Fossil fuels such as coal or oil are becoming increasingly depleted. According to the calculations of many experts, the current oil production rate cannot be increased much further, while the effects of climate change are becoming more and more evident. Therefore, we are not only forced to save energy, but also to produce energy in the best possible environmentally and climatically friendly manner.
Against the background of this increasingly clearly emerging scenario, the development and expansion of renewable energies has already been pursued for many years. FUHR is also following this global trend in the further development of its ultramodern rolling technology; be it hybrid drives, photovoltaics, wind or hydro power – our demanding customers have good reasons to rely on our innovative rolling mills for highly efficient energy generation concepts.
But also in the area of conventional energy resource exploitation, such as offshore technology, our rolling technology is leading in the production of flexible pipes for flow lines and jumpers.
Photovoltaic modules (PV modules) consist of several interconnected solar cells, which are combined with suitable materials into a sealed unit for protection against external influences like mechanical stress, weather conditions and corrosion.
PV modules consist of various components depending on the system: Crystalline modules are encapsulated with a front and rear module cover made of glass, acrylic or foil. The unit is sealed with liquid resin or with two foils under pressure and high temperature.
Since the voltage of a typical single silicon cell is, with 0.5 to 0.8 V, too low for technical applications, several solar cells are generally interconnected in a serial or parallel way.
The individual solar cells are connected into modules by means of so-called interconnect ribbons – thin, annealed and tinned copper ribbons which are soldered onto the cells, and whose low yield strength of about 50 N/mm² allows them to follow the thermally induced changes in length of the cells without damage.
At the edge of a PV module the interconnect ribbons are connected with flat copper bands of greater cross section – the so-called busbars – which serve as current collectors and transport the whole of the current produced to the rear side of the PV module.
The interconnect ribbons and busbars are referred to collectively as PV ribbons. Instead of cutting these ribbons of rolled broad copper strip with length cutting equipment, cold rolling technology is used in their production. The advantage lies in the effectively unlimited length and the homogeneous edges of the ribbons produced.
FUHR provides highly productive rolling mills for the rolling of interconnect ribbons and busbars from round copper wire. The rolled ribbons are formed into coils and can then be annealed and tinned in later processes. These processes sometimes take place in line with the rolling mill.
A wind power plant consists essentially of a rotor with a hub and rotor blades as well as a nacelle which contains the generator and often a gearbox. There are also systems with no gearbox. The rotating nacelle is mounted on a tower whose foundations provide the necessary stability. In addition, there is the monitoring, regulating and control system as well as the network connection technology.
In order to convert mechanical into electrical energy, three-phase asynchronous or synchronous generators are used. The generator is optimized for longevity, weight, size, maintenance requirement, cost and efficiency, where produces interactions between gearbox and network connection. The rotational speed of the generator can be constant, have two levels (for low and high wind speed) or be adjustable steplessly. For low rotational speeds, which occur with ungeared plant, synchronous generators are necessary.
To optimize the efficiency of the generator, square sections rather than round enamel insulated copper wires are finding increasingly frequent use today. Besides the better electrical efficiency, generators equipped in this way are characterized by a better power-to-weight ratio.
FUHR supplies rolling mills for rolling round copper wire into square. Thanks to the use of universal profile rolling apparatus which is typical of FUHR, especially high precision is achieved, which is necessary for the subsequent paint process.
CONTINOUSLY TRANSPOSED CONDUCTOR (CTC)
In the windings of electric motors, generators and transformers, copper wire with square sections rather than round sections is increasingly used today in order to boost the overall efficiency. The windings consist of a large number of individual wires which must be electrically insulated from one another. It is also important for the quality of the winding that the individual wires have the same length as far as possible.
Windings for high performance are normally wound by hand in view of the limited unit volume. In order to simplify this work and to reduce the chance of faults from different individual wire lengths, insulated-strand conductors were developed.
