2-2
A transformer is rated at 7,200/12,470-120/240. If you parallel the secondary coils AC,BD, full amperage capacity is available at A. 120 v B. 208 v C 220 v D 480 v
A 120v
If load test was done on a transformer, and the load on A-conductor was the same as the load on B-conductor, the condition would be referred to as. A. A balanced load B. Having a perfect power factor (100%) C. In phase D. Load neutral
A a balanced load
The voltage level that can flashover the outside of equipment, such as an insulator, is called the _______ Level A. Basic impulse B. Flashover arcing C. Overload insulation D. Skin effect
A basic impulse
A _____ Reduces the risk of violent transformer failure when it is in series with the cutout A. Current limiting fuse B. Current shunt fuse C. Solidly connected ground D. Voltage limiting fuse
A current limiting fuse
To vector a 3-phase system, it is essential to establish a _______ Of the phases A. Fixed reference B. Sequential order C. Sine wave D. vector
A fixed reference
Kilovolt-ampere (KVA) rating of a transformer represents A. Full load output B. Total impulse/insulation of the level of the secondary coils C. Total transformer impedance D. Total voltage input
A full load output
Lockout/tagout is normally removed by the ________ other than in an emergency situation A person who installed it B project or job supervisor C project or safety director D system operator
A person who installed it
if two transformers are connected in parallel and a primary fuse blows on one of the transformers, the other transformer will A. Back-feed the one with the blown fuse B. Operate at 50% of full load C. Operate normally D. Overload and overheat with the burden of the other transformer
A. Back-feed the one with the blown fuse
While inspecting a transformer prior to installation, if there is a slash (/) between the primary voltages, the transformer should have _______ Primary bushings and is suitable for a delta primary connection. A. 1 B. 2 C. 3 D. 4
B 2
A spot load check on a transformer finds; A lead with 110 volts and 105 amperes, B leads with 114 volts and 95 amperes. What is the exact KVA being taken off the transformer_ A. 22KVA B. 22.38KVA C. 25.5KVA D. 27.7KVA
B 22.38 kVa
A transformer that is energized, but under no load, can draw as much as current taken in by a loaded transformer of the same size. A. 3% B. 5% C. 10% D. 12%
B 5%
An isolation link or current limiting fuse, in an underground transformer is A. Another name for the replaceable fuse B. Between the replaceable fuse and the primary coil C. Easily replaced in the field D. Not provided on most underground transformers
B Between the replaceable fuse and the primary coil
One problem with small 3-phase voltage unbalance is that they cause. A. Excessive voltage to ground on the grounded conductor B. High current unbalance C. High resistance on the conductor with the large voltage drop D. Over voltage at the customer's meter
B High current unbalance
When using test instruments, the main reason for the increase in the use of digital electronic technology is? A far greater accuracy B greater measuring capability C safety D size and transportability
B greater measuring capability
When paralleling two transformers, the ______ Of the two transformers must be within 107.5% to 92.5% of each other A. Current capacity B. Impedance C. Power factor D. voltage
B impedence
As the temperature drops below 30 degree C, a transformer KVA rating. A. Decreases by 1.5% for each degree B. Increase by 1% for each degree C. Increase by 2% for each degree D. Stays the same since the KVA is fixed
B increase by 1% for each degree
The H2 terminal on a single bushing transformer is solidly connected to the A. H1 and H2 winding B. Inside of the tank C. X1 terminal D. X2 terminal
B inside of the tank
One requirement of the 1996 migratory bird treaty act regarding new transformer installation to protect birds from electrocution is to A. Ground all conducting parts B. Install bushing covers C. Install cross arm covers D. Use only fiberglass insulator pins
B install bushing covers
Polarity tests should be performed on a transformer with a missing or damaged nameplate and the polarity. A. Identified with a plastic tag around the primary bushing B. Marked with a with dot near H1 and X1 on the transformer case C. Noted on the job specifications or as-built drawings 'D. Running in the default clockwise direction
B marked with a dot near H1 and X1 on the transformer case
When working on a CSP transformer, it is highly recommended that before work is performed on a de-energized secondary,_ A. All conditions (both primary and secondary) be disconnected B. The primary lead taken off the line C. The red warning light has been turned off D. The secondary conductors have been grounded
B the primary lead taken off the line
The secondary amperage available on a 25 KVA transformer at 120 volts is ? A. 77 A B. 104 A C. 208 A D. 312A
C 208 A
The strength of an electromagnetic field in a transformer is dependent on the case of which the core is magnetized, the amount of the current following, and the A. Amount of resistance in the core B. Construction material ( the more conductive is desirable) used to build the frame and internal supports of the transformer C. Number of turns in the winding D. Secondary current demand
C Number of turns in the winding
The most common use of a dual-voltage transformer is A. To bring a customer back online while troubleshooting a problem B. When a primary supply voltage is unstable from large equipment use on the circuit C. When a utility has two different distribution voltages D. When the customer needs two separate voltages supplied to the service
C When a utility has two different distribution voltages
If you have installed several 120 volt security lights and need the total capacity of the transformer, you should A. Connect all the lights between X1, X2 .B. Connect half of the lights between X1, X2 and half between X1,3 C. Connect the coils in parallel D. Leave the coils in series and install a larger KVA transformer
C connect the coils in parallel
A typical distribution transformer consists of a(n) A. Armature B. Capacitor. C. Core and coil assembly D. Electric cooling fan
