Cost Performance and Time
Often us engineers get so bogged down in equations, using software, producing drawings and writing specifications that this becomes the sole focus. ...
IEC 61439 Verification Methods
The (relatively new) switchgear and control gear standard, IEC 61439 'Low-voltage switchgear and controlgear assemblies' has three methods which can be...
Restricted Earth Fault Protection
The windings of many medium and small sized transformers are protected by restricted earth fault (REF) systems. The illustration shows the principal of...
IEC Reference Designations
The IEC publishes a series of documents and rules governing the preparation of documents, drawings and the referencing of equipment. Depending on country...
Lead us, Warleader
Delum, who had watched all in silence, his face empty of expression, now spoke in turn. ' "Lead us, Warleader, into glory."'
Reading is something I do...
Understanding Circuit Breaker Markings
IEC 60947 is the circuit breaker standard and covers the marking of breakers in detail. Any manufacturer following this standard should comply with 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 ...
RLC Circuit, Resistor Power Loss - some Modelica experiments
Modelica is an open source (free) software language for modelling complex systems. Having never used it before, I thought I would download a development...
Understanding electric motor insulation & temperature
Anyone specifying or using electric motors should have a basic understanding how the insulation is related to temperature. Three classes of insulation...
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...