Definition and Criteria of Choice
Our company proposes, in cross section, various values of GMR, in order to minimize losses and optimize cable costs due to energy consumption and the reactance value.
We use advanced techniques to reactance calculations of the flexible circuit and power losses based on the furnace geometry and cable design.
The permissible current density is 4.5 Amps / mm2 for direct arc furnaces.
For ovens in which current variation is very small (reduction of metal alloys, for example), this current density may be 8 to 9 Amps / mm2.
Radius of curvature
The minimum radius of curvature of a cable should be approximately 6 times the inner diameter of the outer hose. A value less than this may lead to rapid deterioration of the outer hose, or block the passage of water refrigração.
Losses, reactance and GMR
In order to limit the power loss and voltage of the secondary circuits, GMR (Medium Ray Gométrico) of each stage should be maximum in most cases. If the number of cables per phase is given, there are two ways to molhorar the GMR:
-otimizando the radius of the Components;
-otimizando the distance between the cables of the same phase, and optimizing the distance between the phases.
Concentric Lay and Rope
General characteristics of cables W. Rady
Made of natural rubber, vulcanized and designed with resistance to pressure of 150 psi with a maximum electrical resistance of 50 MOhms the 1000Vcc. Its mechanical caracterísicas allow withstand harsh operating conditions: tensile and shear stresses due to the oven movements, internal and external mechanical shock due to electromagnetic stresses, radiant heat of the molten steel and molten metal splash (splash).
The cables are designed with electrolytic copper conductor, high electrical conductivity.
Concentric lay The driver consists of several layers of wire ropes.
The formation of each strand is calculated depending on the diameter, allowed the driver to maintain its circular shape whatever movements.
Rope Lay The driver consists of a helically arranged chordae layer surrounding the core.
It consists of a synthetic rubber hose or metal propeller designed to keep the ropes in the correct position.
For large cables, the core is connected to the terminal by means of a spring differential effect.
Differential effect of spring
This stainless steel made structure is intended to ensure the mechanical connection between terminals (hard) and the core (flexible). When the cable is subjected to severe forces (gradual curvature efforts) spring, the differential effect is anchored by welding to the terminal and the core by means of stainless steel clips.
In some situations it is not possible to use the differential effect of spring, a metal propeller is used.
stainless steel made no magnetic AISI 304 (to protect against Foucault currents).
Electrolytic copper ETP made machined, forged or rolled with high electrical conductivity. The dimensions of the terminals are designed to ensure a contact area that meets a density with minimum current of 0.7 A / mm2.
They are made with a highly abrasion resistant rubber and are designed to protect cables from impact and friction caused by the movement of the same, are sacrificial elements.
The request may be various other protections acrecentadas such as fiberglass sleeve with aluminum (antiradiation), glass fiber sleeve and synthetic aramid fiber (splash).
* On request we can provide:
high resistance to abrasion hose with stitched or cured coatings.
It is a new product developed by the engineers of our company in the field of flexible electrical connections in response to problems identified by usuáros. We know that at the opening of the furnace, the electrodes generate the arms around its vertical axis and receiving an intensity proportional to the twisting movement of the arms. Such a move would affect the outer hose and requires a great effort of the furnace structure.
Thanks to its functional and technical features, the rotating terminal allows:
-Reduced Downtime for maintenance thanks to the mounting ease.
-reduction Of mechanical stresses on the structure.
-Increase The life of the rubber hose (always above average thereof)
We can meet the needs of oven manufacturers (tambémdo type of arc) and its users to optimize the cable operating conditions without modifying the electrical-Features and flexibility of BWR cables. Tests conducted at our factory by appropriate instrumentation proved that the difference in torsional strength, flexible connection (jumper) between the two systems is 80%.
Since 1991, when the rotating terminal was launched, our customers are using this system successfully.
Other models on request.
Quick Mount Device – Quick coupling – Assembling