Notes

Electromagnetic Fields - Exposure Limits

By Steven McFadyen on 6/28/2014 6:00 PM

Exposure to time varying magnetic fields, from power frequencies to the gigahertz range can have harmful consequences. A lot of research has been conducted into identifying these effects and de... read more..

DC Component of Asymmetrical Faults

By Steven McFadyen on 1/9/2013 6:52 PM

The image (reproduced from IEC 60909) shows a typical fault in an ac system. From the illustration it can seen that there is an initial dc component (i_d.c.). This initial dc compo... read more..

Induction Motor Equivalent Circuit

By Steven McFadyen on 5/13/2014 1:19 PM

Induction motors are frequently used in both industrial and domestic applications. Within the induction motor, an electrical current in the rotor is induced by a varying magnetic field in the s... read more..

Photovoltaic (PV) - Electrical Calculations

By Steven McFadyen on 7/11/2013 2:46 PM

Photovoltaic (PV) cells (sometimes called solar cells) convert solar energy into electrical energy. Every year more and more PV systems are installed. With this growing application, it's ... read more..

How D.C. to A.C. Inverters Work

By Steven McFadyen on 4/22/2014 1:19 PM

Traditionally generation of electricity has involved rotating machines to produce alternating sinusoidal voltage and current (a.c. systems). With the development of power electronics during the last ... read more..

The dc resistance of conductors

By Steven McFadyen on 1/5/2012 2:14 PM

This is the first of two posts on the resistance of conductors. In the next post I will look at the ac resistance, including skin effect and we deal with this. To get started, this post will look at the... read more..

How to Size Power Cable Duct

By Steven McFadyen on 11/24/2011 10:09 AM

Some colleagues had an issue earlier in the week on sizing conduits to be cast in concrete for some power cables . It became clear that none of us had a clear idea on an approved method. In the end w... read more..

How to Size Current Transformers

By Steven McFadyen on 11/7/2011 11:48 AM

The correct sizing of current transformers is required to ensure satisfactory operation of measuring instruments and protection relays. Several methods exist to size current transformers. This note will... read more..

Back to Basics - Ohm’s Law

By Steven McFadyen on 10/21/2011 2:02 PM

Electrical engineering has a multitude of laws and theorems. It is fair to say the Ohm's Law is one of the more widely known; it not the most known. Developed in 1827 by Georg Ohm the law defines the re... read more..

Alternating Current Circuits

By Steven McFadyen on 4/3/2012 1:29 PM

Alternating current (a.c.) is the backbone of modern electrical power distribution. In this article I’ll be pulling some of the more important concepts together. It is a work in progress and I’ll be add... read more..

Laplace Transform

By Steven McFadyen on 4/23/2012 2:05 PM

Laplace transforms and their inverse are a mathematical technique which allows us to solve differential equations, by primarily using algebraic methods. This simplification in the solving of equat... read more..

UPS Battery Sizing

By Steven McFadyen on 4/8/2012 1:36 PM

Various techniques exist to enable the correct selection of batteries for UPS applications. The procedure described below is one of the more common. It is also possible to use the IEEE 485 method ... read more..

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Alternating Current Circuits

Alternating current (a.c.) is the backbone of modern electrical power distribution. In this article I’ll be pulling some of the more important concepts...

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...

Generator Sizing & Operation Limits

When selecting a generator, there are inherent limits on the active and reactive power which can be delivered. Generators are normally sized for a certain...

New Mail Chimp

We've been sending out Newsletters on a regular basis for a few weeks now. To do this we have been using Google's Feedburner service. While Feedburner...

Back to basics - the Watt (or kW)

When thinking about watts (W) or kilowatt (kW = 1000 W) it can be useful too keep in mind the fundamental ideas behind the unit. Watt is not a pure electrical...

Questions - Reputation and Privilege

Our question and answer system while letting you do exactly what it says, is much more. It is a dynamic user driven system, where our users not only ask...

IEC Document Designation

Often document control is dictated by project requirements, for example a particular organisation may have an existing numbering system. Existing company...

GE's Shingijutsu Factory

GE's latest thinking on product manufacturing is he Shingijutsu philosophy or Lean production system. They have started applying this at the Louisville...

How to Calculate Motor Starting Time

Request to look at induction motor starting time have come up a few times on the site. Hopefully in this post, I give you guys some idea on how to calculate...

UPS Battery Sizing

Various techniques exist to enable the correct selection of batteries for UPS applications. The procedure described below is one of the more common. ...

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