How to Select Carbon Brushes for Motors 1 and Generators

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have use as contacts and as a base for metal impregnated Contents grades.

Page Electrographitic Brushes Grade Selection

...... Brush Grade Families 1 Electrographitic brushes are baked at temperatures in Grade Characteristic Definitions ...... 3 excess of 2400°C that changes the material physically to a more graphitic structure. Apparent density, strength, Special Brush Types hardness, and resistivity can be closely controlled through Laminated Brushes ...... 5 raw material composition and processing to achieve Fluted Brushes ...... 5 . superior commutating ability while providing long life. Pre-Radius Brushes ...... 6 . The high processing temperature volatizes impurities which Rubber Hardtop Brushes ...... 6 6 makes electrographitic brushes generally free from Surface Cleaning Brushes ...... abrasive ash. Therefore, commutators must have undercut Surface Rounding Brushes ...... 6. mica since very little mechanical wear results.

Electrographitic materials in general are fairly porous which permits treatment with various organic resins or inorganic Engineered Brush Grades materials. The treatments increase strength and lubricating Electrographitic ...... 6. ability which generally increases brush life significantly at Graphite ...... 9 high operating temperatures and at lower humidity. Metal Graphite ...... 10. Treatments can also permit electrographitic materials to operate satisfactorily in a variety of contaminated atmospheric environments.

Brush Request Form ...... 11 . 12 Friction characteristics with electrographitic materials can Grade Matrix ...... be controlled through raw material combinations before graphitization and also by treating the finished product with organic resins. Brush face temperature is a primary influence in determining the coefficient of friction as shown by the typical curve of coefficient of friction vs. temp chart.

Brush Grades Families Typical Coefficient of Friction vs Temperature Brush grades are usually classified according to the 0.40 manufacturing processes and the types of carbons and other ingredients used. The four main brush 0.30 grade families are: 0.20 Carbon Graphites Electrographites 0.10 Graphites CoefficientofFriction Metal Graphites 80 100 120 140 160 180 Brush Temperature - Degrees C Carbon Graphite Brushes Figure 1 Carbon graphite brushes made their entrance early in the brush industry. They are high-strength materials with a pronounced cleaning action. Carbon graphite brushes are Electrographitic brushes are generally capable of generally limited to lower current densities 45 amps/in² continuous operation at 80 amps/in² (12.4 amps/cm2) and 2 (7 amps/cm ) and are used on older, slower speed surface speed of 7000 feet/minute (35.6 m/sec). machines that reach maximum surface speeds of Intermittent operation at higher values is not uncommon. approximately 4000 feet/minute (20.3 m/sec). The high They are widely used in the industrial, transportation, friction generated with this type of material also makes it mining and aerospace industries on both AC and DC unattractive for present day use on commutators, but does machinery.

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1

Grade Characteristic Definitions

Graphite Brushes The characteristics of the most widely used brush grades Graphite brushes are composed of natural or artificial are shown in the tables on pages 6 - 10. The following graphite bonded with resin or pitch to form a layered brush definitions and explanations will help you to interpret these material. Natural graphite usually contains ash which gives tables. the brushes an abrasive or cleaning action. Artificial graphite generally does not contain ash nor does it have the Specific Resistance flaky structure of natural graphite. Unless otherwise specified, specific resistance (or Graphite brushes are characterized by their controlled resistivity) in ohm-inches (micro ohm-meters) is equal to the filming and excellent riding qualities on both commutators resistance that a specific volume of brush material offers to and slip rings at brush current densities 45 to 65 amps/in² the passage of current. Specific resistance is measured in (7 to 10 amps/cm2). They are not capable of sustained the length direction of the brush, since resistance in the operation at higher current densities like electrographitic direction of width or thickness may be considerably materials; however, higher surface speeds are often different. Specific resistance is calculated from permitted with some type of graphite materials. measurements on a test sample as follows:

The fast filming properties of graphite brushes is very R = (E x W x T) / (I x L) (English) beneficial in protecting the commutator or slip ring during operation in contaminated atmospheres such as those seen R = (E x W x T x 10-3) / (I x L) (Metric) in paper mills. Their low porosity and higher density are Where R = the specific resistance in ohm-inches valuable in reducing commutator threading often (micro ohm-meters) encountered in contaminated environments.

