Circuit breaker design for safety in underground mining applications

  Circuit breaker applications in underground mining and recommended methods to maximise the effectiveness of these protective devices In mining, the underground assembly or power centre is engineered to transform and distribute electrical power brought underground. This assembly typically includes a medium-voltage incoming circuit breaker or switch with current-limiting fuse (see Fig 1). The device […]

Selection of AC induction motors for cement plant applications

The selection of AC induction motors for cement mill applications, with reference to fan, kiln and vertical mill applications. Cement plant applications present an immense matrix of application criteria to specify, design and build motors properly. Operating conditions Basic motor specifications begin with determining the motor nameplate horsepower (hp) and revolutions per minute (rpm). These […]

Clever pumping: making water industry’s pumps intelligent

  Climate change, increasing water demands due to global urbanisation, and the legal obligations of the EU’s Water Framework Directive are all making the water sector an attractive arena for technologies that can help reduce costs and contribute to reducing the effects of climate change. It is against this backdrop that the demand for intelligent […]

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 […]

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 […]

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 […]