Transformers

If a transformer steps voltage down what happens to the current?

Current is then stepped up.

Where would you find 120V in a Delta - Delta 120V /240V transformer? Where is the 240V?

120V is between the center-tapped terminal and each ungrounded terminal and 240V across the full windings of each phase.

In an AC circuit how many horses are always working at varying lengths?

3 forces inductance capacitance and true power

What two leads connected increase secondary voltage by 5%? What two leads connected decreases secondary voltage by 5%?

7-2 increases by 5% and 5-4 decreases by 5%.

What does a power factor of less than one represent?

A lagging current for motors and inductive devices

What happens if the inductive load of a motor is completely balanced by a capacitor?

A maximum power of unity results and all input energy services to perform useful to work,

Transformer

A static device consisting of one or more windings with a magnetic core. Transformers are used for introducing mutual coupling by induction between circuits.

Power transformer

A transformer that is designed to transfere electrical power from the primary circuit to the secondary circuit to step up the secondary voltage at less current or step down the secondary voltage at more current, with the voltage-current product being constant for either the primary or secondary.

Autotransformer

Any transformer in which primary and secondary connections are made to a single winding. The application of an auto transformer is a good choice where a 480Y /277V or 208Y/120 V, 3 phase, 4-wire distribution system is used

The main purpose of a transformer is to ______________ .

Change the output voltage

Which transformer system provides three-phase power while allowing lightning to be connected between any of the secondary phases and the neutral?

Delta-Wye Transformer

Rectifiers

Devices used to change alternating current to direct current.

What type of transformer can be ventilated, air-cooled, or sealed?

Dry-type

What are the most common type of control transformer?

Dry-type, step-down units with secondary control circuits isolated from the primary to ensure maximum safety.

What is the chief use of capacitors?

Improve power factor.

What type of transformer contain a liquid with a fire point of not less than 300*C

Less- flammable liquid -insulated transformers

One affect cars by magnetic leakage in transformers is a _____________ ?

Lower secondary voltage

When AC flows through a transformer coil, a ___________ field is generated around the coils.

Magnetic

What causes voltage to be induced in a transformer?

Mutual induction.

What article states the specific rules for installation and protection of capacitors other than surge capacitors or capacitors that are part of another apparatus.

NEC Article 460

What NEC article covers the installation of separate resistors and reactors on electric circuits?

NEC Article 470

What NEC section requires nameplate info? What data?

NEC Sec 450.11, manufacture, rated kVA, rated frequency, primary and secondary voltage, impedance of transformer 25kVA and larger, required clearances for transformers with vented openings, and the amount and type of insulating liquid.

What NEC section requires that the phase bus bar or conductor having the higher voltage to ground be durably and permanently marked orange in color?

NEC Section 110.15

Which transformer core is the least expensive to manufacture?

Open Core

If one of the Transformers is damaged in a Delta system a _____________ configuration may be used temporarily carry the load.

Open Delta

The coil that receives energy from the line voltage?

Primary

Coil that delivers energy to the load?

Secondary

If there are more turns in the primary than the secondary?

Step Down

What is provided to either increase or decrease the secondary voltage?

Taps

Magnetic induction

The number of magnetic lines or the magnetic flux per unit of cross-sectional area perpendicular to the direction of the flux.

Reactance

The opposition to AC due to capacitance and / or the inductance

Ampere Turn

The product of amperes times the number of turns in a coil.

Induction

The production of magnetization or electrification in a body by the mere proximity of magnetize or electrified bodies,or the production of an electric current in a conductor by the variation of the magnetic field in its vicinity.

Flux

The rate of energy flow across or through a surface. Also a substance used to promote or facilitate soldiering or welding by removing surface oxides.

Turn ratio

The ratio between the number of turns between windings in a transformer; normally the primary to the secondary except for current transformers in which it is the ratio of the secondary to the primary.

Capacitance

The storage of electricity in a capacitor or the opposition to voltage change. Capacitance is measured in farads or microfarads

What are closed cores open cores and shell?

The three basic types of encore transformers.

What are primary windings secondary windings and the core?

The three parts of a basic transformer.

When the fuel from one coil cuts through the turns of a second coil, ______________ .

Voltage will be generated.