All Exams Test series for 1 year @ ₹349 only
Question

Which power loss is assessed by open-circuit test on transformer?

This question was previously asked in
RRB NTPC 2024 Undergraduate CBT 1 Question Paper (29-Aug-2025) (Shift 1)
The correct answer is
Core loss

The open-circuit test on a transformer is performed to determine the core losses. These losses are primarily due to hysteresis and eddy currents within the transformer's core material. During the open-circuit test, the high-voltage side of the transformer is energized at rated voltage, while the low-voltage side is left open. This essentially eliminates the copper losses (I²R losses in the windings) as there's negligible current flowing in the secondary winding. The input power measured under these conditions is almost entirely consumed by the core itself, representing the core losses.

Therefore, the correct answer is Core loss.

Let's examine why the other options are incorrect:

  • Friction loss: Friction losses are mechanical losses associated with bearings and other moving parts in a transformer. The open-circuit test doesn't measure these mechanical losses.
  • Copper loss: Copper losses are I²R losses in the windings, directly proportional to the square of the current. The open-circuit test minimizes current flow, and hence these losses are negligible.
  • Winding loss: This is another term for copper loss, and is negligible during the open-circuit test.
Was this answer helpful?

Similar Questions

  1. What will be the eddy current loss if the supply frequency of a transformer becomes double?

Important Questions from Transformer Core Losses

  1. Eddy current loss in a transformer can be reduced by _________.

  2. Out of the following, which loss is also a category of magnetic losses?

  3. Transformer at no-load behaves like:

  4. In transformer, hysteresis loss depends on:

  5. How can eddy current loss be minimised in Transformer?

Need Expert Advice?
Test Series
RRB ALP img
Railways
RRB ALP 2026 Mock Test series
1035 Tests 1 Tests Free
1697 Attempts
4.3(257)
English, Hindi

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App