E = voltage drop over length “L” Metal Graphite Brushes I = amps of current passed through the sample Metal graphite brushes are generally made from natural W = width of sample in inches (millimeters) graphite and fine metal powders. Copper is the most common metallic constituent, but silver, tin, lead and other T = thickness on sample in inches (millimeters) metals are sometimes used. L = that portion of the length, in inches

(millimeters), over which the voltage Metal graphites are ideal for a variety of applications drop “E” is measured because of their low resistivity. Metal graphites are used on commutators of plating generators where low voltage and high brush current densities are encountered. They operate on rings of wound rotor induction motors where high brush current densities are also common. Metal graphites are used for grounding brushes because of their low contact Apparent Density drop. For a brush material, the apparent density (also known as The following table describes some general applications bulk density) is equivalent to its weight in grams divided by where metal graphite brushes are used. its volume in cubic centimeters. Density must be considered Metal jointly with other brush characteristics in estimating brush Content Application quality. (Percent) Forklift and battery truck motors rated 24 – 72 Abrasiveness volts

Battery charging and welding generators The ability of the brush to prevent excessive build up of film 50% or Less rated 24 – 72 volts usually caused by corrosive or oily atmospheres is called the abrasiveness or “polishing action”. The abrasiveness of Slip rings at brush current densities 100 amps/in2 (15.5 amps/cm2) or less a brush may be influenced by its hardness, grain structure Plating generators rated 6 – 24 volts and ash content. The brushes are classified according to

65 to 85% abrasiveness as follows: “Low” indicates very little Slip rings at brush current densities less than abrasiveness (commonly referred to as “non-abrasive” by 125 amps/in2 (19.4 amps/cm2) the trade), “Medium” indicates some polishing action, “High” DC machines rated less than 6 volts. indicates pronounced polishing action which is usually 75% and Slip rings at brush current densities 150 obtained by using a material with high ash content or by the Above amps/in2 (23.3 amps/cm2) or less addition of a polishing agent. Grounding brushes

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Contact Drop Maximum Speed

Contact voltage drop for the brushes listed in this brochure The highest peripheral or surface speed in feet per minute are approximate values only and represent the total voltage (meters per second) recommended for the collector or drop (positive plus negative) obtained on a copper ring at commutator on which the brush is to ride is referred to as 50 amps/in2 (7.75 amps/cm2) while rotating at 2500 f/m the maximum speed. The maximum speed depends not (12.7 m/sec). only upon the characteristics of the brush material, but also upon the spring force, current density, type of brush holder, They are classified as follows: brush angle, condition of the ring or commutator, atmospheric conditions, etc. Consequently, the maximum Contact Drop Volts speed, conventionally listed as a brush characteristic, is Very High 1.7 and above only an approximation. High 1.2 to 1.7 Medium 0.6 to 1.2 Friction Coefficients Low Below 0.6 Brush friction is influenced by many variables including Current Carrying Capacity brush temperature, spring force, current, atmospheric conditions, mechanical conditions, ring or commutator The actual current carrying capacity of a brush is widely materials, surface films, speed and other factors. The slip influenced by operating conditions such as type of ring/commutator surface even under favorable conditions is ventilation, continuous or intermittent duty, speed and other continually undergoing changes caused by oxidation, factors. The brush grade current ratings are conservative, abrasion and moisture. some allowance having been made for overloads. Brushes have been run at currents considerably above those listed Friction chatter, noise and associated brush wear can be in the grades table. Metal graphites, for example, have accelerated with certain brush holder configurations. This is been operated at 180 amps/in² (27.9 amps/cm2) on certain especially true under conditions of light loads and lower high current generators. Electrographitic brushes have brush temperatures when the coefficient of friction is been operated at 100 amps/in² (15.5 amps/cm2) on similar relatively high (refer to Fig. 1). Specific brush grades are equipment with reasonably good results. used to lessen the severity of friction chatter under these conditions. Friction between the brush and rotating surface The current carrying capacity of a brush depends on the can be a major source of heat generation that causes operating temperature. On well ventilated machines, having serious temperature related problems. Commutators can small brushes, with large surface area in proportion to their distort, slip rings can move, and brush wear can become volume, and where brushes cover only a small percentage excessive when the coefficient of friction becomes too high. of the commutator or ring surface, conventional current densities can usually be doubled for short periods without The brushes are classified as follows: seriously jeopardizing the performance. However, increasing current density without making provisions for Friction Friction maintaining a low brush temperature may severely reduce Classification Coefficient brush life. The brush current density of a given machine can High 0.40 and above be calculated as follows: Medium 0.22 to 0.40 Low Below 0.22

