3-1 Test Set

173 kva

A 100-kVA transformer of a 300-kVA wye-delta bank has failed. Power has been restored by converting the system to open wye-open delta. The power rating of the open bank has been reduced to ? .

86.6 kva

A 150-kVA closed transformer bank consists of three identical transformers. An internal fault has occurred in one of the units. As a temporary measure, the bank has been converted to an open-delta-open-delta. The capacity of the temporary bank is reduced to ? .

36 A

A 150-kVA transformer bank consists of three 50-kVA transformers connected in a delta-delta configuration. The primary nameplate voltage rating is 2,400/4,160 volts. With a balanced full load, each of the primary leads will carry ? .

271 A

A 225-kVA delta-wye transformer bank feeds a 480-volt secondary circuit. The secondary windings draw 271 amperes at full load. The current through each of the two X terminal to star point conductors is ? .

75%

A 3-phase line requires ? of the conductive material that is required by a single-phase line to transmit the same power over a fixed distance at a given voltage.

1 and a half times greater

A 3-phase motor will deliver ? power to a machine as a single-phase motor of the same size.

360 A

A 300-kVA delta-delta bank is operating at the 100% rating. The secondary is a balanced 480-volt, 3-wire load. The current through each load lead is ? .

361 A

A 300-kVA transformer bank with the secondary windings configured in wye feeds a balanced 480-volt load. At full load, or 100% of the power rating, the current through each of the secondary load lines is ? .

62.5 amps

A 450-kVAR capacitor bank is installed on a 4,160-volt wye line. The phase to ground voltage is 2.4 kilovolts. The capacitors draw a continuous current of ? .Use the formula in the textbook reference to solve for the current.

45 V

A 7,200-volt line has a drop of 90 volts between the source and end line customer. To deliver the same amount of power to the customer at 14,400 volts, the voltage drop would be ? .

90 A

A 75-kVA bank is constructed with three equally sized transformers. The secondary windings have a nameplate voltage ratings of 240/480 volts. The line-to-line voltage on the 3-wire secondary is 480 volts. With a balanced load, the current through each secondary lead is approximately ? .

90 A

A 75-kVA closed wye-delta transformer bank feeds a 3-wire, 480-volt load. When operating at full rated capacity, the current on each of the three load lines is ? . (Round the FINAL answer to the nearest whole number.)

Journeyman

A ? is a skilled tradesman who has completed a prescribed apprenticeship in a particular craft.

True

A Journeyman Electrical Worker's reputation will depend on his or her attitude and work ethic.

storing an electrical charge, making a correction to power factor, or providing voltage for timing circuits

A capacitor can perform a variety of tasks, including ? .

36 A

A closed 150-kVA delta-wye bank is connected to a 2,400-volt, 3-wire line. The three transformers are operating at full load. The current through the primary leads is ? . (Round the FINAL answer to the nearest whole number.)

30 KVA

A closed transformer bank supplies 240-volt, 3-phase and 120/240-volt, single-phase power. With a single-phase load of 30 kVA and a 3-phase load of 60 kVA, the total load on each of the power pots is ? .

60 kva

A closed wye-delta transformer bank supplies 240-volt, 3-phase and 120/240-volt, single-phase power. With a single-phase load of 45 kVA and a 3-phase load of 90 kVA, the total load on the lighter transformer is ? .

24 kva

A closed wye-delta transformer bank supplies 240-volt, 3-phase power and 120/240-volt, single-phase power on a 4-wire service line. If the single-phase load is 36 kVA, the transformer with the grounded X2 bushing will supply ? of that load.

True

A job steward needs to be familiar with the craft jurisdictions defined by contract language.

4- phase

A poly-phase electrical system having a 90° phase separation is the ? type.

7.2 kv

A single-phase tap take off from a 12.47-kilovolt, 3-phase wye line has a line-to-neutral voltage of ? .

False

A straight piece of wire carrying an AC current does not have inductance.

