2nd Year-Quarter 3 exam

Scenario 221.12 A voltmeter is used to measure voltages between various points on a 120/208-volt, 3Ø, 4W system. Refer to Scenario 221.12. ___ volts will be read between neutral and ground .a. 208 b. 120 c. 0 d. 277 e. 240

0

In a 240-volt ungrounded delta, what is the voltage between the B phase and ground? a. 240 volts b. 120 volts c. 0 volts d. 360 volts e. 208 volts

0 volts Dead mans leg in ungrounded deltas

Individual dry-type transformers rated over 112.5 kVA shall be enclosed in a fire-resistant room with materials having a ___-hour minimum fire rating. a. 2 b. 3 c. 6 d. 1

1

Two THHN/THWN copper circuit conductors are connected to the neutral bar and a 1-pole breaker in a 277/480-volt, 3Ø, 4-wire panelboard. The circuit serves a load that draws 11.9 amps. The distance between the panel and the load is 176 feet. The smallest conductors you can install to the load are ___. The specifications limit the voltage drop to 2.1%. Use K = 10.86 to solve this problem. a. 12 b. 14 c. 8 d. 10 e. 6

10

A three-phase motor draws 28 amps at 230 volts. The power used by the motor is ___ KVA. a. 8.050 b. 8.214 c. 13.943 d. 10.411 e. 11.154

11.154 P=I*(E*1.732) 28*(230*1.732)=11,154 11,154/1,000=11.154

A particular load has a nameplate rating of 31.2 amps at 120 volts. The circuit you have available to supply the load is 100 volts. The catalog number for a B-B transformer that can operate the load at its rated voltage is ___. a. 21105 b. 11106 c. 21107 d. 11105 e. 21106 f. 11112

11106

Two 10 AWG THHN/THWN stranded uncoated copper conductors are installed in 193 feet of conduit from a 120/240-volt, 3Ø, 4-wire panelboard to a load. The load is rated to draw 13.6 amps when operated at 120 volts. What is the voltage applied to the load? Use Ohm's Law and NEC® Table 8 resistance values. a. 113.5 b. 120 c. 6.1 d. 116.7 e. 117.5

113.5

Voltage Drop Scenario #1For a load, the conductors consist of two 12 AWG THHN/THWN solid coated copper conductors connected to the neutral bar and a 1-pole breaker in a 120/208-volt, 3Ø, 4-wire panelboard. The circuit serves a load that draws 9.8 amps. The distance between the panel and the load is 150 feet. Refer to Voltage Drop Scenario #1. Use NEC® Table 8 resistance and Ohm's Law to find the voltage dropped in the conductors and then determine the voltage applied to the load. The voltage applied to the load is ___ volts. a. 117.1 b. 119.6 c. 202.6 d. 114.1 e. 202.1

114.1 .00201*(150*2)=.603 ohms 9.8 amps*.603=5.9 volts 120-5.9=114.1

The ampacity of conductors from the generator to the first distribution device(s) containing overcurrent protection shall not be less than ___ percent of the nameplate current rating of the generator. a. 150 b. 115 c. 200 d. 125

115

Two THHN/THWN copper circuit conductors are connected to a 2-pole breaker in a 120/240-volt, 3Ø, 4-wire panelboard. The circuit serves a load that draws 13.7 amps. The distance between the panel and the load is 95 feet. The smallest conductors you can install to the load are ___. The specifications limit the voltage drop to 2.4%. Use K = 11.2 to solve this problem. a. 8 b. 14 c. 12 d. 6 e. 10

12

A 480 — 240-volt 3-wire transformer is delivering power to a 3Ø load and has 75 amps of coil current flowing through each winding. The current flowing in each circuit conductor to the load is ___ amps. a. 25 b. 43.3 c. 129.9 d. 75

129.9 I(line)=I(coil)*1.732 75*1.732=129.9

Voltage Drop Scenario #1For a load, the conductors consist of two 12 AWG THHN/THWN solid coated copper conductors connected to the neutral bar and a 1-pole breaker in a 120/208-volt, 3Ø, 4-wire panelboard. The circuit serves a load that draws 9.8 amps. The distance between the panel and the load is 150 feet. Refer to Voltage Drop Scenario #1. Use the formula K = (Rper foot x cma) to determine the actual K value. The actual K value = ___ using NEC® Table 8. a. 12.6 b. 13.13 c. 12.0 d. 13.39 e. 12.93

