Electric power travels from the power station through high-voltage transmission lines. The idea behind high-voltage transmission is minimal current flow as energy is carried very efficiently via coaxial cable in a magnetic field. A single transmission line typically carries enough power for multiple homes or businesses, and can be thought of as an "energy resevoir". Outside homes and businesses a "step-down" transformer converts the energy transmission to relatively low-voltage, requiring high-current flow largely within the conductor material. This method of conducting electricity is relatively inefficient or "lossy". For example, typically as much energy is lost in the last few hundred feet distance from the step-down transformer to your home as through the miles of coaxial cable from the power station to the step-down transformer!
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Contact us for BIG Discounts on large orders. Three-phase electric power is a common method of electric power transmission.
It is a type of polyphase system mainly used to power motors and many other devices. A three-phase system uses less conductor material to transmit electric power than equivalent single-phase , two-phase, or direct-current systems at the same voltage.
In a three-phase system, three circuit conductors carry three alternating currents of the same frequency which reach their instantaneous peak values at different times. Taking one conductor as the reference, the other two currents are delayed in time by one-third and two-thirds of one cycle of the electrical current.
This delay between "phases" has the effect of giving constant power transfer over each cycle of the current, and also makes it possible to produce a rotating magnetic field in an electric motor.
Three phase systems may or may not have a neutral wire. A neutral wire allows the three phase system to use a higher voltage while still supporting lower voltage single phase appliances. In high voltage distribution situations it is common not to have a neutral wire as the loads can simply be connected between phases phase-phase connection.
Three phase has properties that make it very desirable in electric power systems. First, the phase currents tend to cancel out one another, summing to zero in the case of a linear balanced load. This makes it possible to eliminate the neutral conductor on some lines; all the phase conductors carry the same current and so can be the same size, for a balanced load. Second, power transfer into a linear balanced load is constant, which helps to reduce generator and motor vibrations.
Finally, three-phase systems can produce a magnetic field that rotates in a specified direction, which simplifies the design of electric motors. Three is the lowest phase order to exhibit all of these properties. Most domestic loads are single phase. Generally three phase power either does not enter domestic houses at all, or where it does, it is split out at the main distribution board.
At the power station, an electrical generator converts mechanical power into a set of alternating electric currents, one from each electromagnetic coil or winding of the generator.
The currents are sinusoidal functions of time, all at the same frequency but offset in time to give different phases. In a three-phase system the phases are spaced equally, giving a phase separation of one-third cycle. Generators output at a voltage that ranges from hundreds of volts to 30, volts. At the power station, transformers "step-up" this voltage to one more suitable for transmission.
After numerous further conversions in the transmission and distribution network the power is finally transformed to the standard mains voltage i. The power may already have been split into single phase at this point or it may still be three phase.
Where the stepdown is 3 phase, the output of this transformer is usually star connected with the standard mains voltage V in North America and V in Europe and Australia being the phase-neutral voltage. Another system commonly seen in North America is to have a delta connected secondary with a center tap on one of the windings supplying the ground and neutral.
This allows for V three phase as well as three different single phase voltages V between two of the phases and the neutral, V between the third phase known as a high leg and neutral and V between any two phases to be made available from the same supply. Single-phase loads may be connected to a three-phase system, either by connecting across two live conductors a phase-to-phase connection , or by connecting between a phase conductor and the system neutral, which is either connected to the center of the Y star secondary winding of the supply transformer, or is connected to the center of one winding of a delta transformer Highleg Delta system.
Single-phase loads should be distributed evenly between the phases of the three-phase system for efficient use of the supply transformer and supply conductors.
The line-to-line voltage of a three-phase system is v3 times the line to neutral voltage. In multiple-unit residential buildings in North America, lighting and convenience outlets can be connected line-to-neutral to give the V distribution voltage V utilization voltage , and high-power loads such as cooking equipment, space heating, water heaters, or air conditioning can be connected across two phases to give V.
