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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...

How to Check a Circuit is Dead

If you want to check a circuit is dead (not live), you should always use the three point method. First check a known live circuit, then check the dead...

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...

Fault Calculations - Typical Equipment Parameters

A frequent problem in fault calculations is the obtaining of equipment parameters.  While it is always preferable to use the actual parameters of the equipment...

Motor Starting - Introduction

Motor starting and its associated problems are well-known to many people who have worked on large industrial processes. However, these things are, of course...

Introduction to Current Transformers

Current transformers (CTs) are used to convert high level currents to a smaller more reasonable level for use as inputs to protection relays and metering...

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...

110 or 230 Volts

I've been considering a blog on the 110 or 230 Volt issue for a while.  While browsing the Internet I came across a great summary by Borat over at  engineering...

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...

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...

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