13.13 Using Table 8, Ch. 9 2.01/1,000=.00201 .00201*6530=13.13

A 3Ø transformer bank supplies 120/240 volts to a 3Ø, 4-wire panelboard. There is a 30 kVA 3Ø load connected to a 3-pole breaker in spaces 1-3-5. There is a 240-volt 15 kW load connected to a 2-pole breaker in spaces 2-4. There is a 120-volt 10 kW load connected to a 1-pole breaker in space 6. Refer to Scenario 220.21. If all the loads are operating and a clamp-on ammeter were placed around the AØ feeder conductor to the panel, there should be ___ amps of current flowing in the feeder conductor.

134.7

Refer to Figure 221.404. The voltage applied to Heating Element B is ___ volts. a. 360.3 b. 240 c. 415.7 d. 208 e. 138.6

138.6 240/1.732=138.6 Refer to Figure 221.404

From Y2 - Annex D, you have selected a catalog number 31105 transformer to boost the available circuit voltage from 437 to 480 volts to serve a 480-volt load. The supply circuit originates in a 277/480-volt, 3Ø, 4-W panelboard but is 437 volts due to the excessive length of the circuit. The largest breaker permitted by the NEC® for this circuit is a 2-pole ___ A. a. 10 b. 30 c. 20 d. 25 e. 15

15

Refer to Figure 221.402. If A meter 2 indicates 38.5 amps, the generator is delivering ___ kW of power. a. 13.87 b. 6.23 c. 16.0 d. 8.01 e. 9.24

16 P=I*(E*1.732) 38.5*(240*1.732)=16,003 16,003/1,000=16 Refer to Figure 221.402.

A 225 KVA transformer has a 120/240-volt, 4-wire delta secondary. The nameplate shows 3.2% Z. The available secondary bolted (line-to-line) fault current is ___ amps. a. 29,297 b. 19,517 c. 5,413 d. 7,200 e. 16,915

16,915 225,000/(240*1.732*.032)=16,915

A 3Ø load is connected to the secondary of a - transformer that has a 12,470-volt primary and a 480-volt secondary. When the secondary conductors to the load are carrying 456 Amps, the primary line conductors are carrying ___ Amps. a. 10.13 b. 17.55 c. 52.65 d. 87.76 e. 152

17.55 12,470:480(voltage ratio) 25.98:1(voltage ratio) 1:25.98(Current ratio) 1/25.98*456=17.55

An open-delta bank of transformers uses 100 KVA transformers. This bank can deliver a maximum of ___ kVA of power. a. 200 b. 173 c. 115 d. 87 e. 300

173 P(3phase-open delta)=P(1phase*2)*(1.732/2) (100*2)*.866=173.2

A 3Ø load is connected to the delta-connected secondary of a transformer. The transformer has 102 amps of current flowing in each secondary winding. Between the load and the transformer, ___ amps of line current is flowing in the conductors. a. 59 b. 177 c. 198 d. 102 e. 306

177 I(line)=I(coil)*1.732 102*1.732=176.6 or 177

A "bank" of three 1Ø transformers has a total rating of 60 KVA. This means that each of the transformers is rated to deliver ___ KVA. a. 60 b. 20 c. 30 d. 15

20 60 KVA/3=20

Scenario 220.53The secondary of a 300 KVA transformer delivers power to a 180-amp, 3Ø load. This is a 480 — 240 volt - transformer. Primary and secondary conductors are the minimum size required to serve the load. Refer to Scenario 220.53. The secondary OCPD can have a rating no greater than ___ amps. a. 100 b. 150 c. 200 d. 175 e. none of these

200 Use Table 240.6(A) in NEC to find the next size up from 180 amps

Refer to Figure 225.102 and the information in Y2 - Annex D for a 3.0 KVA Buck-Boost transformer. Panel K is 120/208V 3Ø, 4-W. The Control Panel requires 240 volts. The Catalog number for this transformer is ___. a. 1304 b. 21110 c. 31110 d. 11110 e. none of these

21110

The supply circuit shown in Figure 225.104 is from a 2-P breaker in a 120/208-V, 3Ø, 4W panel. The foreign-made equipment is rated to operate at 220 volts. The supply-circuit voltage is 206 volts where it enters the B-B transformer. If Connection Diagram G, from Y2 - Annex D, is used to connect a Group II transformer, the equipment will be supplied with ___ volts. a. 220 b. 230 c. 233 d. 216 e. 240