346 A

A substation transformer bank with a delta connected secondary has currents of 200 amperes through each of the secondary coils. The current flow through each of the load lines is ? .

65.7 kva

A three-transformer bank serves a mixed single- and 3-phase load at 120/240 volts. The clip-on ampere meter readings on the secondary are:A phase = 195 AB phase = 175 AC phase = 105 AThe total kVA bank load is ? . (Round the FINAL answer to one decimal place.)

True

A transformer bank provides 240-volt, 3-phase and 120/240-volt, single-phase power. A vector line drawing of the secondary shows the 208-volt wild leg is at the point farthest from the grounded X2 terminal.

157.5 A

A transformer has 7,200 volts across the primary and 480 volts across the secondary, and 10.5 amperes are flowing through the primary. The secondary current is ? .

Inductive

A transformer is an example of a(n) ? load that would cause low power factor.

312.5 A

A transformer rated at 75 kVA can carry ? at 240 volts.

In series

A typical distribution transformer provides 120/240 volts to residential customers and has its coils connected ? .

Henry

A unit of inductance is called a(n) ? .

24940 v

A wye system with a line-to-neutral potential of 14,400 volts has line-to-line potential of ? .

625 A

A wye-wye bank is built with three 75-kVA transformers. The voltage on the secondary mains is 208 volts from line-to-line. When operating at balanced full load, or 100% of the power rating, the current through each secondary leads is ? .

4

After determining which transformer is bad in a 3-phase bank, there are ? things to check for on the nameplate before calling for a new transformer.

True

After disconnecting capacitors from the energized lines, workers must wait a minimum of five minutes before shorting the terminals.

False

After the extensive training received during apprenticeship, advanced training is not required to remain competitive as a Journeyman.

False

An effective apprenticeship program should be influenced and directed by local union politics.

True

An induced voltage is always opposite in polarity to the applied voltage.

43.3 kva

An open transformer bank supplies 3-phase power on a 3-wire service line. The transformers are each rated at 25 kVA. The power rating of this bank is ? .

86.6 %

An open wye-open delta bank with equally sized transformers has a kVA rating of ? of the combined transformer power ratings.

False

An open wye-open delta transformer bank will operate with a floating or grounded primary neutral bus.

Best

Apprentices selected by the AJATC are the ? of those who have applied.

66%

Approximately what percentage of the apprenticeship indenture requirements have been completed by the start of the third year?

AJATC

As a supervisor, one will be required to evaluate the performance of the apprentice and report findings to the ? .

Increases

As the circuit current increases, the magnetic field that it creates ? .

True

At higher distribution circuit voltages, the risk to line crews increases.

75%

Bank capacity is ? of total nameplate capacity in an open wye-open wye bank.

on-the-job training instructor

Before becoming a classroom instructor, one should have first served as a(n) ? .

Capacitors

By conducting load studies and properly sizing and placing ? , an electrical provider can reduce the kilovolt-amperes that have to be delivered to a customer.

The same load can be supplied at 4 times the distance

By doubling the voltage of a line, ? .

True

By placing the secondary 120/240-volt coils in parallel, the full kVA of the transformer is available at 120 volts.

False

Calculating load checks on an open delta bank is the same as calculating load checks on a closed delta bank.

Farads (F)

Capacitance is measured in ? .

Ohms

Capacitive reactance is measured in ? .

False

Capacitive reactance is the opposition to the flow of current in an AC circuit due to the presence of inductive reactance.

Inductive reactance

Capacitor installation will offset a circuit's ? and reduce the I2R line loss.

Aluminum

Capacitor plates are constructed from two long sheets of ? .

False

Capacitors are constructed to allow current to flow through them.

True

Capacitors are devices that oppose a change of voltage.

Shunt

Capacitors installed on distribution circuits are often referred to as ? capacitors.

5 time constants

Charging or discharging a capacitor takes ? .