This practice is common enough that V single-phase equipment is readily available in North America. Where three phase at low voltage is otherwise in use, it may still be split out into single phase service cables through joints in the supply network or it may be delivered to a master distribution board breaker panel at the customer's premises. The power transmission grid is organized so that each phase carries the same magnitude of current out of the major parts of the transmission system.
The currents returning from the customers' premises to the last supply transformer all share the neutral wire, but the three-phase system ensures that the sum of the returning currents is approximately zero. The delta wiring of the primary side of that supply transformer means that no neutral is needed in the high voltage side of the network. If the supply neutral of a three-phase system with line-to-neutral connected loads is broken, generally the voltage balance on the loads will no longer be maintained.
Lightly-loaded phases may see up to sqrt 3 as much voltage as rated, causing overheating and failure of many types of loads. For example, if several houses are connected to a common transformer on a street, each house might be connected to one of the three phases. If the neutral connection is broken at the transformer, all equipment in a house might be damaged due to over voltage. Such events are hard to track down if one does not realize this possibility. Conservative distribution design will take this problem into account to ensure the neutral connections are as reliable as any of the phase connections.
The rotating magnetic field of a three-phase motor. The most important class of three-phase load is the electric motor. A three phase induction motor has a simple design, inherently high starting torque, and high efficiency. Such motors are applied in industry for pumps, fans, blowers, compressors, conveyor drives, and many other kinds of motor-driven equipment.
A three-phase motor will be more compact and less costly than a single-phase motor of the same voltage class and rating; and single-phase AC motors above 10 HP 7. Three phase motors will also vibrate less and hence last longer than single phase motor of the same power used under the same conditions.
Large air conditioning, etc. Resistance heating loads such as electric boilers or space heating may be connected to three-phase systems. Electric lighting may also be similarly connected. These types of loads do not require the revolving magnetic field characteristic of three-phase motors but take advantage of the higher voltage and power level usually associated with three-phase distribution.
Fluorescent lighting systems also benefit from reduced flicker if adjacent fixtures are powered from different phases. Large rectifier systems may have three-phase inputs; the resulting DC current is easier to filter smooth than the output of a single-phase rectifier. Such rectifiers may be used for battery charging, electrolysis processes such as aluminum production, or for operation of DC motors. An interesting example of a three-phase load is the electric arc furnace used in steelmaking and in refining of ores.
In much of Europe stoves are designed for a three phase feed. Usually the individual heating units are connected between phase and neutral to allow for connection to a single phase supply. In many areas of Europe, single phase power is the only source available. Occasionally the advantages of three-phase motors make it worthwhile to convert single-phase power to three phase. Small customers, such as residential or farm properties may not have access to a three-phase supply, or may not want to pay for the extra cost of a three-phase service, but may still wish to use three-phase equipment.
Such converters may also allow the frequency to be varied allowing speed control. Some locomotives are moving to multi-phase motors driven by such systems even though the incoming supply to a locomotive is nearly always either DC or single phase AC.
Because single-phase power goes to zero at each moment that the voltage crosses zero but three-phase delivers power continuously, any such converter must have a way to store energy for the necessary fraction of a second. One method for using three-phase equipment on a single-phase supply is with a rotary phase converter, essentially a three-phase motor with special starting arrangements and power factor correction that produces balanced three-phase voltages.
When properly designed these rotary converters can allow satisfactory operation of three-phase equipment such as machine tools on a single phase supply.
In such a device, the energy storage is performed by the mechanical inertia flywheel effect of the rotating components. An external flywheel is sometimes found on one or both ends of the shaft. A second method that was popular in the s and 50s was a method that was called the "transformer method". In that time period capacitors were more expensive relative to transformers. So an autotransformer was used to apply more power through fewer capacitors. This method performs well and does have supporters, even today.
