Variable Frequency Drive
Variable frequency drives are widely used to control the speed of ac motors. This note looks at the mechanisms which enable drive units to control the...
DC Component of Asymmetrical Faults
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 ...
How to Size Power Cable Duct
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...
Periodic Electrical Installation Inspection – What to Inspect?
This is the second post in a series of two on periodic electrical inspections. In the first post, I discussed how often inspections should be carried out...
Three Phase Current - Simple Calculation
The calculation of current in a three phase system has been brought up on our site feedback and is a discussion I seem to get involved in every now and...
Software Usage Guidelines
Using software in our work is essential for most of us and we are becoming even more dependant on it's use. While software is a great asset, many times...
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...
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...
How Electrical Circuits Work
If you have no idea how electrical circuits work, or what people mean then they talk about volts and amps, hopefully I can shed a bit light. I’m intending...
Batteries
A battery consists of one or more cells, each of which use stored chemical energy to produce electrical energy, There are many types of cells and these...