False

Closed transformer banks that deliver 240-volt, 3-phase and 120/240-volt, single-phase power operate with fewer losses than open banks that supply similar loads.

73%

Converting a distribution system from delta to wye increases the capacity of the system by ? .

True

Current and voltage checks are an integral part of analyzing circuit problems.

95 %

Customers with inductive loads and a power factor of less than ? are normally charged a penalty fee.

False

Customers with motors that have a low power factor are a desirable load for an electrical provider.

Decrease

Decreasing the amount of inductance in a circuit will cause inductive reactance to ? .

Set up on insulators

Distribution capacitor banks in a substation are normally surrounded by a fence with danger signs and are ? .

True

Distribution capacitors work by improving the power factor from the installation point back to the source.

True

Doubling the voltage on a line reduces the current required to supply an equal amount of power by 50%.

True

Electro-magnetic induction is the process of inducing a voltage in a conductor by the action of a magnetic field.

An electrostatic field

Energy is stored in ? in a capacitor.

False

Higher voltage distribution circuits with longer reach have greater reliability.

A smaller

If 20 volts AC were connected to a coil, it would result in ? current than 20 volts DC connected to the same coil.

240 degrees

If B phase is lagging A phase by 120°, C phase will lag A phase by ? .

True

If a CSP transformer is used in a closed wye-delta transformer bank as the lighter, there is a risk of an open neutral condition on the single-phase, 120/240-volt circuit if the secondary circuit breaker is opened or trips.

Capacitor

If a circuit is balanced, all of the energy released by the inductor is absorbed by the ? .

58%

If a faulted transformer is cleared and the remaining two transformers are connected as an open wye-open delta, the bank only has ? of the capacity of the original bank.

50%

If a faulted transformer is cleared and the remaining two transformers are connected open wye-open wye, the bank has ? of the capacity of the original bank.

Transformer would burn up

If a transformer rated at 240 volts AC was connected to a 240-volt DC source, the ? .

BC

If a typical single-phase transformer with three secondary terminals delivers 120/240 volts to a residential customer, the internal ? coil leads are connected to the X2 terminal.

Voltage could rise to an intolerable level

If during periods of light loading, excessive amounts of capacitive reactance is added to a circuit, the ? .

Surface area of the plates

If the ? of a capacitor is increased, the strength of the capacitor will be greater.

Inductance of the coil will decrease

If the number of turns of wire in a coil is decreased, the ? .

Tank will be energized at primary potential

If the only tank ground on a single bushing transformer becomes broken, the transformer ? .

4160/7200Y V

If transformer primary windings are delta banked on a 4.16-kilovolt, 4-wire primary circuit, the primary nameplate voltage rating must be ? .

43.5 kva

If two 25-kVA transformers are connected into an open wye-open delta bank, the total bank capacity would be ? .

Ohms

Impedance is measured in ? .

neutral

In a 120/240-volt residential service, the ? carries the current difference of the two legs.

Polarity

In a 120/240-volt service, one 120-volt leg is opposite in ? to the other.

False

In a 3-phase system, the three voltages are of different magnitudes.

Lags behind the voltage

In a distribution circuit with a large inductive reactive component, the current ? .

1.73

In a secondary connected delta, winding current multiplied by ? is equal to line current.

True

In a vector line drawing of a wye bank, if the head of a vector line comes in contact with the tail of another vector line, it will be a dead short.

False

In a wye banked secondary circuit, the star point leads from the X bushings of the outboard transformers carry only the load imbalance and may be of reduced size.

Voltage is rising

In an AC circuit, current flows into a capacitor only when the ? .

137.2 KVA

In an open wye-open delta bank, the delta winding reads 286 amperes. The bank is providing service at 480 volts. The kVA loading each transformer is ? .

XL

In formulas, the symbol used for inductive reactance is ? .

False

In order to parallel the coils on a transformer with four secondary bushings, it is necessary to remove the lid.