D = I / (½ N x W x T) * for commutator machines

D = I / (N x W x T) * for slip rings Transverse Strength

D = brush current density in amps/in² The standard sample is supported near the ends on two (amps/cm2) knife edges as shown in Figure 2. A third knife edge I = total current in amps* presses on the top of the sample midway below the two *Armature amps for commutator machines supporting edges. The force is increased on the top knife *Rotor or secondary amps for slip ring machines edge until the sample breaks. The transverse strength is computed by using the beam formula, also called 3 Point N = total number of brushes on a commutator Method: or the number of brushes on an individual ring

W = width of the brush in inches (cm)

T = thickness of the brush in inches (cm)

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St = 3 x P x L / ( 2 x W x T²) Brush Description and Application 2 St = transverse strength in PSI (Kgf/cm ) Grade Recommended for:

P = the total force in pounds (Kgf) applied at the A good commutating grade with slight polishing upper knife edge L932 action operational range is 50 to 75 APSI (7.75 APSC to 11.6 APSC). L = distance between supports in inches (cm) L944 Treated grade fir improved life.

A good commutating grade with slight polishing W = width of sample in inches (cm) L963 action, also treated for low humidity protection. T = thickness of sample in inches (cm) L964 Stronger base material for improved life.

Similar to L932, provides improved filming vs. L966 L932.

Low friction base material, with slight polishing L983 action used in stubbing/leading (brush holder) configurations.

Table I

The second laminated style brush is a composite assembly of two or more grades of electrographitic materials that are of varying resistance. These brushes improve commutation, reduce commutator temperatures, and reduce commutator erosion.

Reduction of the resistivity of the various parts will reduce Details of transverse strength test the commutating ability slightly, but will increase brush life. Therefore, several combinations are listed in table II. Other Figure 2 variations in material can be made on request. Contact the Morgan AM&T Application Engineering team for assistance.

Special Brush Types Brush Grade Description and Laminated Brushes Application A high commutating There are times when a laminated design brush is desired. L351 brush with low (contact) The laminated “L” series has been developed to help the drop. Stronger base material designer and ultimate user to obtain more effective L352 performance from his commutator-type machine (where for improved life. conditions warrant a laminated brush). Similar to L352 but lower L357 friction. Less subject to There are two types of laminated brushes. The first chatter laminated style brush is a composite assembly of two or more grades of electrographite/graphite materials that Table II provide a slight polishing action to combat contaminated environments. These brushes improve commutation, reduce commutator wear and provide better brush life, Fluted Brushes where contamination is a concern. Brief application descriptions are listed in Table I. Many larger machines in operation are equipped with a fluted brush face to reduce the running time necessary to get a good brush fit and commutator film.

When replacement brushes are installed a few at a time, the fluted brush does not have to be sanded in. Using a fluted brush for replacements will decrease the possibility of damaging or stripping the commutator film surface when brushes are replaced and not sanded to fit the commutator 4 5

surface. On critical threading conditions, it is recommended Surface Cleaning Brushes that fluted brushes be used, as the brush allows for a quick brush fit and a more even film. The surface cleaning brush (SCB) is a preventative maintenance tool designed to give the best possible It is not necessary to remove the brush after the fluted performance in rotating equipment exposed to severe portion is worn away, but can be operated to the normal contamination. The SCB fits in the brush holder of the minimum wear length. motor or generator and cleans the commutator and/or collector ring during operation. The SCB does not limit the Pre-Radius Brushes apparatus output. For less aggressive cleaning, please refer to the laminated grades listed previously. For more An alternate method to form the brush to the surface of the information on SCB’s, refer to the technical data sheet on commutator is to machine a radius (pre-radius) in the brush Surface Cleaning Brushes. face. This machining applies a radius that is equal to or slightly larger than the commutator. Adding a pre-radius Surface Rounding Brushes does not remove the need to sand in a brush, but it does significantly decreases the time needed to match the The surface rounding brush (SRB) is another preventative contact surface. maintenance tool designed to give the best possible performance in rotating equipment (that has a rough riding Rubber Hardtop Brushes surface). The SRB fits in the brush holder of the motor or generator and smooths the commutator and/or collector Morgan AM&T manufactures a full line of rubber hardtop ring to a specific roundness as the machine operates. The brushes, also known as pads, designed to soften the impact SRB does not limit the apparatus output since it is made of from a rough commutator, giving longer brush life and the material compatible with the other brushes. SRB’s will reducing brush breakage. However, rubber hard top remove metal as they slowly grind off the high areas. For brushes are not a “cure-all” solution. For more information more information on SRB’s, refer to the technical data sheet on rubber hard top brushes, refer to the technical data on Surface Rounding Brushes. sheet on Rubber Hardtop Brush Applications.