Several enameled insulated flat wires combined in special wiring machines to so-called insulated-strand conductors (see photo) and wrapped in paper to protect them from damage.
Insulated-strand conductors are often designated as CTC (Continuously Transposed Conductor).
FUHR supplies rolling mills for rolling round copper wire into square. By the use of universal profile rolling apparatus which is typical for FUHR, an especially high precision is achieved, which is necessary for the subsequent paint process.
FLEXIBLE PIPE ARMOURING
Without drilling rigs and ships, exploration and exploitation would be impossible on the high seas. Depending on the depth of the water, the oil and gas companies use various types for this: For exploration in shallow waters (up to around 60 meters) drilling rigs are suitable which stand on a flooded pontoon on the sea floor. For deeper water up to around 300 meters, drilling rigs with extensible legs are used (“jackup rig”): Once on location, the legs are sunk and dig themselves several meters into the seabed.
In still deeper waters it is no longer possible to position the drilling rig on the sea floor – instead it must float above the drill hole. These so-called “semi-submersibles” feature gigantic underwater ballast tanks ensuring that the drilling rig does not shift unduly, even in high seas. The position of semi-submersibles above the borehole is maintained by steel chains anchored to the sea floor. They can be used in waters up to 3500 meters deep. In such extreme conditions, drilling ships are also deployed that have no connection at all to the sea floor.
If an offshore deposit is ready for production, a production platform is installed above the borehole or the drilling rig is reconfigured as a production platform. After preprocessing, the raw material from the borehole is either transferred directly to land via a pipeline or loaded into tankers from the production platform.
Due to the great depth, the connection from the borehole to the water surface cannot be executed with rigid piping. Flexible hose lines are used instead. These flexible pipes are exposed to high stresses due to the water pressure. They are therefore designed for burst pressures of 500 bar and more. This is achieved by the use of a spiral pressure reinforcement profile (zeta, teta or C profile). The photo shows a zeta profile wire.
In order to take up the tension caused by the weight of the hose pipe itself, the profile wires of the pressure reinforcement are complemented by a tension reinforcement of a large number of flat wires.
FUHR supplies rolling mills for the production of both the flat wires for the tension reinforcement as well as the profile wires for the pressure reinforcement, from medium to high carbon steel wire in the cold rolling process. Because of the size of the profile cross section and the high stiffness of the steel grades used, here the largest cold rolling machines are used that are available on the market.
Characteristic for the classical direct current machines is a mechanical rectifier known as a commutator (polarity changer) that is mounted on the axis of the rotating machine. For motor operation, it serves as a polarity changer and produces an alternating current in the rotor which depends on the rotational speed.
In generator operation, it rectifies the alternating current from the rotor and produces a pulsating direct current. In some application scenarios, the direct current machine can be driven either as a motor or as a generator.
The rotor windings are connected via the commutator, which serves as a polarity reverser. Classical commutators include a sliding contact between the segments of the collector and two or more brushes. The sliding contacts are arranged so that they change the polarity of the rotor windings in such a way that current always flows through those windings that are moving at right-angles to the exciter field.
The brushes are made from a material which provides good contact with low friction (often self-lubricating graphite, sometimes mixed with copper powder).
FUHR rolling mills produce copper profile wires from which one piece (see photo) or multi piece commutators are produced.
Stranded (litz) wires exist in round or flat form, with or without enamel insulation, with various types of additional insulation, as well as braiding or taping. High frequency stranded wires consist of enamel insulated individual strands which are twisted together. They are used to compensate for the increase of conductor impedance at higher frequencies.
In an electrical conductor, the field of alternating current produces eddy currents which oppose the flow of current. These increase at higher frequencies. To the direct current resistance is added a frequency-dependent alternating current effective resistance. The eddy current losses are greatest in the middle of the conductor and reduce towards the edge. The majority of the current therefore flows on the surface of the conductor (skin effect). The expression penetration depth of current is also used.