True

Increasing the frequency will cause inductive reactance to increase.

Voltage drop

Inductance in distribution circuits contributes to ? in the line.

Henries (H)

Inductance is measured in ? .

Ability of a magnetic field to induce a voltage on a conductor

Inductance is the ? .

Voltage

Inductance is the ability of a current-carrying conductor, coil, or circuit to induce a ? into itself or adjacent circuits.

Ohms

Inductive reactance is measured in ? .

False

It is not possible to connect a transformer with two high-voltage terminals phase-to-phase on a wye system.

True

Multiple rolls (plates) inside a capacitor can be interconnected in series or parallel.

90 %

Of all transformers installed in North America, ? are installed as single-phase transformers to supply a 120/240-volt service.

85%

Of those who start and are indentured into the IBEW/NECA apprenticeship, ? will go on to satisfactorily complete their apprenticeships.

KVAR

On nameplates, the unit of measure for capacitor power is the ? .

Lower

On transmission lines, the closer the lines are spaced, the ? the effect of inductance.

False

On wye systems, unlike transformer bushings are joined with jumpers, and lines are connected at points where the bushing leads are connected.

True

On-the-job training is one important factor that contributes to the high IBEW/NECA apprenticeship completion rate.

age

One factor the apprenticeship committee considers about an applicant prior to selection into the apprenticeship program is ? .

6

One procedure to find a bad transformer in a 3-phase bank is to isolate and test each individual transformer. This involves ? steps.

Contractor

One should seek advice and study the business side of the industry before deciding to become a(n) ? .

False

Only transformers with two insulated high-voltage terminals can be installed on wye systems with a grounded neutral.

True

Only transformers with two primary bushings can be installed on a primary delta system.

True

Only transformers with two primary bushings can be used to supply 3-phase power when the primary circuit is delta connected.

Voltage fluctuations

Overloaded transformer banks can cause ? to/for the customer.

False

Power factor correction is not one of the main functions of a capacitor. Power factor is corrected by the substation transformer.

apparent power

Power factor is equal to real power divided by ? .

As a percent

Power factor is normally expressed ? .

True

Reactive power required by inductive loads increases the amount of kilovolt-amperes a supplier must provide.

True

Single-phase motors produce vibrations caused by a pulsing torque pattern.

False

Single-phase, two-bushing shunt capacitors are most often banked together in a grounded delta configuration.

On the job

The "how" of the trade is learned ? .

26 kva

The 3-phase power feeding a small pump motor is powered by two transformers banked in an open-delta. Each transformer has a 15-kVA rating. The capacity of the bank is ? .

True

The Code of Federal Regulations pertaining to the disconnecting and shorting of capacitor banks is found in 1910.269.

Capacitance

The ability of a circuit or a component to store an electrical charge is called ? .

False

The accepted method used to de-energize a large fixed capacitor bank by opening cutouts is to quickly pull the gates between cycles.

Farad

The basic unit of capacitance is the ? .

False

The best way to calculate total bank load on a delta bank is to calculate individual transformer loads and add them together.

why

The classroom-related instruction is designed to teach the " ? " of the trade.

Star point

The common connection point on a 3-phase wye connected bank is also called the ? .

3 wire delta

The earliest poly-phase systems adopted by the electrical industry in the United States is the ? system.

False

The farther apart the plates of a capacitor are, the more capacitance there is.

True

The faster the frequency of a circuit, the faster a capacitor charges and discharges.

Per phase

The formula (kVA × 1,000) ÷ (line-to-line voltage × 1.73) is used to calculate the full load current ? .

I x E divided by 1000

The formula to calculate an individual transformer load in kVA is ? .

XL = 2πfL

The formula used to calculate inductive reactance is ? .

True

The grounded primary neutral of an open wye-open delta transformer bank carries full primary current.

secondary coils are in series

The higher voltage rating of a single-phase transformer's secondary windings is achieved when the ? .

