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SPECIFYING YOUR IDEAL DC UPS
Microprocessor-based industrial controls—PLCs, industrial computers, HMI, drives, motion controllers and sensors—are the foundation of high productivity, quality and competitiveness. If there is one universal factor that can and will disrupt microprocessor-based controls and cause downtime, it is power quality. Since industrial electrical systems frequently experience voltage fluctuations, harmonic distortions, noise and short- or long-term power outages, it is essential to ensure maximum uptime by specifying an uninterruptible power supply (UPS) for the application.
Specifying the optimum UPS for a control system can be one of the most cost-effective investments available. But how do you do it? This white paper outlines the advantages and disadvantages of AC and DC UPSs, important things to know about batteries, key features for operations and diagnostics, and more important information to help you choose the best UPS for your purposes. The white paper is free, but registration is required. The direct link is at http://tinyurl.com/b7jaez4.
EGS Electrical Group
GUIDE TO POWER SYSTEMS PROTECTION
This 51-page PDF produced by IDC and Control covers concepts that are important and useful to engineers, scientists and technicians, independent of discipline. The substation automation system consists of intelligent electronic devices (IEDs), modern, third-generation microprocessor-based relays and/or remote terminal units (RTUs). PLCs also continue to play an important role in some systems. They receive analog inputs from current transformers (CTs), voltage transformers (VTs) and transducers in various switchgear panels, as well as digital inputs from auxiliary contacts, other field devices or IEDs, or the SCADA master. They are able to perform complex logical and mathematical calculations, and provide an output either to the SCADA Master, other field instruments or IEDs, or back to the switchgear to perform some command, for example open a circuit breaker.
This handbook covers power quality and how to maintain it, electrical protection of power systems and power substation automation. The booklet is free and downloadable, but registration is required. The direct link is at http://tinyurl.com/ae4gnd3.
REDUCING INPUT CURRENT HARMONICS
Non-linear loads are loads in which the current waveform does not have a linear relationship with the voltage waveform. Non-linear loads generate voltage and current harmonics, which can have adverse effects on equipment used to deliver electrical energy.
Power delivery equipment is subject to higher heating losses due to harmonic currents consumed by non-linear loads. Harmonics can have a detrimental effect on emergency or standby power generators, telephones and other sensitive electrical equipment. When reactive power compensation in the form of passive power factor improving capacitors are used with non-linear loads, resonance conditions can occur that may result in even higher levels of harmonic voltage and current distortion, thereby causing equipment failure, disruption of power service and fire hazards in extreme conditions.
This white paper discusses ways to control and reduce these dangerous harmonics. This paper is free with registration and downloadable at www.controlglobal.com/whitepapers/2010/035.html.
Yaskawa America Inc.