Engineered Brush Grades

surface. Electrographitic On critical threading conditions, it is recommended Surface Cleaning Brushes

that fluted brushes be used, as the brush allows for a quick brush fit and aSpec. more even film. Trans. SurfaceThe Normal surface cleaning brush (SCB) is a preventative Res. Strength Con- Speedmaintenance Current tool designedDescription to giveand Application the best possible ItBrush is not necessaryΩ-in. to Dens. remove thelbf/in² brush aftertact the Fric- fluted ft/minperformance Density in rotating equipment exposed to severe portionGrade is worn(µΩ -m) away, butg/cm³ can be(kgf/cm²) operated Drop to the normaltion (m/sec)contamination. A/in² The SCB fits in the brush holder of the minimum wear length. motor(A/cm²) or generator Recommended and cleans for: the commutator and/or 0.0020 3700 6000 80 A variety of industrial and FHP machines. 234 1.48 VH L collector ring during operation. The SCB does not limit the Pre-Radius Brushes(51) (260) (30) apparatus(12.5) output.Good For general less purpose aggressive grade. cleaning, please refer to the laminatedCopper alloy grades slip listed rings previously.with current Fordensity more 0.00075 2700 6000 80 up to 75 APSI and speeds up to 6000 An258 alternate method to form1.60 the brush to the surfaceH of Lthe information on SCB’s, refer to the technical data sheet on commutator is(19) to machine a radius (191)(pre-radius) in the brush (30) Surface(12.5) Cleaning ft/min. Brushes. Also used on lightly loaded face. This machining applies a radius that is equal to or machines. 0.0030 1700 8000 80 Where excellent commutating ability is of slightly561 larger than the commutator.1.54 Adding VH a pre-radius M Surface Rounding Brushes does not remove(76) the need to sand(120) in a brush, but it does (41) (12.5) primary importance. 0.0029 Contaminated atmospheres where slight significantly decreases the time 1600 needed to match the 8000 The surface80 rounding brush (SRB) is another preventative 569 (74) 1.53 VH M polishing action is necessary. contact surface. (113) (41) maintenance(12.5) tool designed to give the best possible performance in rotating equipment (that has a rough riding 0.0027 2400 7000 80 Industrial and transit applications. Rubber571 Hardtop Brushes1.57 VH M surface). The SRB fits in the brush holder of the motor or (66) (169) (36) generator(12.5) and smooths the commutator and/or collector 0.0022 3200 6000 80 Mill-type motors and generators where Morgan581 AM&T manufactures1.61 a full line of rubberVH hardtop M ring to a specific roundness as the machine operates. The brushes, also known(56) as pads, designed(225) to soften the impact (30) SRB does(12.5) not limitnormal the commutationapparatus output is needed. since it is made of 0.0024 3700 6000 80 Where high strength and superior from590 a rough commutator,1.62 giving longer brushVH life M and the material compatible with the other brushes. SRB’s will reducing brush(61) breakage. However,(260) rubber hard top (30) remove(12.5) metal ascommutating they slowly ability grind is off needed. the high areas. For 0.0020 4000 6000 80 Where severe mechanical conditions brushes591 are not a “cure-all”1.66 solution. For moreVH information M more information on SRB’s, refer to the technical data sheet on rubber hard(51) top brushes, refer(282) to the technical data (30) on Surface(12.5) Rounding require Brushes. a high strength grade.. 0.0026 1400 8000 80 Where humidity is low or where filming sheetA451 on Rubber Hardtop1.50 Brush Applications. VH L (66) (99) (41) (12.5) conditions are difficult.