220 Refer to Figure 225.104

Refer to Y2 - Annex D and Figure 225.102. Panel K is 120/208V, 3Ø, 4-W. The Control Panel requires 230 volts. Where the proper connections are made and the input voltage is exactly 208 volts and a 3.0 KVA, GROUP I transformer is used, the calculated voltage that would be applied to the Control Panel is ___ volts. a. 236 b. 231 c. 240 d. 219 e. 229

229 Refer to Figure 225.102 and Y2 Annex D

Refer to Figure 225.102 and the information in Y2 - Annex D for a 3.0 KVA Buck-Boost transformer. Panel K is 120/208V, 3Ø, 4-W. The Control Panel requires 240 volts. Using a GROUP II transformer, assuming the proper connections are made and the input voltage is exactly 208 volts, the calculated voltage that would be applied to the Control Panel is ___ volts. Select one: a. 240 b. 236 c. 219 d. 229 e. 231

236 Refer to Figure 225.102 and Y2 Annex D

A single-phase, 480-volt, 9600-watt water heater is incorrectly connected to a 240-volt circuit. How much power will be used? a. 2400 b. 1732 c. 1386 d. 4157 e. 9600

2400 R=E^2/P 480^2/9600=24 I=E/R 240/24=10A P=I*E 10*240=2400

Refer to Figure 221.403. The voltage applied to Motor Winding B is ___ volts. a. 480 b. 240 c. 120 d. 277 e. 208

277 Refer to Figure 221.403

A liquid-filled transformer has a primary voltage of 12,470 volts. The transformer is surrounded by a 6-foot-high fence. The overall height of the fence must be extended 1 foot with at least ___ strands of barbed wire on top of the fence. a. 3 b. 1 c. 2 d. no minimum required

3

Transformer vaults shall be constructed of materials with a minimum fire resistance of ___ hours. a. 6 b. 2 c. 4 d. 3

3

A 90-amp breaker supplies power to a 75 KVA 480 - 120/208-volt,3Ø, 4-W transformer. The transformer feeds a panelboard with a 200-amp main breaker. The length of the secondary conductors between the transformer and the main is 19 feet. These conductors must be at least ___ AWG in size. a. 2/0 b. 4 c. 3/0 d. 4/0 e. 3 f. no minimum

3/0

One set of secondary conductors is connected to Safety Switch #1. The feeder conductors in the wireway are protected by the fuses in Switch #1. Taps are made in the wireway (gutter) to supply power to the MBO panels and Safety Switches #2 & #3. Refer to the indoor installation shown in Figure 223.503. The smallest wires that can be connected to the transformer primary are ___ kcmil or AWG. a. 300 b. 1/0 c. 3/0 d. 2/0 e. 250

3/0

A utility overhead distribution system operates at 34,500 volts. This would be equal to ___ kV. a. .345 b. 34.5 c. 3.45 d. 345 e. none of these

34.5

The maximum size fuse permitted by Note 1, to NEC® Table 450.3(A), to protect the primary of a 4160 to 480-V, 3Ø, 75 KVA transformer is ___ amps. The transformer has an impedance of 1.7% and is installed in a nonsupervised location. a. 60 b. 70 c. 35 d. 20 e. 30

35 75,000/(4,160x1.732)=10.4amps 10.4x3=31.2amps Next size up is 35

The neutral is bonded to the frame and connected to a ground rod near a 3Ø, 4-wire 120/208-volt optional standby generator. The transfer switch supplying power to a building system from this generator is required to have ___ poles. a. 3 b. 2 c. 4

4

A 225 KVA 480 - 120/208-volt,3Ø, 4-W transformer feeds a panelboard with a 225-amp main breaker. The length of the secondary conductors between the transformer and the main is 9 feet. These conductors must be at least ___ in size where the primary breaker is 300 Amps. a. 1 AWG b. 1/0 AWG c. 4 AWG d. 4/0 AWG e. none of these

4/0 AWG

A bank of three 100 KVA transformers is delivering 120/240 volts to a building service. This bank can deliver ___ amps of current to the service if one of the transformers goes out. a. 722 b. 417 c. 833 d. 200 e. 481

417 P(3phase-open delta)=P(1phase*3)*.577 (100*3)*.577=173.1KVA 173,100/(240*1.732)=416.67 or 417

Refer to Figure 221.403. Each of the Motor Windings (A, B, and C) is rated at 15 kVA. The total 3Ø rating of the motor must be ___ KVA. a. 15 b. 26 c. 5 d. 45 e. 8.66

45 15*3=45 Refer to Figure 221.403.

