Lesson 1 quiz 1 Lesson 3 q 1-15 lesson 4 20-32 lesson 5 10-25
A ? is a power supply consisting of two phases that are 90° out-of-phase. Select one: a. 2-phase system b. double-delta connection c. Scott connection d. Scott system
2 Phase sytem
A dielectric absorption test must be corrected to ? . Select one: a. 20°C b. 30°C c. 40°C d. 50°C
40°C
In North America, virtually all power systems now operate at ? . Select one: a. 25 Hz b. 50 Hz c. 60 Hz d. 120 Hz
60
What is the full load secondary current of a 3-phase 75-kilovolt-ampere dry-type transformer at 600 volts?
72.16
An open delta maintains a balanced phase relation better than a T-connection. Select one: True False
False
Rubber insulating gloves must be laboratory tested by an approved laboratory once every 12 months. Select one: True False
False
Only special order two-winding transformers have high-voltage leads and low-voltage leads connected to the windings. Select one: True False
False All 2 windings have this
An autotransformer does not have any part of the windings shared by the primary and secondary. Select one: True False
False Auto transformers are connected
A high polarization index may indicate wet or damaged insulation. Select one: True False
False a low polarization index
A closed delta configuration can be used when selecting a transformer to allow for future expansion. Select one: True False
False it's open delta
Which of the following is not a system requirement for satisfactorily connecting two or more transformers in parallel? Select one: a. Having a synchronous converter b. Having the same angular phase displacement and phase sequence c. Having the same percent of impedance d. Having the same polarity e. Having the same voltage ratio
Having a synchronous converter
Which of the following transformers can be used as a direct replacement for a 25-hertz transformer?I. A single 60-Hz transformer that has a voltage rating of more than twice the rating of a 25-Hz transformerII. Two transformers with a current rating matching the 25-Hz transformer can be connected in seriesIII. Two transformers with a voltage rating matching the 25-Hz transformer can be connected in parallelIV. Two transformers with a voltage rating matching the 25-Hz transformer can be connected in series
I. A single 60-Hz transformer that has a voltage rating of more than IV. Two transformers with a voltage rating matching the 25-Hz transformer can be connected in series
Which of the following are aspects of a transformer that should be checked when performing an internal inspection?I. Buildup of dust or other contaminantsII. Coil damageIII. DamageIV. Loose laminationsV. Loose nuts and boltsVI. Position of coils Select one: a. I., II., and III. only b. I., III., and VI. only c. II., III., and IV. only d. I., II., III., IV., V., and VI.
I. Buildup of dust or other contaminantsII. Coil damageIII. DamageIV. Loose laminationsV. Loose nuts and boltsVI. Position of coils
A GFCI protects against ground faults and line-to-line contact hazards. Select one: True False
True
A synchronous converter is a rotating machine that produces a DC current from an AC source or AC current from a DC source. Select one: True False
True
A two-winding transformer is the most common type of transformer. Select one: True False
True
All terminals must be treated as if there may be a potential shock hazard when working on a transformer. Select one: True False
True
Anyone performing a test on a transformer must stand clear of all parts of the circuits. Select one: True False
True
Before working on a transformer, the primary and secondary must be locked out. Select one: True False
True
Dry-type transformers are cooled by circulating air. Select one: True False
True
Liquids that are flammable but have a relatively high fire point have been developed for use in transformers. These are less-flammable liquids. Nonflammable-liquid transformers are filled with a liquid that has no flash point or fire point and does not burn in air. Select one: True False
True
Lockout is the process of removing the source of electrical power and installing a lock that prevents the power from being turned on. Select one: True False
True
When selecting a transformer, a two-winding transformer can be interconnected for use as an autotransformer by connecting the primary in series with the secondary. Select one: True False
True
When working on a transformer, a worker should always disconnect test leads from the transformer before disconnecting the leads from the test set. Select one: True False
True
When working on a transformer, a worker should ensure that the ground connection is the first made and the last removed. Select one: True False
True
When working on a transformer, a worker should follow all NFPA 70E and OSHA requirements. Select one: True False
True
A 60-hertz transformer can be used as a direct replacement for a 25-hertz transformer. Select one: True False
f
A ? is a connection at the service equipment that connects the equipment grounding conductor, the grounding electrode conductor, and the grounded conductor. Select one: a. ground fault circuit interrupter b. lockout c. main bonding jumper d. separately derived system
main bonding jumper
Some synchronous converters operate on 6-phase power. Select one: True False
t
For transformers rated at 600 volts, nominal, or less, with primary currents of 9 amps or more, one option is to protect the primary winding at ? of the rated primary current. Select one: a. 125% b. 150% c. 250% d. 300%
125%
What is the full load primary current of a 3-phase 15-kilovolt-ampere dry-type transformer at 480 volts?
