The energy efficiency of over-current protective devices

  A test programme to quantify energy losses in over-current protective devices (OCPDs) shows that switches and fuses are less energy-efficient compared with equivalent circuit breakers carrying the same load currents. The devices in an electrical distribution system are a critical part of the facility’s infrastructure. These devices include transformers, conductors and over-current protective devices. […]

Improving motor efficiency

  Some 20% of the estimated 65% of industrial energy used by electric motors is lost by wasteful throttling mechanisms, making it essential to reduce the energy appetite of motors. Energy consumption by electric motors can be reduced in two main ways – efficient control of the speed at which they run, and making the […]

Fundamentals of lighting design

  A basic guide to lighting and lighting design explaining variables such as working plane, mounting height; depreciation factors; coefficient of utilisation and reflectance factors. The following basic design concepts should generally be considered when designing a lighting solution for either indoor or outdoor applications: Whether the lighting will be installed in a safe or […]

How smart seals extend the service life of luminaires

  “Intelligent seals” prevent the ingress of water and contaminants into luminaires’ housing while allowing pressure to equalise in both directions. Standard neon tubes and energy-saving lamps are increasingly replaced by LED lamps. With a very long service life, these lamps are extremely reliable and environmentally friendly. To achieve this service life, housings must be […]

Optical calculations for SSL applications

  Rough calculations are useful for estimating LED type and count at the beginning of a project. This article provides some typical techniques for calculating optical quantities and estimating LED count. A basic understanding of optical principles is necessary before any calculations can be started. The most important principles for SSL applications are reflection, refraction […]

The advantages of decentralised control

  An overview of decentralised motor control systems, their applications, savings incurred, programming, motor brake control, reliability and commissioning. In decentralised control systems, motor control functions are removed from a central control cabinet and distributed out on a machine so that control devices are located closer to the machine’s motors. This form of control was […]

Ventilation circuits applied to cylindrical rotor synchronous machines

  The main ventilation arrangements for cylindrical rotors in synchronous machines to dissipate heat from the stator and rotor windings. Cylindrical rotor synchronous machines are characterised by their rugged pole design. The poles are built flush with the rotor surface and their windings lie in slots in the rotor periphery, and are also called non-salient […]

Some interesting features of a modern power station – Part 2

  From the ICMEESA archive A closer look at South Africa’s most modern power plant, Arnot, focusing on its coal and ash handling plant; boilers; water plant; generators and control and monitoring, among others. Part 1 of this article discussed Arnot power station’s coal and ash handling plant; its boilers; circulation system; superheaters and reheaters […]

Preventing “accidents” in construction

  The recent Tongaat Mall collapse led to a media frenzy, only to fizzle out over time. The Department of Labour is investigating the “accident” and the question now is, “what will the findings be?” Fatalities, injuries, disease, and inadequate health and safety (H&S) measures, including non-compliance, will continue to occur until the South African […]

The causes and effects of inter-system ground noise

  Non-isolated computer equipment connections such as RS-232, parallel and USB can cause inter-system ground noise which AC power protection equipment cannot correct. The uninterruptible power supply (UPS) system is essential to any business computer system but it cannot protect the computer completely from all power related problems. Energy management company Schneider Electric has identified […]