Refer to Figure 219.102. Each circuit conductor feeding the load connected to Circuit LB-6,8 will carry ___ amps. a. 48.6 b. 24.3 c. 42.1 d. 28.0 e. 84.2

48.6 10,100KVA/208V=48.6A

A 480-volt 3-phase circuit is connected to the delta primary of a 480 to 240-volt 3-phase transformer. The voltage across any one primary winding is ___ volts. a. 480 b. 120 c. 277 d. 208 e. 240

480

Refer to Figure 221.401. The voltage applied to Heating Element B is ___ volts. a. 277 b. 120 c. 208 d. 480 e. 240

480 Refer to Figure 221.401

You have a 208-volt circuit available to supply a 230-V, 175 A load. The rating for a B-B transformer that can operate the load at its rated voltage is ___ KVA. a. 75 b. 2.0 c. 5.0 d. 1.5 e. 7.5 f. 3.0

5.0 ((230-208)/240x175)/1000

The circuit you have available to supply a 240-V, 150 A load is 208 volts. The rating for a B-B transformer that can operate the load at its rated voltage is ___ KVA. a. 1.5 b. 5.0 c. 7.5 d. 3.0 e. 2.0 f. 37.5

5.0 ((240-208)/240x150)/1,000

For transformers smaller than 3 KVA with no load connected to the output leads, the output voltage can be expected to be about ___ the nameplate rating a. double b. 6% higher than c. 15% lower than d. half

6% higher than

The maximum size ITCB permitted to protect the primary of a 4160 to 480-V, 1Ø, 75 KVA transformer is ___ amps, as required by NEC® 450.3. The transformer has an impedance of 4.3% and is installed in a supervised location. Secondary protection is NOT required. a. 35 b. 45 c. 60 d. 70 e. 30

60 75,000/4160=18.03amps 18.03x3=54.1A Next size up is 60 NEC Article 450.3(A)

Emergency systems are covered by the NEC® in Article ___. a. 695 b. 692 c. 690 d. 700

700

Refer to Figure 221.401. If the nameplate rating of the 3Ø duct heater is 60 KW at 480 volts, A meter 2 will indicate ___ amps at the applied voltage. a. 375 b. 217 c. 42 d. 125 e. 72

72 I=P/(E*1.732) 60,000/(480*1.732)=72 Refer to Figure 221.401

A transformer has a 120/208-volt wye secondary. If the current in each of the secondary coils (or windings) is 75 amps, what is the secondary line current? a. 43 amps b. 130 amps c. 75 amps d. 0 amps e. 225 amps

75 amps I(line)=I(coil)

A fused safety switch feeds a 480 to 208Y/120-volt, 3Ø, 30 KVA transformer. The transformer supplies power to a 3Ø 100-amp main breaker panelboard. According to NEC® 450.3, the fuses in the safety switch are permitted to be not larger than ___ amps so that the transformer is adequately protected against overload. a. 1100 b. 1000 c. 90 d. 80 e. 150

90 30,000/(480x1.732)=36.1amps 36.1x2.5=90.25 or 90amps

A 240-volt 3Ø load is to be supplied from a 208-volt, 3Ø, 3-wire circuit. You will have to boost the circuit voltage to supply rated voltage to the load. Refer to Y2 - Annex D and Scenario B-B 1 to answer this question. You should make your field connections using connection diagram ___. a. C-C b. A-A c. B-B d. G-G e. F-F

B-B

Refer to Table 221.1. Which secondary conductor to the panel carries the least current? a. AØ b. BØ c. CØ

BØ Refer to Table 221.1.