18
? current flows into insulation to charge the insulation like the plates of a capacitor. Select one: a. Capacitive absorption b. Capacitive leakage c. Conductive leakage d. Polarization absorption
Capacitive leakage
An ? is a shock that results anytime a body becomes part of an electrical circuit a. arc blast b. arc flash c. electrical shock d. voltage spike
Electrical Shock
Once its fuse has blown, a transformer primary can be considered de-energized. Select one: True False
F
If rubber insulating gloves or leather protectors are found to be defective, they must be discarded and/or destroyed in the field. Select one: True False
F They are given to the supervisor
A hipot tester uses a very low voltage for testing. Select one: True False
False
A two-winding transformer is a transformer with an electrical connection between the primary and the secondary. Select one: True False
False
A winding insulation test should be conducted with a digital multimeter. Select one: True False
False
? is the ratio of the power dissipated in the insulation in watts, to the apparent power in volt-amperes. Select one: a. Dielectric index b. Insulation power factor c. Polarization index d. Turns ratio
Insulation power factor
A(n) ? is a method of wiring transformers where two separate windings are interconnected on each phase in a zigzag fashion. Select one: a. 3-wire, 2-phase connection b. double-delta connection c. interconnected wye connection d. Scott connection
Interconnected wye
Ear protection devices are assigned a ? rating number based on the noise level reduced. Select one: a. decibel protection b. noise reduction c. sound reduction d. volume protection
Noise reduction
A ? is two or more transformers wired in parallel that carry a common load. Select one: a. double-delta connection b. parallel connection c. Scott connection d. T-connection
Parallel
? current is caused by the polarization of molecules within the dielectric material. Select one: a. Capacitive absorption b. Capacitive leakage c. Conductive leakage d. Polarization absorption
Polarization absorption
? are protective devices that take a transformer off-line in the event of a fault.
Relays
? is a floor covering that provides technicians protection from electrical shock when working on live electrical circuits. Select one: a. Floor shielding b. Plastic electrical insulation c. Rubber insulating matting d. Spray-coated flooring
Rubber insulating matting
A(n) ? is a method of wiring two transformers to transform from 3-phase to 2-phase or 2-phase to 3-phase. Select one: a. interconnected wye connection b. parallel transformer connection c. Scott connection d. T-connection
Scott connection
A(n) ? is a low-cost method of wiring two transformers to provide 3-phase power. Select one: a. double-delta connection b. interconnected wye connection c. Scott connection d. T-connection
T connection
A 4-wire, 2-phase system has no connection between the coils. Select one: True False
Tue
Which of the following is not a common type of relay used to protect transformers? Select one: a. Differential relay b. Overcurrent relay c. Overvoltage relay d. Undercurrent relay e. Undervoltage relay
Undercurrent relay 1. Differential relays are used to detect unexpected differences between the primary and secondary currents.2. Overcurrent relays are used to detect unexpectedly high phase currents.3. Overvoltage and undervoltage relays are used to detect unexpectedly high or low voltages. The correct answer is: Undercurrent relay
When two or more conductors are near each other, charge builds up in the insulation between the wires and acts as a ? . Select one: a. capacitor b. conductor c. resistor d. shield
a capacitor
A(n) ? is a short circuit through air. Select one: a. arc blast b. arc flash c. voltage spike d. voltage surge
arc flash