C core and coil assembly
Industry standards for electrical transformers call for the H1 terminal to be located on the A. Backside when facing the front of the transformer B. Left side when facing the primary C. Left side when facing the secondary D. Right side when facing the secondary
C left side when facing the secondary
When performing a polarity test on a single-phase transformer, the voltmeter reading on a subtractive transformer will be _______ The source voltage. A. Higher than B. The same as C. Lower than D. Lower by one-half
C lower than
A test instrument that is used to test for insulation breakdown is the A. Circuit analyzer B. Continuity tester C. Megohmmeter D. Voltage indicator
C megohmmeter
A transformer changes the voltage and current from one level to another because of the A. Current ratio B. Customer's service demand C. Number of turns in each coil D. Supply voltage
C number of turns in each coil
Graphical illustrations using vectors can easily show the following transformer qualities, transformer output voltage have magnitude, direction, phase sequence, and. A. Current flow B. Impedance C. Phase angle D. Voltage peaks
C phase angle
Primary voltages can be determined by multiplying transformer turns ratio by the A. Nominal primary voltage, single-phase B. One-half secondary voltage C. Secondary output voltage D. Secondary voltage at the right hand bushing
C secondary voltage
A voltage indicator may not detect the presence of voltage in a wire that is. A. GFCI protected B. Insulated C. Shielded D. wet/ moisture present
C shielded
Kilovolt-ampere being drawn off a transformer can be found by multiplying secondary voltage times secondary amperage and then dividing by. A. 0.707 B. 1.73 C. 100 D. 1,000
D 1000
The transformer ratio is 10:1 the secondary voltage is 120 volts, and the primary voltage is A. 12v B. 120v C. 240v D. 1,200v
D 1200v
The initials CSP on a transformer mean ? A. Closed secondary-primary B. Closed secondary protection C. Completely secured primary D. Completely self-protected
D Completely self-protected
The most common dual-voltage distribution transformer is rated at A. 4,160x7,200-120/240 ? B. 7,200×14,400-277/480 C. 7,630×13,200-240/480 D. 14,400×7,200-120/240
D D. 14,400×7,200-120/240
The purpose of forming a loop in the transformer lead and inserting the lead into the top of the terminal is the A. Copper leads conduct better when they are looped B. Leads are easier to work on when troubleshooting C. Looping creates greater clearance from the tank to make connections D. Looping prevents water from getting into the connection
D Looping prevents water from getting into the connection
If a transformer is equipped with a tap changer, it must never be. A. Banked together with another transformer B. Changed by hand C. Changed one tap at a time D. Operated while the transformer is energized
D Operated while the transformer is energized
The four internal parts of a distribution transformer are primary windings, secondary windings, iron core, and A. Bushings B. Cooling fan C. Inspection plate D. insulation
D insulation
The length of a vector line is proportional to the A. Capacitance B. Impedance C. Inductance D. magnitude
D magnitude
The electrical worker installing the transformer should check the tap changer position before it is put into service. Unless otherwise instructed, the tap setting must always be placed A. At the highest tap setting B. At the lowest tap setting C. In the open position D. On full winding (100%)
D on full winding (100%)
If you hold a CSP's handle in the "C" position on a permanent fault, the secondary breaker will A. Close B. Not carry the added current C. Pick-up within one minute D. reopen
D reopen
The main reason meter fuses blow (when the meter has fuses) is A. Faulty test leads B. Over current C. Setting the function D. Setting the function and selector switches to an improper function position
D setting the function and selector switches to an improper function postition
Medium and large-large transformers use _______ Type wire for a more compact and solidly built coil, which also provides better conductivity for the heat to flow out of the windings. A. Aluminum B.Compacted round copper C. Segmental copper D. Square and rectangle
D square and rectangle
A transformer equipped with taps changes the ? Of the secondary output. A. current B. Impedance C. Primary lug attachment D. Turns ratio
D turns ratio
The electrical worker who is familiar with the vector 30 degree increments ______ Can plot any 3-Phase system in A. 3-phase bank chart B. Line chart C. Phase angle graph D. wheel
D wheel
To determine the power being drawn a transformer, use a multi-meter to find the voltage across and the current through the secondary coils, with these values and the formula, KVA= ______ A spot check of transformer power will be found. A. Exl/1,000 B. W/ExI C. WxixPF/100 D. KWxPF/ 1,000
D. KWxPF/ 1,000
You can get 480 volts out of two 120/240-volts transformers by A. Paralleling the primary and connecting the series B. Paralleling the secondary and putting the primary in series C. Removing the grounding straps, paralleling the primary, and connecting the secondary D. Removing the grounding straps, connecting the secondary in series, and paralleling the primary side
D. Removing the grounding straps, connecting the secondary in series, and paralleling the primary side
Clip-on ammeter tests should be taken during. A. Normal daytime hours to get a true reading on load demand B. The nighttime hours when the power usage is at the most constant demand C. The summer months when the load is most demanding D. The time of day when the load is considered at the highest peak
D. The time of day when the load is considered at the highest peak
With a CSP transformer, the primary fuse link. ? A. Does not protect against internal faults B. Is designed to protect on external overloads C. Will detect any small overload before it gets to the primary winding D. Will not de-energize the primary lead from the transformer to the line
D. Will not de-energize the primary lead from the transformer to the line