5 Engineered Brush Grades

Electrographitic

Spec. Trans. Surface Normal Res. Strength Con- Speed Current Description and Application Brush Ω-in. Dens. lbf/in² tact Fric- ft/min Density Grade (µΩ-m) g/cm³ (kgf/cm²) Drop tion (m/sec) A/in² (A/cm²) Recommended for: 0.0020 3700 6000 80 A variety of industrial and FHP machines. 234 1.48 VH L (51) (260) (30) (12.5) Good general purpose grade. Copper alloy slip rings with current density 0.00075 2700 6000 80 up to 75 APSI and speeds up to 6000 258 1.60 H L (19) (191) (30) (12.5) ft/min. Also used on lightly loaded machines. 0.0030 1700 8000 80 Where excellent commutating ability is of 561 1.54 VH M (76) (120) (41) (12.5) primary importance. 0.0029 Contaminated atmospheres where slight 1600 8000 80 569 (74) 1.53 VH M polishing action is necessary. (113) (41) (12.5)

0.0027 2400 7000 80 Industrial and transit applications. 571 1.57 VH M (66) (169) (36) (12.5) 0.0022 3200 6000 80 Mill-type motors and generators where 581 1.61 VH M (56) (225) (30) (12.5) normal commutation is needed. 0.0024 3700 6000 80 Where high strength and superior 590 1.62 VH M (61) (260) (30) (12.5) commutating ability is needed. 0.0020 4000 6000 80 Where severe mechanical conditions 591 1.66 VH M (51) (282) (30) (12.5) require a high strength grade.. 0.0026 1400 8000 80 Where humidity is low or where filming A451 1.50 VH L (66) (99) (41) (12.5) conditions are difficult. 5 6

Electrographitic (continued)

Spec. Trans. Surface Normal Res. Strength Con- Speed Current Description and Application Brush Ω-in. Dens. lbf/in² tact Fric- ft/min Density Grade (µΩ-m) g/cm³ (kgf/cm²) Drop tion (m/sec) A/in² (A/cm²) Recommended for: Steel or bronze field rings of 0.0004 3000 4000 80 synchronous motors and wound rotor AY 1.68 H M (10) (211) (20) (12.5) motor rings up to 100 APSI and up to 4000 ft/min. 0.0008 3700 6000 80 Low voltage battery lift trucks where low B344 1.65 H M (20) (260) (30) (12.5) contact drop is required. 0.0005 4200 5000 80 Steel and cast iron slip rings. D 1.65 H M (18) (296) (25) (12.5) Smaller diesel-electric locomotive main 0.0021 3700 8000 80 DE2 1.64 VH L generators and auxiliary equipment (53) (260) (41) (12.5) motors and generators. Traction and hoist motors operating 0.0025 4200 10000 80 DE25 1.69 VH L under severe conditions of temperature (64) (359) (51) (12.5) and low humidity. 0.0020 4500 8000 80 Transit traction motors. DE3 1.62 VH L (51) (317) (41) (12.5) Traction motors and wheel motors in off 0.0025 4400 10000 80 highway vehicles where high loads and DE7 1.67 VH L (58) (310) (51) (12.5) low humidity are present. Also suitable for motors in transit applications. 0.0020 5500 10000 80 Diesel-electric traction motors providing DE7000 1.67 VH L (51) (387) (51) (12.5) good commutation and long life. Larger diesel-electric locomotive main 0.0020 5000 8000 80 DE8 1.70 VH L generators, and other auxiliary (51) (352) (41) (12.5) equipment motors and exciters. 0.0013 4000 6000 70 Brass collector rings, also used for DE869 1.71 H M (36) (282) (30) (11) medium commutating service. 0.0020 5500 10000 80 High speed locomotive traction motor DE9000 1.68 VH L (51) (387) (51) (12.5) applications. 0.0035 2800 7000 70 Applications where friction chatter is F799 1.65 VH M (76) (197) (36) (11) encountered. 0.0013 3300 6000 70 Medium-duty commutating service. G 1.65 VH M (36) (232) (30) (11) Medium to low current density 0.0025 2800 8000 75 N19 1.61 VH L applications with normal commutation (58) (197) (41) (12) requirements. Industrial generators and exciters 0.0020 5000 8000 80 where long life is necessary . N38 1.70 VH L (51) (352) (41) (12.5) Exceptional ability to maintain film under lightly loaded conditions. 0.00075 4700 10000 80 Slip rings where a stabilized film is N39 1.77 VH L (19) (331) (51) (12.5) critical and long life is necessary. High commutating applications from 0.0024 1500 10000 80 N44 1.50 VH L large heavy duty motors and generators (61) (106) (51) (12.5) to less critical applications. Where excellent commutation is 0.0028 2000 10000 80 N48 1.58 VH L required and sustained high loads are (71) (141) (51) (12.5) present. Low or variable humidity conditions and where long periods of light loading are 0.0026 2800 8000 80 N6000 1.55 VH L a factor. Slight polishing action, also (66) (197) (41) (12.5) controls film in heavily loaded applications. 6 7

