EE 8 - Transformers

Transformer

A static device used to transfer electrical energy from one AC circuit to another without changing frequency

Primary winding

The winding of a transformer that is connected to the AC supply

Secondary winding

The winding of a transformer that is connected to the load

Step down transformer

A transformer used to reduce the voltage level is called a _

Mutual induction

The working principle of a transformer where voltage is induced in the secondary coil due to flux from the primary

No

Can a transformer operate on a Direct Current (DC) source?

Laminated steel

The transformer core is constructed from _ sheets to reduce eddy current loss

Core type transformer

The type of transformer construction where the winding encircles the core

Shell type transformer

The type of transformer construction where the core encircles most of the windings

EMF equation

E=4.44fNΦm​ is known as the _ of a transformer

Transformation ratio

The ratio of secondary voltage to primary voltage (K=V2​/V1​) is called the _

Isolation transformer

A transformer where K=1 (input voltage equals output voltage) is often called an _

kVA (Volt-Ampere)

Transformers are rated in _ rather than kW because losses depend on voltage and current

Copper losses

Power losses that occur in the winding resistances (I2R) are called _

Eddy current

Iron losses (or core losses) consist of Hysteresis losses and _ losses

Hysteresis loss

The loss that is minimized by using steel with high silicon content for the core

Iron loss

A transformer operates at maximum efficiency when copper loss equals _

Voltage regulation

The change in secondary terminal voltage from no load to full load is defined as _

0%

Ideally, the voltage regulation of a transformer should be _

Autotransformer

A specialized transformer with only one winding that serves as both primary and secondary

Less

Compared to a conventional two-winding transformer, an autotransformer requires _ copper

100%

Ideally, the efficiency of a transformer is assumed to be _

Delta-Star connection

The three-phase transformer connection most commonly used for distribution applications

Coolant

Inside the transformer tank, oil acts as both an insulator and a _

Step up

If the transformation ratio K>1, the transformer is a _ transformer

Oil

Inside the tank of the transformer, the assembly of the transformer is immersed in _____ which acts as an insulator as well as coolant.

low, high

In a Core Type Transformer, the _ voltage coil is placed inside near the core, while the _ voltage coil surrounds the low voltage coil

Double

A Shell Type Transformer has a _ magnetic circuit

3

Number of limbs of a Shell Type Transformer

central limb

Both the windings of a Shell Type Transformer are placed on the _.

Multilayer disc type or sandwich coils

The coils of a Shell Type Transformer used are generally _.

Between two low voltage coils

In a Shell Type Transformer, where are the high voltage coils located?

Near the top and bottom yokes

In a Shell Type Transformer, where are the low voltage coils located?