Electricity is the movement of charge. No matter how the charge is created, chemically (like in batteries) or physically (friction from socks and carpet), the movement of the discharge is electricity. The flow of electrical charge is referred to as electric current. Simple Electrical Circuits An Electric Circuit is a closed path for transmitting an electric current through the medium of electrical and magnetic fields. The flow of electrons across the loop constitutes the electric current. Electrons enter the circuit through the “Source,” which can be a battery or a generator. Series Circuits When several elements are connected in linear series with an energy source, the circuit is known as a series circuit. For a series circuit, the same amount […]
Electrical Distribution
Basic Power Distribution
Design engineers and technicians use schematics to build and troubleshoot complex circuits, while plant operators use single-line and riser diagrams to facilitate switching operations within their distribution system. Knowing how to read and interpret various types of electrical drawings is an essential skill that all electrical workers must posses to effectively carry out their tasks. The symbols and lines within an electrical drawing speak a language that everyone involved must understand in order to design, build, and troubleshoot electrical systems. One-Line Diagram These drawings show the flow of electrical power or the course of electrical circuits and how they are connected. they should show all of the major components in the power system and list all important ratings. These drawings […]
Switchgear Basics
Medium and large-sized facilities commonly use switchboards to safely distribute power to transformers, panelboards, control equipment, and, ultimately, to system loads. Substations and switchgear in an electrical system perform the functions of voltage transformation, system protection, power factor correction metering, and circuit switching. Electrical power apparatus, such as transformers, regulators, air switches, circuit breakers, capacitors, and lightning arresters comprise the components necessary to perform these functions. Basic Components Frame – The frame of the switchboard houses and supports the other components. Bus – Metal bars mounted inside the switchboard to conduct power to the switchboard’s devices. Phase arrangement per NEMA is ABC left to right, and top to bottom. Instrumentation – This instrumentation often includes one or more meters designed […]
Circuit Breaker Basics
Circuit breakers are critical links in a fault-clearing situation. When a fault occurs on the electrical system, the associated current must be interrupted quickly and reliably to prevent catastrophic damage to equipment and nearby personnel. Basic Components Frame – Outer enclosure for other components. Operating Mechanism – Responsible for the mechanical charge, trip, and close cycle. Primary Contacts – All circuit breakers have contacts, and when the contacts separate during a fault clearing operation, they draw an arc. The electric arc forms between the contacts and is drawn out in length as the contacts open. Arcing Contacts – Arcing contacts are designed to make-before and break-after the main contacts. This helps keep high temperatures away from the main contacts which […]
Transformer Basics
Transformers are mainly used to step down a higher distribution level voltage to a lower utilization level. They are vital links in electrical power systems and are among the most reliable components in the system. Transformers can be divided into two general categories according to their insulating medium and construction: liquid-filled and dry-type. Components Core – Made of thin iron laminations. The purpose of the iron core is to channel the magnetic flux 1 generated by the current flowing around the primary coil, so that as much of it as possible also links the secondary coil. Coil – The windings are manufactured from copper or aluminum conductors, separated by layers of insulation. Each conductor is formed with precision around a […]
Electric Motors and Control Systems
An electric motor is the workhorse that converts electrical energy into mechanical energy using the principles of electromagnetism. Magnetic fields created by electrical charges are the driving force behind motors which generate the torque required to perform useful work. Components Rotor – The rotor is the moving part It turns the shaft that delivers the mechanical power. Stator (and Stator Core) – The stator is the stationary part of the motor’s electromagnetic circuit and usually consists of either windings or permanent magnets. The Bearings – The rotor is supported by bearings, which allow it to turn on its axis. Windings – Windings are wires that are laid in coils, usually wrapped around a laminated soft iron magnetic core so as […]
UPS System Basics
Uninterruptible Power Supply (UPS) Systems are used extensively in critical environments to support sensitive electrical equipment when there is a power loss or a significant change in the primary power source. Backup power is provided to the UPS by a string of batteries that can instantly support the load when it detects a loss or other interruption in the available power. Once a power anomaly has been detected, the UPS control will transfer over to DC battery power and convert the output to AC via an inverter. When normal power is restored, the UPS will switch back to normal and use available power to recharge the batteries. General Functions of a UPS Absorb relatively small power surges. Smooth out noisy […]
Direct-Current Systems (Batteries)
Batteries and battery systems are the most important component of any UPS system. UPS batteries are the engine, or the power source, if the utility power fails or some type of power anomaly is experienced. Batteries are the most common failure/problem within any UPS system. Batteries can also be found in emergency generators and substation control power. VRLA (Valve Regulated Lead Acid) Valve Regulated Lead Acid UPS batteries, are also sometimes called “maintenance free” batteries. The term “maintenance free” comes from the fact that you are not able to add fluid to the battery. The term “valve regulated “means these batteries limit the inflow and outflow of gas to the cell. VRLA batteries are the most popular UPS battery type […]
Emergency Power Distribution Basics
Emergency Generator A diesel generator, also known as a Genset, is a piece of equipment that consists of a diesel engine and an electric generator/alternator. These two items work together to convert diesel fuel into electrical energy. Diesel burns at a much higher temperature compared to other fuel sources making it more efficient and powerful. The engine converts the fuel into mechanical energy. This energy powers the alternator by spinning the alternator rotor which converts the mechanical energy into electrical energy. A diesel standby generator can run for hours, days, and even weeks with the proper maintenance and fuel supply. Generators come in a variety of sizes and strengths depending on their purpose. The two main types of generators are […]
Basics of Electrical Safety
Electricity has long been recognized as a serious workplace hazard, exposing employees to electric shock, electrocution, burns, fires, and explosions. Hundreds of deaths and thousands of injuries occur each year on the job due to electrical shock and arc flash, yet almost all of these tragic events are preventable. In addition to being properly qualified for the task at hand, personal protective equipment (PPE), including arc flash rated clothing, can provide additional safeguards against the hazards posed by working around electrical energy. NFPA 70E NFPA 70E covers electrical safety requirements for employees, including the proper selection, use, and care of personal protective equipment (PPE). The document describes safe work practices for electrical construction and maintenance but does not specify how […]