Refer to Figure 225.102 and the information from Y2 - Annex D for a 3.0 KVA Buck-Boost transformer. The Control Panel requires 230 volts. Panel K is 120/208V 3Ø, 4-W. Using a B-B transformer from the appropriate Group, you should make your connections as shown in Connection Diagram ___. a. H b. I c. E d. G e. none of these

H Refer to Figure 225.102 and Y2 Annex D

Which connection diagram, shown in Figure 224.108, should be used where the Supply Circuit is from a 1-pole breaker 120/240-volt, 3-ph, 4-W panelboard? The load is rated to operate at 12 volts. The transformer is a 120 x 240 — 12/24 volt. a. I b. II c. III d. IV e. none of these

I Refer to Figure 224.108

Which of the following loads are considered to be non-linear? I. computers II. HID lighting III. electronic ballasts a. II only b. I, II & III c. II & III only d. I & II only e. II only

I, II & III

Which of the illustrations shown in Figure 210.1 would satisfy the Code requirements of 240.22(1)? a. I or III only b. II only c. I only d. III only e. I or II or III f. none of these

II only Refer to Figure 210.1

Which connection diagram, shown in Figure 224.108, should be used where the Supply Circuit is from a 2-pole breaker 277/480-volt, 3-ph, 4-W panelboard? The load is rated to operate at 48 volts. The transformer is a 240 x 480 — 24/48 volt. a. I b. II c. III d. IV e. none of these

III Refer to Figure 224.108

Which connection diagram, shown in Figure 224.108, should be used where the Supply Circuit is from a 1-pole breaker 120/240-volt, 3-ph, 4-W panelboard? The load is rated to operate at 32 volts. The transformer is a 120 x 240 — 16/32 volt. a. I b. II c. III d. IV e. none of these

IV Refer to Figure 224.108

A 480-volt to 240-volt three-phase transformer is rated for 112.5 KVA. The transformer serves an existing 3Ø load of 190 amps. Would a three-phase load of 54 amps cause an overload? a. Yes b. No

No I=P/(E*1.732) 112,500/(240*1.732)=270.6Amps 270.6-190=80.6 80.6-54=26.6Amps remain

Generator starting batteries should be ___. a. located close to the generator set to keep cables short b. in a clean, dry, and stable temperature location c. provided with easy access to battery caps for checking electrolyte levels d. all of these

all of these

Selection criteria considerations for generators include ___ requirements. a. full load b. fuel source c. voltage d. isolation pad e. all of these f. none of these

all of these

Which of the following would be considered non-linear loads? a. welders b. desktop computers c. AC variable speed drives for motors d. all of these

all of these

Three individual 240 x 480 -120/240 volt 2 KVA single-phase transformers could be connected to produce which of the following outputs? a. 120/208 volt 3Ø, 4-wire b. 120/240 volt 3Ø, 4-wire c. 240 volt 3Ø, 3-wire d. any of these

any of these

A piece of equipment has arrived at the job and its nameplate indicates that it is rated to operate at 230 (not 240) volts. You have already run a 2-wire circuit from a 2-pole breaker in a 120/208-volt, 3Ø, 4W panelboard to supply the equipment. You should connect the equipment ___. a. through a 120/240-16/32 Buck-Boost transformer b. through a 120/240-12/24 Buck-Boost transformer c. directly to the circuit

b. through a 120/240-12/24 Buck-Boost transformer

To deliver adequate fuel to diesel-fueled generator sets, without clogs and without injecting air into fuel lines, ___ piping is used for the fuel lines. a. galvanized steel b. black iron c. plastic d. nylon e. copper

black iron

Which of the following are non-linear loads? a. HID lighting b. variable frequency motor drives c. both a and b d. neither a nor b

both a and b

The output rating of generators is given on the nameplate in ___. I. KVA II. KW a. I only b. II only c. either I or II d. neither I nor II

either I or II

Day tanks can supply up to ___ of fuel to the generator unit. a. four hours b. 60 seconds c. 10 minutes d. 2 days e. none of these

four hours

A wye-connected transformer secondary has a line-to-neutral voltage of 277. The line-to-line voltage is ___ volts. a. 0 b. 208 c. 240 d. 277 e. none of these

none of these

Small transformers (less than 3 KVA) have high transformer regulation. Voltage regulation means ___. a. the output voltage is metered and adjusted with internal circuitry b. the rated output voltages are limited by federal regulation c. the output voltage drops when a load is connected

the output voltage drops when a load is connected

A 3Ø, 230-volt load is to be supplied with a 3Ø, 3-wire circuit that originates from a 120/208-volt, 3Ø, 4-w panelboard. As a minimum you will be required to install ___ Group I "buck-boost" transformer(s). Refer to Y2 - Annex D. a. three b. two c. one

two