120 degrees

The individual sine waves of a 3-phase system are ? out of step with each other.

Counter or back EMF

The induced voltage in a coil is in a direction so as to oppose the original voltage and is known as a ? .

180 degrees

The induced voltage of a coil is ? out of phase with the applied voltage.

True

The induced voltage of an inductor can limit the flow of current through the circuit in a manner similar to resistance.

Increase

The inductance of a coil will ? if the turns of wire in the coil are wound closer together.

Oiled paper

The insulation used in a typical distribution capacitor is usually ? or polyethylene film.

Local union business manager

The job steward is appointed by the ? .

L

The letter ? is used as a symbol to designate inductance.

1.73 times greater than

The line-to-line voltage in a wye system is ? the voltage across the transformer windings of a wye connected bank.

19920 v

The line-to-neutral voltage on a 34.5-kilovolt wye system is ? .

12.5 kv wye

The most commonly used distribution system in the country is the ? .

False

The only way to supply 240 volts, phase-to-phase to streetlights is to use a 240/480-volt transformer and tap X1 and X2.

Reactance

The opposition to current flow in an AC circuit consists of resistance and ? .

Inductive Reactance

The opposition to the flow of alternating current in an inductor is called ? .

Inductive Reactance

The opposition to the flow of current in an AC circuit due to the presence of inductance is called ? .

Dividing KW by KVA

The power factor of a circuit is found by ? .

15 kva

The power lost by the conductors when delivering electricity to an end line customer on a certain 4.16-kilovolt distribution line is 60 kVA. If the line was to be converted to 8.32 kilovolts and an equal amount of power is being delivered, the line loss would be ? .

True

The primary and secondary vector lines of an individual transformer are always at the same angle and point in the same direction.

Phase to phase

The primary winding of a single-phase transformer connected in delta on a 2,400-volt system would be connected ? .

Apparent power

The product of the total voltage and the total current in an AC circuit is called ?

Power Factor

The ratio of true power (expressed in watts) to apparent power (expressed in volt-amperes) is called ? .

heads to tails

The secondary vector lines of a wye-delta phasor drawing are connected ? .

False

The secondary windings of a transformer with voltage ratings of 120/240 volts must be connected in series to supply 208-volt, 3-phase power on a 4-wire service line.

line to line/ 2400

The secondary windings of three substation transformers are banked in a delta. The potential across the windings is 2,400 volts. The output voltage from ? is ? .

C

The symbol for capacitance is ? .

Xc

The symbol for capacitive reactance is ? .

Z

The symbol for impedance is ? .

L

The symbol for inductance is ? .

XL

The symbol for inductive reactance is ? .

X

The symbol for reactance is ? .

True

The term phasor is the proper name for a vector when used in electrical drawings.

Time constants

The time it takes to charge and discharge a capacitor is measured in ? .

Impedance

The total opposition to the flow of current in an AC circuit is called ? .

kW / KVAR

The total or apparent power required by an inductive device is a composite of ? and ? .

Ohm

The unit of measurement for inductive reactance is the ? .

equal to the voltage from line to line

The voltage across a transformer winding in a delta system is ? .

58 %

The voltage across a wye connected transformer coil is ? of the line-to-line voltage on the wye system.

Dielectric

The voltage rating of a capacitor is actually the rating of the ? .

271 A

Three 37.5-kVA transformers connected as a 3-phase bank have a full load capacity rating of ? at 240 volts. (Round the FINAL answer to the nearest half.)

X2 and X3

To connect the secondary coils for series operation on a transformer with four secondary terminals, the ? terminals are joined with an external jumper.

AC and BD

To parallel the secondary windings of transformers with three secondary terminals, the ? coil leads are paired and connected to the terminal studs inside the tank.

Fused cutout

To protect a distribution system from an internally shorted capacitor, a ? is used to clear the faulted unit from the circuit.

347 V/Y

To provide a 347/600-volt, 3-phase service, transformers with a secondary voltage rating of ? must be ? banked.