Electrographitic (continued)

Spec. Trans. Surface Normal Res. Strength Con- Speed Current Brush Ω-in. Dens. lbf/in² tact Fric- ft/min Density Description and Application Grade (µΩ-m) g/cm³ (kgf/cm²) Drop tion (m/sec) A/in² (A/cm²) Recommended for: Where a slight polishing action may be 0.0026 2800 8000 80 N66 1.62 VH L required for controlling commutator bar (66) (197) (41) (12.5) marking or other contaminants. 0.0021 3400 8000 80 Low/variable humidity conditions and where N964 1.60 VH M (53) (239) (41) (12.5) long periods of light loading are a factor. Slip rings of wound rotor or synchronous 0.0004 3000 4000 80 R20X1 1.70 H M machines used in low humidity or difficult (10) (211) (20) (12.5) filming conditions. 0.0021 2400 8000 80 Where intermediate commutating ability is SA35 1.54 VH L (53) (169) (41) (12.5) required. Where excellent commutating ability is 0.0026 1450 10000 80 SA45 1.49 VH L required. Used widely on industrial motors (66) (102) (51) (12.5) and generators. Where severe operating conditions such as 0.0026 1525 8000 80 transient overloads and improper machine SA4542 1.51 VH M (66) (107) (41) (12.5) adjustment are present and a slight polishing action is needed. Applications where SA45 would normally be 0.0025 1500 8000 80 SA4548 1.50 VH L used but where increased filming ability is (64) (106) (41) (12.5) required. 0.0028 1000 10000 80 Machines where superior commutation is the SA50 1.49 VH L (71) (70) (51) (12.5) primary requirement. 0.0008 4000 7000 80 24 to 80 volt DC machines where low T300 1.72 H M (20) (282) (36) (12.5) humidity and high loads are present. Where excellent commutating and riding 0.0030 2700 8000 80 properties are required. Applied on high- T416 1.62 VH M (76) (190) (41) (12.5) voltage machines used in steel mills, paper mills, dragline generators, etc. 0.0030 2000 8000 80 Heavily loaded, difficult to commutate T500 1.57 VH M (76) (141) (41) (12.5) machines. Long life at lower humidity. 0.0022 4300 8000 80 General industrial and transportation T508 1.68 VH M (56) (303) (41) (12.5) applications. 0.0029 3900 8000 80 The plastics industry where good filming and T550 1.63 VH M (74) (275) (41) (12.5) excellent commutation is necessary. 0.0030 2400 8000 80 Wide variety of industrial applications where T563 1.58 VH M (76) (169) (41) (12.5) excellent commutation is necessary. 0.0030 2500 8000 70 Contaminated atmospheres seen in paper T566 1.62 VH M (76) (176) (41) (11) mills and where load requirements are high. 0.0027 3100 7000 80 Wide variety of industrial applications. T573 1.62 VH M (66) (218) (36) (12.5) 0.0022 4100 6000 80 Medium duty industrial and general traction T583 1.67 VH M (56) (289) (30) (12.5) motor application. Where threading is a concern in 0.0035 3600 7000 70 T606 1.73 VH M contaminated atmospheres and to minimize (76) (253) (36) (11) friction chatter. 0.0030 2700 8000 80 Where low humidity and selelctivity are T652 1.62 VH M (76) (190) (41) (12.5) concerns. 0.0030 4000 8000 80 Low friction and good commutation are T659 1.63 VH M (76) (282) (41) (12.5) primary concerns. 0.0027 4700 8000 80 High-speed transit car motors. T758 1.68 VH M (66) (331) (41) (12.5) 7 8

Electrographitic (continued)

