Telema SpA is an Italian company considered to be the European specialist in the field of electric power resistors. Now exclusively represented in South Africa by AGF Technology, Telema has since 1995 dedicated and focused its efforts on these products.
The Telema Group includes Resistel SA of France, TPR of the UK, and TBeS of the USA. With the majority owned by Telema, it has a total staff of 90 employees with a turnover in 2000 of US$15m. This result places the group amongst the first three leading companies in the field of electric power resistors in the world.
Telema's direct exports represent 50% of the company's production. The company says that to better capture local requirements and opportunities, as well as to offer a good service to its customers in other countries, saw the establishment of its subsidiaries Resistel, TPR and TBeS. In addition to this, it has also founded a number of European and Pan-European agreements with other companies. These agreements foresee the local design and assembly of resistors using active elements desiged in the home plant.
Constantly striving towards internationalisation the Group boasts some of the following leading companies as clients: ABB, GEC Alsthom, Siemens, Schneider, Ansaldo, Firema, Parizzi, ENEL, EDF, Nuclear Electric, National Grid, FS, SNCF, SNCB, DB, Brush, Snamprogetti, Shell, Rolls Royce etc.
During its 25 years of activity, the company has acquired considerable and specific competence in all applications of electric power resistors. Some products it offers are listed below.
* Resistors for railway applications: This range of power resistors covers all the applications in railway equipment, eg dynamic braking resistors, snubber resistors, filter charging/discharging resistors, crowbar resistors, di/dt resistors. Typical characteristics of a traction resistor are: minimum weight and bulk, high reliability, low operating temperature, high vibration resistance and high maintainability.
* Neutral earthing resistors: The best way to protect transformers and generators against ground fault currents is to install these between the star point and the earth. This resistor will limit the fault current to a pre-fixed value so as not to damage the unit leaving time for protection to be activated.
* Neutral grounding resistors: These range from class 3,6 to 72,5 kV with current at several thousand amperes and chassis protection from IP 23 to IP 55. These resistors can incorporate loadless switches, load-break switches, vacuum contactors, CT, VT, etc.
* Load resistors: Load resistors are custom-designed to optimise your testing capabilities. Made of low temperature-coefficient materials to exacting tolerances, they provide an accurate and stable load to minimise unwanted variables in testing. Telema resistor grids are made in thickness from 0,5 to 4 mm, and various configurations. They feature very low inductance, very high overload capabilities and long life. Suited to either convection or forced-air cooling, they allow flexibility in tailoring one's load bank precisely to requirements.
* Starting and braking resistors: Telema manufactures rugged, stainless steel resistors designed for trouble-free service. They are in service on cranes and heavy industrial drives, they are employed in applications: wound rotor motor control; reverse braking (plugging resistors); primary starting resistors; braking for inverter drives.
* Harmonic filter resistors: The increasing use of solid-state devices in power system converters, motor controls etc has created the problem of harmonic distortion. RC circuit filters are used to remove harmonics but can be difficult to tune. Resistors are often used to increase bandwidth. Element design minimises both skin effect and reactance; outdoor stainless steel enclosure as standard equipment; custom enclosure and finishes available; protection from IP23 (standard) to IP55.
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