True

To successfully compete in the marketplace, the electrical industry needs all of its workers to be highly productive and efficient.

277 V

To supply 480-volt, 3-phase power with the transformer secondary coils banked in a wye configuration, the transformer secondary voltage ratings must be ? .

7200/12470Y V

Transformers installed on a 12.5-kilovolt, 4-wire circuit must have a nameplate primary voltage rating of ? when the primary is banked in a wye.

2400 volts

Transformers installed on a 4.16-kilovolt, 4-wire wye system can have primary voltage ratings of 4,160 volts or ? .

False

Transformers with primary windings in a delta configurations can only be connected to delta 3-wire primary circuits.

True

Transformers with secondary coil ratings of 120/240 volts can supply a 240/416-volt service with the secondary coils connected in series and banked in a wye configuration.

Parallel and wye

Transformers with secondary voltage ratings of 120/240 volts are banked to supply 3-phase 208-volt power on a 4-wire service line. The secondary coils must be connected in ? banks.

parallel/ wye

Transformers with secondary voltage ratings of 120/240 volts can be used to supply a 120/208-volt load when the secondary coils are connected in ? and ? banked.

True

Transformers with single primary bushings may be installed on wye systems.

True

Transformers with single primary bushings may be used to construct wye-wye banks.

100 kva

Transformers with two secondary windings and power ratings greater than ? have four secondary bushings.

True

True power in a DC circuit containing only resistance is the product of total voltage and the total current.

Watts (W)

True power is measured in ? .

True

Two delta-wye transformer banks can be paralleled if voltages and angular displacements are the same.

The distance of the service drop

Two factors that might account for low voltage at a customer's meter are bad connectors and ? .

False

Two lines that have the same rotation will always phase together.

True

Two transformers rated 120/240 volts on the secondary can be connected to serve a single-phase, 480-volt load.

34.6 A

Under a balanced load condition, the primary transformer coils of a closed delta bank each draw 20 amperes. The current through each of the primary leads is ? .

True

Vector lines are joined from head to tail in delta systems.

90 degrees

Voltage across a capacitor lags the current through the circuit by ? .

63.2 percent

When a capacitor charges and discharges during each time constant, the voltage will change by ? of the amount left to reach the fully-charged state.

Low

When a circuit has a large portion of its impedance made up of inductive reactance, it will have a ? power factor and a lagging current.

False

When a circuit is made up of resistance alone, it will have a high power factor and the current will be out of phase with the voltage.

False

When a conductor is wound into a coil and placed on an iron core, the inductance is greatly decreased.

Primary coil

When a transformer is connected to an AC source, the current is limited by the inductance of the ? .

True

When checking a 3-phase bank, the problem may be that someone installed primary side fuses that are too small.

8320 V

When converting a 4,800-volt, 3-wire delta system to a 4-wire wye system, the line-to-line voltage is ? .

300 A

When current through the secondary windings of a wye connected transformer bank is 300 amperes, the current through the load lines will be ? .

5 minutes

When energizing a capacitor, if proper contact is not made the first time with the cutout, wait ? before trying again.

Changing the fastest

When looking at the current charging a capacitor and the voltage across the capacitor, the current is at a maximum when the voltage is ? .

False

When the 120/240-volt secondary windings of a transformer are connected for series operation, the secondary vectors are connected head to head or tail to tail.

Polarity

When the current changes direction, the magnetic field it creates changes ? .

False

When troubleshooting a transformer bank, the transformer that does not produce secondary voltage is always the bad one and needs replacing.

240 v

Which one of the following 3-phase service types requires a delta secondary configuration?

The Journeyman

Who is the person most responsible for the success of a Journeyman?

False

Wye-delta transformer banks can be connected with either 30° or 120° angular displacements.

180 degrees

Wye-wye and delta-delta transformer banks can have either a 0° or ? angular displacement.