With the proximity effect, the eddy current losses arise from the fields of neighboring conductors. In order to reduce these losses as far as possible, the conductor cross section is reduced (lower eddy current losses) and compensates by using several conductors in parallel. To compensate for the influence of the fields on the individual conductors, the conductors are twisted together (braided). The twisting must be selected so that the position of a wire, seen along the length of the braid, is in the center of the bundle as often as on the outer edge. HF braids should only be used up to about 2 MHz, since the influence of conductor capacitances becomes too great at higher frequencies.
Rectangular braids have the advantage over round braids of a higher packing density.
FUHR supplies rolling mills for reshaping round braids into rectangular braids. In order to ensure the greatest possible flexibility, these rolling mills use universal profile rolling equipment of type WST. This allows all square and rectangular dimensions to be produced without changing the rolls.
SPIRAL WIRE (BOWDEN CABLE HOUSING)
Bowden cable housings consist essentially of a flat wire helix and a plastic covering. An optional lining with a plastic tube significantly reduces the system’s internal friction and with the use of corresponding braids or cables the efficiency of the system is considerably increased.
For the production of the flat wire helix, round wire is cold rolled to the desired size and subsequently wound in a helix. The flat contact faces between the windings give the flat wire helix a high stiffness and a low compressibility in the longitudinal direction and make them suitable for precise guidance and high resistance to pressure, as is required for most actuation and transmission applications.
With FUHR rolling mills, round steel wire is rolled into rectangular profile wire. If these are used with FUHR type WST universal profile rolling equipment, then all dimensions of rectangular profiles can be produced without changing the rolls.
Trolley wire is one way of supplying power, along with the third rail. In railed transport (trams, surface and underground railways, mountain or cable railways) they supply the traction vehicle with current.
Special means of transport like trolley buses or electric ferry boats can obtain their electrical energy from them. A trolley wire consists of a copper profile wire which is hung at a constant height above the path of the vehicle.
The electric traction units have current collectors that are in contact with the overhead line. The electric circuit is completed by the rail as the return path. An additional conductive path is required for trolley buses and electric ferry boats.
With FUHR rolling mills, trolley wires are produced from pure or alloyed copper wire. Here, the first forming steps use a die to reduce the cross section and increase the strength. The profiling takes place in the next forming steps with profile rolling apparatuses.
Transformer or magnet wire is a copper wire which is coated with an insulating layer of enamel in its production. Compared with other insulation materials with the same effect, the thickness and the weight of this enamel insulation is very light. This wire is therefore preferred for the construction of electric coils, transformers and machines.
The use of enameled copper wire has beneficially reduced the mechanical size of electrical machines, where the concentration of the electric and magnetic fields in smaller spaces has resulted in even further space savings. This reduction in size ultimately leads to energy savings from shorter conductive paths for the same power output.
The classification of the enameled wires follows the International Electrotechnical Commission (IEC) standards 60317 and 60851. Wires are classified by temperature index (continuous running temperature), breakdown voltage and thermal shock behaviour.
In order to obtain smooth, concentric and nonporous films, enameled wire is usually painted and baked between 6 and 20 times. A rule of thumb says that the enamel film makes up about 10 % of the weight of the enameled copper wire. The resulting larger diameter is referred to as increase.
In the event of processing errors, electrical breakdown or as a result of continual pre-discharge in air spaces, the enamel layer can be damaged and a shorted coil occurs to neighboring wire layers. The insulating enamel will be still further damaged by heat arising from the resulting shorted coil, so that the number of shorted coils increases and the bare wires finally produce a short circuit.
In order to avoid this kind of shorted coil, it is essential to produce a copper wire with the lowest possible dimensional tolerances as input to the subsequent enameling process. This is the only way to achieve as constant an enamel thickness as possible over the entire cross section.
FUHR supplies rolling mills for rolling round copper wire into square wire. By the use of universal profile rolling apparatus which is typical for FUHR, an especially high precision is achieved, which is necessary for the subsequent paint process.