In an ideal transformer, the primary-to-secondary voltage ratio is equal to which quantity?
Transformers
Question · Easy
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Short
A single-phase transformer has 2,400 primary turns and 240 secondary turns. With 2,400 V on the primary, the secondary voltage is approximately:
For an ideal transformer with turns ratio Np:Ns = 4:1 and primary current of 25 A, secondary current is approximately:
Question · Medium
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What is the primary purpose of a power transformer on a utility distribution system?
Nameplate kVA on a three-phase power transformer rates the unit based on:
Percent impedance (%Z) on a transformer nameplate is most useful for estimating:
Question · Hard
When paralleling two power transformers on the same bus, a critical matching requirement is that they have:
A delta-wye distribution transformer bank is commonly used because it can:
Instrument current transformers (CTs) are primarily used to:
Before working on a CT secondary circuit that is still energized on the primary, workers must:
ONAN cooling class on an oil-filled transformer means cooling is primarily by:
A load tap changer (LTC) on a power transformer is used mainly to:
Ohm’s law states that voltage equals:
Electrical Knowledge
In a pure resistive AC circuit, power factor is:
Three-phase real power for a balanced system is calculated as:
On a balanced wye system, line-to-line voltage relates to line-to-neutral voltage by:
Apparent power is measured in:
In the United States, utility alternating-current systems normally operate at a nominal frequency of:
A circuit draws 40 A at 480 V three-phase with a power factor of 0.85. Approximate real power is:
Inductive loads such as motors typically cause current to:
Skin effect in AC conductors means that:
A short-circuit fault on a power system produces high current mainly limited by:
Voltage drop on a feeder increases when:
A 480 V three-phase motor nameplate lists FLA of 60 A. At full load with PF 0.90, approximate input real power is:
ACSR conductor consists of:
Conductors
Ampacity of a conductor is best defined as:
Compared with copper of the same cross-sectional area, aluminum conductors generally:
Bundled conductors on high-voltage transmission lines are used primarily to:
Conductor sag on an overhead span increases when:
AAC as a conductor designation typically means:
Compression connectors for overhead aluminum conductors should be installed with:
Messenger wire on an aerial cable assembly primarily provides:
XLPE insulation on medium-voltage power cable stands for:
A concentric neutral on URD cable typically serves as:
Derating conductor ampacity is often required when:
The purpose of a conductor shield (semiconducting layer) in medium-voltage cable is to:
When selecting overhead conductor size, designers must consider ampacity plus:
Parallel conductors of the same phase must be installed so that:
A jumper on a power line is best described as:
Annealed soft copper is preferred for some connectors and grounding because it is:
Overhead supply lines are primarily designed and regulated for safety clearances under which widely used code for electric supply stations and lines?
Overhead Lines
Vertical clearance of overhead conductors above ground must be evaluated at:
For roads subject to truck traffic, NESC Table 232-1 requires on the order of 15.5 ft minimum vertical clearance for which common category?
A shield wire (static wire) on a transmission line is installed mainly to:
Suspension insulator strings on high-voltage lines primarily:
On joint-use poles, communication facilities are generally placed:
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