turning force exerted on the armature in a motor.