The ABCs of multimeter safety

  Often, users accidentally subject their multimeters to much higher voltage than they think they are measuring. This submits the units to momentary high-voltage spikes, causing them to fail. The possibilities of transient overvoltages increase as distribution systems and loads become more complex. Motors, capacitors and power conversion equipment such as variable speed drives (VSDs) […]

Some developments in winder brake control

  From the ICMEESA archive Methods of control for low and high pressure hydraulic braking systems which have been applied successfully to a number of hoists in South Africa. This article describes new and simplified control systems for low pressure and high pressure hydraulic braking systems with emphasis on air brake and low pressure oil […]

How to size a generator set

  Many factors influence generator set sizing, making it time consuming to manually calculate required generator capacity. Parameters that determine the required generator set size include minimum generator set load; maximum allowable step voltage dip and step frequency dip; altitude and temperature; duty cycle, fuel, phase, frequency and voltage. Sizing software, such as Cummins Power […]

Bloodhound SSC: a supersonic engineering marvel

  A hybrid jet-and-rocket powered vehicle will fire up its 135 000 hp engines to break the sound barrier and the world record alike in a 1600 km/h race at Hakskeen Pan, South Africa. The 14 m, 7 tonne Bloodhound supersonic car (SSC) was designed and is being built by the Bloodhound Project, described as […]

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 […]