Comments on: Mains power transformer non-idealities https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/ All about electronics and circuit design Sat, 11 Jul 2026 20:00:25 +0000 hourly 1 http://wordpress.org/?v=3.9.14 By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1881250 Sun, 05 Jul 2026 13:37:36 +0000 https://www.epanorama.net/blog/?p=191578#comment-1881250 toroidal transformers tend take higher startup current on primary side when powered on than EI transformers. There are two things that cause the surge:
1. initial core magnetizing current
2. Small transformer losses (resistance, leakage inductance)
The 1 can burn primary fuse but does not affect the bridge rectifier.
The 2 causes high current flowing through rectifier on device starting, and cause rectifier failure if power supply was not properly engineered in the beginning (or the original transformer has been changed to different type).

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1865602 Wed, 19 Nov 2025 23:13:00 +0000 https://www.epanorama.net/blog/?p=191578#comment-1865602 What are distribution transformers?

Distribution transformers are electrical devices that step down medium voltage (like 11kV) to low voltage levels (like 400/230V) for safe and efficient use in homes, businesses, and industries. They’re the final stage in the power distribution network, playing a crucial role in supplying electricity to end-users. These transformers typically have a primary winding in a delta configuration and a secondary winding in a star configuration, allowing for both 3-phase and 1-phase power supply.

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1865551 Tue, 18 Nov 2025 15:40:27 +0000 https://www.epanorama.net/blog/?p=191578#comment-1865551 https://electronics.stackexchange.com/questions/301032/characteristics-of-ferrite-cores

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1865500 Mon, 17 Nov 2025 09:45:48 +0000 https://www.epanorama.net/blog/?p=191578#comment-1865500 https://shinenergy.net/guide-to-transformer-core-types-materials-and-applications/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1865499 Mon, 17 Nov 2025 09:45:10 +0000 https://www.epanorama.net/blog/?p=191578#comment-1865499 https://www.eevblog.com/forum/projects/what-core-alloys-are-most-typical-in-audio-and-power-(5060hz)-transformers/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1865498 Mon, 17 Nov 2025 09:44:49 +0000 https://www.epanorama.net/blog/?p=191578#comment-1865498 https://www.canwindg.com/a-news-demystifying-the-various-transformer-core-shapes

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1856540 Sat, 21 Jun 2025 12:01:45 +0000 https://www.epanorama.net/blog/?p=191578#comment-1856540 Open-Circuit and Short-Circuit Tests in Transformers
A transformer could be tested under no-load and full-load conditions to determine its turns ratio, regulation, and efficiency. However, without fully loading the transformer, it is possible to perform two tests (open-circuit and short-circuit) from which all the important data can be derived. In this article, learn how to analyze the results of open-circuit and short-circuit transformer tests to determine the component values of the transformer equivalent circuit.
https://eepower.com/technical-articles/open-circuit-and-short-circuit-tests-in-transformers/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1842258 Sun, 22 Dec 2024 11:34:47 +0000 https://www.epanorama.net/blog/?p=191578#comment-1842258 Erwin van Amelsfoort that’s a design problem in equipment design. Typically slightly undersized transformer and/or poor thermal design of the device.
Those built-in fuses in transformer are good safety protection against fire danger. Separate fuse gets often changed to wrong bigger current size by user if they fail.

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1842257 Sun, 22 Dec 2024 11:34:32 +0000 https://www.epanorama.net/blog/?p=191578#comment-1842257 From my personal experience (>25years of repairs) – embedded fuses are the best thing to prevent fire!!! I newer saw this fuse blown without real reason or in normal use. Yes, this is annoying, but if you do not want to have burning house replace them with new ones.

You’re wright, the should be forbidden…
The problem is when a divice gets warm during normal use, and you switch off and on, they blow up…

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2022/06/22/mains-power-transformer-non-idealities/comment-page-1/#comment-1840207 Sun, 01 Dec 2024 14:51:05 +0000 https://www.epanorama.net/blog/?p=191578#comment-1840207 https://zilogbob.com/blue2_ringer/blue2_ringer.htm

This new ring tester can test pretty-much all common inductors
including low-frequency mains and tube audio transformers
for shorted turns. At last it is available from EVB in Portugal.

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