How to keep VFDs and motors running

  Applied to blowers and pumps, VFDs offer energy savings and, in mechanical applications, allow fine adjustments which are impossible with other methods. Yet they are not simple plug-in-and-forget devices. Variable frequency drives (VFDs) are full of electronics and are susceptible to many problems, from incoming power disturbances to environmental hazards and incorrect use – […]

Arc flash mitigation and arc-resistant switchgear

Application of arc-resistant switchgear to help mitigate arc flash hazards can be a very effective way to enhance safety for electrical workers. Not only the selection of protective device types, but also selecting the settings for adjustable devices is important in the mitigation of arch flashing. Settings must be chosen to protect equipment properly while […]

An improved approach for connecting VSDs and electric motors

  Motor winding insulation can deteriorate quickly and the motor may fail when variable speed drives are connected to motors by long cable lengths. Within the VSD, AC supply voltage is converted into DC by means of a rectifier. DC power contains voltage ripples which are smoothed using filter capacitors. This section of the VSD […]

Electrical, insulation and thermal measurements for motors and drives

  Electrical, insulation resistance and thermal measurement are three tests which can troubleshoot motors, drives and associated electrical panels and prolong their operational lifetime. Used together, thermal imagers can detect potential problems and insulation resistance, while electrical tests can determine the cause. Handheld thermal imagers can collect heat signatures from a range of motors, from […]

Sustainable shaft grounding with variable frequency drives

  Currents induced on motor shafts by variable speed drives (VFDs) can wreak havoc with motor bearings, shortening motor life dramatically and causing costly repairs. A reliable method of shaft grounding is essential to mitigate these currents and realise the full potential of VFDs. In the field of flow control, the potential for increased efficiency […]

Switchgear for power factor correction systems

  The importance of differentiating between various circuit types or capacitor assignments to inductive loads when implementing power factor correction (PFC). A differentiation is made between individual PFC and group PFC. With individual PFC, the capacitor is assigned individually or switched to a load. With group PFC, the power factor of a load group is […]

Clever pumping: making the water industry’s pumps intelligent

  Climate change, increasing water demands 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 process control equipment is […]

Maximising surge protection safety

  Servicing surge protection devices (SPDs) safely without impacting critical operations has traditionally been difficult but a new generation SPDs is solving this problem. Servicing traditional SPDs poses serious risks to maintenance personnel and mission-critical workloads. If the SPD has an internal disconnect, power on the line side of the disconnect continues to flow even […]

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 […]