The usage of the name transformer method separated it from another common method, the static converter, as both methods have no moving parts, which separates them from the rotary converters. Another method often attempted is with a device referred to as a static phase converter. This method will not work when sensitive circuitry is involved such as CNC devices, or in induction and rectifier type loads.
Some devices are made which create an imitation three-phase from three-wire single phase supplies. Many three-phase devices will run on this configuration, but at lower efficiency. Variable-frequency drives also known as solid-state inverters are used to provide precise speed and torque control of three phase motors. Some models can be powered by a single phase supply. VFDs work by converting the supply voltage to DC and then converting the DC to a suitable three phase source for the motor.
Digital phase converters are a recent development in phase converter technology that utilizes software in a powerful microprocessor to control solid state power switching components.
This microprocessor, called a digital signal processor DSP , monitors the phase conversion process, continually adjusting the input and output modules of the converter to maintain balanced three-phase power under all load conditions. A polyphase system is means of distributing alternating current electrical power. Polyphase systems have three or more energized electrical conductors carrying alternating currents with a definite time offset between the voltage waves in each conductor.
Polyphase systems are particularly useful for transmitting power to electric motors. The most common example is the three-phase power system used for most industrial applications.
In the very early days of commercial electric power, some installations used two phase four-wire systems for motors. The chief advantage of these was that the winding configuration was the same as for a single-phase capacitor-start motor, and, by using a four-wire system, conceptually the phases were independent and easy to analyze with mathematical tools available at the time.
Two-phase systems have been replaced with three-phase systems. A two-phase supply with 90 degrees between phases can be derived from a three-phase system using a Scott-connected transformer. A polyphase system must provide a defined direction of phase rotation, so mirror image voltages do not count towards the phase order.
A 3-wire system with two phase conductors degrees apart is still only single phase. Such systems are sometimes described as split phase.
Polyphase power is particularly useful in AC motors, such as the induction motor, where it generates a rotating magnetic field. Nikola Tesla and Michail Dolivo-Dobrovolsky invented the first practical induction motors using a rotating magnetic field - previously all commercial motors were DC, with expensive commutators, high-maintenance brushes, and characteristics unsuitable for operation on an alternating current network.
Polyphase motors are simple to construct, are self-starting and have little vibrations. Higher phase numbers than three have been used. A common practice for rectifier installations and in HVDC converters is to provide six phases, with 60 degree phase spacing, to reduce harmonic generation in the AC supply system and to provide smoother direct current.
Wire and Cable Extrusion is a manufacturing process used to shape molten plastic. Different process still existing according to the different compounds requested by the market. The most used process is dedicated to the thermoplastic and thermosetting materials where an Internal machine barrel friction and an external heat supply by way of heat resistors are exploited to transform an infeed base material into a finished or semi-finished product, shaping material by forcing it through a die. By the way, another opposite process is available for rubber extrusion with many different vulcanization solutions engineered to heat the insulation after the die trough.
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Contact us for BIG Discounts on large orders. Three-phase electric power is a common method of electric power transmission. It is a type of polyphase system mainly used to power motors and many other devices. A three-phase system uses less conductor material to transmit electric power than equivalent single-phase , two-phase, or direct-current systems at the same voltage.
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Our low-voltage cable, medium-voltage cable and high-voltage cable products are purchased by many large power companies such as State Grid and Electric Power Company and highly recognized and evaluated by customers. At the same time we provide the best after-sales service. Offering flexibility. We have a large number of models, and our goal is to let the prisaman cable illuminate the way people go home and illuminate thousands of households. Whether enhancing power and control capabilities or enabling the optimal functioning of data and communication systems, our cable solutions successfully equip transport vehicles around the world, proving their value every day, even in highly demanding and highly specialised environments. Shijiazhuang Taihao Technology Co. Prisaman is our international brand name. We have nearly 35 years of experience in wire and cable production and sales, serving domestic and foreign companies and receiving high praise and recognition from customers. We are committed to serving every customer with the philosophy of connecting our cables to the world and illuminating the world. Our products sell well all over the world and the main reason is that we attach great importance to business honesty.
