Licensed Electrical Contractor Transformers and Transformer Calculations 1

Question 1

A transformer has 480 primary turns and 120 secondary turns. What is the turns ratio?

Accepted Answer

4:1

Answer

The turns ratio is primary turns divided by secondary turns: 480 / 120 = 4:1.

Question 2

A transformer has a primary voltage of 480V and a turns ratio of 4:1. What is the secondary voltage?

Accepted Answer

120V

Answer

Secondary voltage = Primary voltage / turns ratio = 480V / 4 = 120V.

Question 3

Which type of transformer provides electrical separation between its primary and secondary windings with no direct electrical connection?

Accepted Answer

Isolation transformer

Answer

Isolation transformers separate primary and secondary windings to prevent direct electrical connection, protecting equipment from power line disturbances.

Question 4

What does the kVA rating on a transformer nameplate represent?

Accepted Answer

The transformer's apparent power capacity

Answer

The kVA rating indicates the apparent power (kilovolt-amperes) the transformer can continuously deliver without exceeding its temperature rating.

Question 5

In an ideal transformer, when voltage is stepped up from primary to secondary, what happens to the current?

Accepted Answer

Current decreases proportionally

Answer

In an ideal transformer, apparent power in equals apparent power out; as voltage increases, current must decrease proportionally to maintain constant power.

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Transformers and Transformer Calculations 1