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MIT OpenCourseWare

MIT OpenCourseWare, makes the materials used in teaching all MIT subjects available on the Web, free of charge, to any user in the world.

Wiki Depreciation

We have had the Wiki with us for a long time now, but at last I have decided to say bye bye – more details on why below.

IEC 61439 - The Switchgear Standard

The new standard IEC 61439 replaces the old 60439. Compared to the old standard, the new 61439 is a more clearly defined and takes into account the assembly...

Low Voltage Circuit Breakers

Circuit breakers are switching devices whose primary function is to isolate parts of an electrical distribution system in the even of abnormal conditions...

Understanding Motor Duty Rating

One of the comments on my Motor Starting Series was asking for something on duty cycles. Here it is. As a purchaser of a motor, you have responsibility...

Dielectric loss in cables

Dielectrics (insulating materials for example) when subjected to a varying electric field, will have some energy loss.   The varying electric field causes...

Why a Sine Wave?

I received this question by email a few weeks. First thoughts was that it is a product of the mathematics of rotating a straight conductor in a magnetic...

What is an Open Delta Transformer

In three phase systems, the use of transformers with three windings (or legs) per side is common.  These three windings are often connected in delta or...

Why is electricity so hard to understand?

It's been a busy few months on different projects or busy couple of decades depending on how I look at it. I can say that on the odd (frequent) occasion...

Introduction to Traction Substations

Following on from my post on railway electrification voltages, I thought an introduction to traction substations would be a good idea. Traction substations...

Have some knowledge to share

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By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note