Ahead thanks to own technologies

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Serial production of material grade LE34 and brushes of it for turbine- and hydro-generators has been mastered

The brushes of material grade LE34 manufactured by Firm LEG ltd. have been tested and are successfully used at Zmiev thermal power plant (PJSC Tsentrenergo) in brush and contact joints of turbine-generators.
The material grade LE34 has run a full cycle of tests to demonstrate a long operational lifetime, unipolarity, stable operation at higher vibration of contact rings and complete absence of sparking.
In comparison with material grade ЭГ-4, which is generally unstable in high-power machines, LE34 grade shows a stable operation under more severe conditions.
The tests have shown, that LE34 material can not only substitute for ЭГ-4, but also enhance the service of turbine-generator brush and contact joint due to more stable rates.
The average wear of brushes grade LE34 in high-power electric machines (200-300 MWth) is 3,5 mm/1000 h, while the brush material grade LFC554 (recommended by manufacturer Mersen (former Carbon Lorraine) in exchange for ЭГ-4) has an average wear of 3,8-5,0 mm/1000 h at 80-160 MWth power (source http://inkommash-novosib.ru).

Technical specifications of brushes made of material grade LE34* and ЭГ-4**:

Brush grade
Specific electrical resistance, mkOhm•m
Voltage drop on a pair of brushes, V Coefficient of friction, max/average Wear at SCC installation, mm,
not more
Linear velocity, m/sec, not moreCurrent density, А/sm2,
not more
 Suggested specific pressure on a brush, kPa
LE34 from 6 to 16 from 2,0 to 3,6 0,19/0,11 0,50 80 20 from 15 to 25
ЭГ-4from 6 to 16from 0,8 to 2,00,25/н.д.0,6060 12from 15 to 25

Well-functioning production cycle allows Firm LEG ltd. to manufacture graphite electrical brushes of material grade LE34 in any design and number.
Application of electrical brushes LE34 with brush holders made by Firm LEG ltd. improves operational quality of rotor contact rings, prolongs their operational service and maintenance interval, reduces the influence of human factor on the quality of generator brush joint maintenance.

*Specifications according to technical conditions TУ У 27.9-14111810-006:2018
* Specifications according to technical conditions ТУ 16-88 ИЛЕА.685211.037ТУ

Date: 06.04.2020

Today Company LEG ltd. celebrates 27th anniversary of its foundation

Company LEG ltd. celebrates 27th Our congratulations to a friendly, united team of talented and high-experienced coworkers on this great day! We with you to progress and move forward and upward! Never stop at what you have achieved. Stability, reliability and сonfidence in the future!

Ahead thanks to own technologies!

Date: 01.04.2020

The positive results of works of the electric brushes were obtained with upgraded polymer overlays NK-8

polymer overlays NK-8Dumper rubberized overlays NK-8 had successfully tested on Zmiev HES. Undoubted effect were marked at reduction of vibrations in compared with metal overlays NK-1 and NK-2.

Date: 21.08.2018

Specialists of the Company "LEG" Ltd. have developed a brush holder with a roll constant-pressure spring

Brush holder with a roll constant-pressure spring

Specialists of the Company "LEG" Ltd. have developed a brush holder (see fig.) with a roll of constant-pressure, which helps to prolong the сommutator and the brush service life; excludes the «human factor»; allows to install a brush with a large radial size (up to 80 mm); provides a uniform constant pressure on the brush. The figure shows a brush with a shock-absorbing polymeric plate NK-8. The plate is unified and allows to install the brush both in a traditional brush holder, including the one with collet gripping unit, and in the brush holder with the roll constant-pressure spring.

There is a vertical groove in the brush box, which allows visual wear monitoring, and if there is a retainer on the plate NK-8 (in the figure), it limits the ultimate wear of the brush.

 

Date: 07.08.2018

A new type of overlays NК-8 is developed

Overlays NK-8A new type of overlays NК-8 is worked out and is undergoing tests now. In case of positive test results it is supposed to replace metallic overlays NК-1, NК-2 and rubber overlays NК-6, NК-7 with these ones at all types of carbon brushes execution.

Date: 20.07.2018