Journeyman Electrician Practice Exam

Disable ads (and more) with a membership for a one time $4.99 payment

Prepare for the Journeyman Electrician Exam. Test your skills with multiple-choice questions designed to help you succeed. Each question comes with hints and detailed explanations to assist in your study process.

Practice this question and more.

What is the full-load current rating of a 75 kVA, three-phase transformer with a 208Y/120 volt secondary?

150 amperes
175 amperes
208 amperes
250 amperes

The correct answer is: 208 amperes

To determine the full-load current rating of a 75 kVA, three-phase transformer with a 208Y/120 volt secondary, you use the formula for full-load current in a three-phase system: Full Load Current (I) = Power (kVA) × 1000 / (√3 × Voltage) Given that the power rating is 75 kVA and the voltage is 208 volts (the line-to-line voltage in a three-phase system), you can plug the values into the formula: I = 75 × 1000 / (√3 × 208) First, calculate the denominator: √3 ≈ 1.732 So, 1.732 × 208 ≈ 360.736 Now calculate the full-load current: I = 75000 / 360.736 ≈ 208.2 This rounds to approximately 208 amperes. Thus, the calculation confirms that the full-load current rating of the transformer is indeed around 208 amperes, making this the correct answer. This showcases the application of fundamental electrical principles and calculations used in the field of electrical engineering and practical transformer operation.