TL;DR

Learn transformer sizing, connection methods, and voltage regulation principles. Transformer applications appear frequently on electrician licensing exams.

By Valenke Exam Prep Team·Last updated 2026-06-03

Free Transformer Calculations Practice Questions

Journeyman Electrician License Exam · Motors & Transformers

This module covers Transformer Calculations as part of the Motors & Transformers section, testing your understanding of core concepts and their practical application.

Exam	Journeyman Electrician License Exam
Pass Rate	55%
Duration	240 minutes
Module	Transformer Calculations

Why Transformer Calculations matters

Transformer Calculations is one of the most tested areas because medication errors are among the most preventable causes of patient harm.

Sample Practice Questions (5)

1. A single-phase transformer has a 4:1 turns ratio (primary:secondary). The primary is connected to 480V, and the secondary supplies a 10-ohm resistive load. What is the primary current?

3 amps
12 amps
48 amps
0.75 amps

2. A delta-wye transformer bank consists of three single-phase, 50 kVA transformers. The primary is 480V delta, and the secondary is 208Y/120V. What is the total 3-phase kVA capacity and the secondary line current?

150 kVA, 416.5 amps
100 kVA, 277.7 amps
150 kVA, 625 amps
50 kVA, 138.8 amps

3. A 3-phase, 150 kVA, 480V delta primary to 208Y/120V wye secondary transformer is at full load. What are the primary and secondary line currents?

Primary: 180.4A, Secondary: 416.5A
Primary: 312.5A, Secondary: 720.9A
Primary: 104.2A, Secondary: 240.8A
Primary: 208.3A, Secondary: 312.5A

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4. In a delta-connected 3-phase system, what is the relationship between line current (IL) and phase current (IP)?

IL = IP
IL = IP × √3
IL = IP / √3
IL = IP × 3

5. A single-phase, 25 kVA transformer has a 480V primary and a 240/120V secondary. What is the full-load primary current?

52.1 amps
104.2 amps
208.3 amps
30 amps

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Frequently Asked Questions

How many Transformer Calculations questions are on the Journeyman Electrician License Exam?▼

The Motors & Transformers section, which includes Transformer Calculations, typically represents a significant portion of the exam. Focus on understanding core concepts rather than memorizing exact question counts, as the exam uses adaptive testing.

What is the best way to study Transformer Calculations?▼

Practice solving calculation problems daily rather than just reading formulas. Work through problems step-by-step, check your units, and time yourself to build speed and accuracy under exam conditions.

Is Transformer Calculations one of the harder sections on the exam?▼

Yes, Transformer Calculations is considered challenging because it requires applying multiple code articles simultaneously. Practice with scenario-based questions that require you to reference specific NEC requirements.