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Single-throw knife switches, molded-case switches, switches with butt contacts, and circuit breakers used as switches shall be connected so that the terminals supplying the load are deenergized when the switch is in the open position. However, blades and terminals supplying the load of a switch may be energized when the switch is in the open position where the switch is connected to circuits or equipment inherently capable of providing a backfeed source of power. If specified in paragraph j 4 of this section that one piece of equipment shall be "within sight of" another piece of equipment, the piece of equipment shall be visible and not more than By Standard Number
A power cable is an electrical cable , an assembly of one or more electrical conductors , usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed. The first power distribution system developed by Thomas Edison in in New York City used copper rods, wrapped in jute and placed in rigid pipes filled with a bituminous compound. Mass-impregnated paper-insulated medium voltage cables were commercially practical by During World War II several varieties of synthetic rubber and polyethylene insulation were applied to cables. Typical residential and office construction in North America has gone through several technologies:. Modern power cables come in a variety of sizes, materials, and types, each particularly adapted to its uses. Cables consist of three major components: conductors, insulation, protective jacket.
Why Power Cords Matter
These cables are used for flexible use for medium mechanical stresses with free movement without tensile stress or forced movements in dry, moist and wet rooms but not suitable for open air, as measuring and control cables in tool machines, conveyor belts, production lines in machinery production, in air-conditioning and in steel production. The earth core is laid in the outer layer. Selected PVC-compounds guarantee a good flexibility as well as an economic and fast installation. These cables are used for flexible use for medium mechanical stresses with free movement without tensile stress or forced movements in dry, moist and wet rooms and in open air. Must not be laid directly in soil or water. When screened for measurement, control and control line etc. Wiring cable for measuring and controlling purposes in tool machinery, conveyor belts and production lines, for plant installations, air conditioning and in steel production plants and rolling mills. Suitable for installation for flexible use for medium mechanical stresses with free movement without tensile stress or forced movements in dry, moist and wet rooms as well as outside fixed installation. Is not suitable to be used as direct burrial- or as underwater cable.
From non-metallic sheathed cable NM to high voltage aluminum cable Bartell provides manufactures with the equipment and technologies they need to bring consumers the highest quality, best performing cables. The Bartell high-speed tubular stranders are constructed with durability and efficiency in mind to meet the most demanding production requirements. With precise tension control and high linear speed this pay off systems is specifically suited to support the production of a variety of fiber optic cable configurations at the highest quality standards. Bartell cantilever units are known for their legendary performance. From its compact design to lower maintenance and improved flexibility they provide the dependability and performance our customers need. Our Roll Through styles are designed for fast and easy loading and unloading while being able to achieve a high-quality lay. With multiple features and smooth operation, these can be configured to meet any application. With the lift arms supported above the frame gantry style units provide a unique solution for large and hard to handle reels. From stationary to traversing these units provide a quality solution for complex production needs. Our standard caterpullers and capstans are available in a wide variety of designs, suitable for products up to 5 inches in diameter.
W-TEC cables provide universal connections
The Complete Guide To Stage Lighting Power Connectors & Plugs
Jacketing materials: standard, flame-retardant. Combined SZ stranding and jacketing for building wires, flexible power cords and power cables maximizes production. The Rosendahl RN-K SZ stranding and jacketing line offers optimized line configuration for various product mixes and materials.
Wire and Cable: Untangling Complex Environmental Issues
LQ Mechatronik-Systeme's W-TEC cables create a simple, continuous connection when used in mechanical and plant engineering, on building sites or for assembling units. These precisely assembled energy carriers are also essential elements of cable carriers and complete installation assemblies. A huge number of different energy and power cables are used in the market for electromechanical components and this results in the lack of clarity. However, there are considerable variations in quality.
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