WHY CARBON ?
Carbon has unique self lubricating properties that enable machines to run for thousands of hours with little commutator wear. In addition to this unique mechanical advantage, carbon has a relatively high contact resistance which enables motors to operate sparklessly over a wide range of currents and speeds. Carbon has yet another advantage which enables it to withstand bad operating conditions - it cannot melt. This means there is no danger of fusing or welding to adjacent metal parts should very severe sparking or a flashover occur. Naturally with so many sources of raw materials available, very many mixtures of carbon can be made which, with variations in subsequent treatments, make it possible to give the final products a whole range of characteristics to suit the widely varying requirements of different machines. These advantages that carbon offer for brush material are so very important that it is virtually the only element best suited for such an application.
Hatim Carbon manufactures all types of carbon brushes. We take special care in the manufacture of every brush to
ensure supply of the exact material required both in the grade and dimensional accuracy.
To meet successfully the many and varied applications for brushes on all types of electrical machines, and to render a complete and satisfactory service to the user, a large amount of brush grades are carried in stock by us. In some cases, peculiarities of machines or operating conditions call for special consideration in selecting a suitable grade. We suggest the recommended applications for these grades based on the combined experience of our engineers and a vast amount of data accumulated in the field.
We believe that every component of the brush is integral to the current conduction process, and ensure the highest standards of accessories are used. Our core values are two fold:
Maximized Brush Life & Lower Wear
Decreased downtime of the Motor
Being one of the exclusive members of the E-Carbon group, Hatim Carbon represents numerous international brands and has access to various electro graphite, natural graphite and metal graphite grades as produced by major international grade manufacturers.
With the supply of carbon raw materials also comes the 100% committed technical support from our suppliers with regards to grade selection, troubleshooting, manufacturing techniques and carbon brush manufacturing equipment.
GRADE SELECTION & PRODUCTION
The carbon brushes used on electrical equipment have two distinct functions. First, they must carry the load current into and away from the rotating element of the machine. Second, on commutating machines, the brushes must control within safe limits the short-circuit current that results from uncompensated voltage in coils that are short-circuited by the brush during the interval of commutation. In this capacity, the brush should slide smoothly at surface speeds that are often considerably in excess of 100 miles an hour.
This is obviously quite an assignment. In addition to the need for good electrical conductivity, heavy demands are placed on the lubricating, thermal, and refractory properties of the brush material. No material other than carbon is capable of meeting these exacting requirements. The optimum combination of these characteristics that is best suited to one application may not be best for another. The many factors that influence brush performance must be considered in making the proper selection of a brush grade for a particular application
These are made from lamp black and/or petroleum coke and /or artificial graphite previously ground, selected and agglomerated with pitches or coal tars of well defined compositions.
The powders thus moistened are compressed and plates thus obtained are fired to about 1, 100°C.
Brushes are hard and give a polishing action and have a medium value contact drop
Old slow machines with or without interpoles and generally at low voltage. With or without flush mica.
LIMIT OF APPLICATION
Current Density 6-8 A/cm²
Peripheral Speed-about 25 m/s.
Prepared in the same way as amorphous and then subjected to a thermal treatment at high temperature (above 2,000 C) in order to transform the basic amorphous carbon into artificial graphite
Brushes have average contact drop and low or average friction, have reduced losses and are particularly adapted to high speed applications
For all modern machines whether stationary or for traction, high speeds, low, medium and high voltage and constant or variable loads.
LIMIT OF APPLICATION
Brush current densities:
8 to 12 A/cm² under steady conditions 20 to 25 A/cm² for short duration peaks.
Peripheral Speed: Up to 60 m/s
Manufacture is equivalent to that of metals grades to handle the most demanding requirements in critical applications.
High conductivity/Low resistivity, Accurate signal/power/data transfer, Good thermal performance, Oxidation & chemical resistance, Low wear rate, increasing contact life, Low coefficient of friction, Non-welding
Contacts, Transmission of testing currents, micro motors of low voltage tachometers, Tachogenerators, measuring purposes, ships earthing applications.
The base constituent is purified natural graphite or previ ously ground artificial graphite, mixed with other con stituents in well defined quantities, agglomerated with appropriate binders and fired at around 1,100°C.
A soft plastic brush having very good resistance to shock and mechanical vibration, and generally with good cleaning properties
Steel rings for high speed asynchronous or synchronous machines.
LIMIT OF APPLICATION
Brush current density: 10 A/cm². Peripheral Speed: 75 m/s.
These blocks are made by mixing in suitable proportions purified natural graphite and copper in powder form with the addition of powders of lead and/or tin. Equally a part of the metal graphite group are those brushes which are impregnated under pressure with pure molten copper or a mixture of molten copper and lead
Dense or very dense Brushes with low friction and very low contact drop therefore loading to very low losses.
DC machines of slow speed and low or very low voltage: Bronze rings of slow speed asynchronous motors, heavily loaded, with or without brush lifting gear. Bronze or steel rings of synchronous motors of low or medium speed
LIMITS OF APPLICATION
Brush current density: 12-30 A/cm² continuous of the order of 100A/cm instantaneous transient peaks Peripheral Speed: Up to 35 m/s.
Natural or artificial graphite with or without additions is ground agglomerated with a thermo-hardening resin of the bakelite type. The mixture is compressed and polymerized at a suitable temperature.
Brushes are of high mechanical and electrical resistance, good commutating properties, clean running with high contact drop and therefore high losses.
AC commutator motors of the Schrage or Schorch type. Many DC machines for traction or stationary of medium speed and load.
LIMIT OF APPLICATION
Brush current density: 10 A/cm² continuous. Peripheral Speed: Up to 40 m/s.
Hatim Carbon maintains extensive stocks of all grades (Indian & Foreign) to correctly choose their grades for the specified application. Our careful selection of grades enable us to better assist our customers and ultimately better the quality of our product.
All the Flexibles are of the highest grade annealed, stranded electrolytic copper wire. Wires in various gauges are used to ensure good flexibility. Special care is taken during fixing process not to allow blemishing or oxidation.
Each and every brush piece is sized and checked to conform to the tolerances permitted by B.S.S. 96 of 1954 (+.000"-.003" for breadth and thickness). All surfaces are plane and smooth and at the specified angles to each other. All chamfers, curvatures, slots, notches, shoulders, grooves etc., are made on the latest machines with special jigs and fixtures to ensure accuracy and uniformity. No broken edges or damaged corners or pittings will be found in our brushes. Brushes are checked by trained inspectors at each and every stage of production.
Connections are formed either through tamping or rivetting. The drill holes are made and shaped in automatic machines with specially made drills and tools. The pulling strength of the shunt are regularly tested during production as per NEMA Standard. Tamped connections are overlooked by our most expeirenced worksmen ensuring a firm connection.
Insulations are provided with proper consideration to the requirement of the machine, it's location and duty. They are rated for toughness, electrical insulation, resistance to heat, moisture and corrosive atmosphere.
Hatim Carbon terminals are also made from specified material in our own Accessories Department. They are properly fixed on the shunts by means of dies to ensure an unfailable grip and are soldered to the flexible permanently. Special process is adopted for soldering to avoid the solder coming on the flexible or corrosion of the flexible by the effect of Flux, a condition generally encountered in ordinary soldering.