Spec. Trans. Surface Normal Res. Strength Con- Speed Current Description and Application Brush Ω-in. Dens. lbf/in² tact Fric- ft/min Density Grade (µΩ-m) g/cm³ (kgf/cm²) Drop tion (m/sec) A/in² (A/cm²) Recommended for: Off highway vehicle traction motors under 0.0025 4200 10000 80 T825 1.69 VH L severe conditions of high temperature, low (58) (359) (51) (12.5) humidity, and heavy loads. 0.0013 4000 6000 70 Brass collector rings and medium-duty T869 1.71 VH M (36) (282) (30) (11) commutating service. Where excellent low humidity and high 0.0020 4500 8000 80 T900 1.68 VH M brush temperature are primary concerns. (51) (317) (41) (12.5) Used extensively in traction motor service. Traction motors which require superior 0.0024 4200 8000 80 commutation and low friction under T959 1.68 VH M (61) (296) (41) (12.5) various duty cycles and low humidity conditions.

Graphite

Spec. Trans. Surface Normal Res. Strength Con- Speed Current Abra Description and Application Brush Ω-in. Dens. lbf/in² tact Fric- ft/min Density sive Grade (µΩ-m) g/cm³ (kgf/cm² Drop tion (m/sec) A/in² ness (A/cm²) Recommended for: 0.0007 750 16000 65 High-speed slip rings on turbo 634 1.28 VH L M (18) (53) (81) (10) alternators around the world. 0.0010 1300 12000 55 High-speed service where scrubbing H 1.36 VH M M (28) (92) (61) (8.5) action required. 0.0025 3000 8000 65 Industrial application that require a high HRG 1.90 VH L H (64) (211) (41) (10) polishing action. 0.00036 2900 8000 65 Contaminated atmospheres for light K816 1.83 M M M (13) (204) (41) (10) loads and low-voltage machines. Where a very high contact drop is 0.0400 3300 6000 40 primary consideration. Recommended PH 1.61 VH L L (1016) (232) (30) (6.2) for FHP motors with difficult commutating characteristics. Where exceptional riding and commutating ability is required. 0.0022 3600 5000 45 R310 1.75 VH M L Successful on 3600 RPM turbo exciters (76) (253) (25) (7) up to 60 kw size, motors and generators in paper mill, steel mill service. 0.0020 2400 6000 55 Similar to R310 but with greater load R312 1.73 VH M L (51) (169) (30) (8.5) capacity. 0.0007 3200 10000 65 Steel slip rings of alternators and R318 1.75 H M M (25) (225) (51) (10) synchronous motors. Where selectivity is primary concern. 0.0013 1000 12000 65 R320 1.35 H M M This grade has a very low coefficient of (33) (70) (61) (10) friction for high-speed service. Small, difficult to commutate machines 0.0220 3000 6000 55 such as amplidynes and non- R884 1.62 VH M M (762) (211) (30) (8.5) commutating pole motors used with SCR packages. 0.0020 4500 6000 55 Contaminated environments to reduce T341 1.79 VH M L (51) (317) (30) (8.5) threading and improve brush life. 0.0025 3700 8000 80 Battery truck motors where superior T990 1.83 VH M M (64) (260) (41) (12.5) commutating ability is required. 8 9

Metal Graphite

Spec. Trans. Surface Normal Res. Strength Con- Speed Current Abra % Description and Application Brush Ω-in. Dens. lbf/in² tact Fric- ft/min Density siven Met Grade (µΩ-m) g/cm³ (kgf/cm² Drop tion (m/sec) A/in² ess al (A/cm²) Recommended for: 24 – 50 volt DC motors and AC 0.0003 3200 6000 100 537 2.77 VH M L 48 motor collector rings where low (8) (225) (30) (15.5) humidity protection is required. High current/low voltage 0.00016 4700 6000 100 40 AJT 3.00 L L L motors exposed to high (4) (331) (30) (15.5) altitudes. Where high copper content 0.000006 3500 6000 150 ANK 4.95 L L M 75 and low humidity protection is (0.2) (246) (30) (23.3) needed. 0.000044 5000 4000 100 Applications of wound rotor AYK 2.64 M M L 40 (1.1) (352) (20) (15.5) motor rings up to 100 APSI. Appliance motors and other 0.0450 2300 4000 40 F83 2.02 VH L L 25 FHP applications and suitable (1143) (162) (20) (6.2) for low current densities. Low-voltage motors, particularly switch and signal 0.000014 3100 5000 125 equipment. Also used on L4 4.57 L H M 75 (0.38) (218) (25) (19.4) plating generators up to 15 volt and on brass slip rings of induction motors. 0.000125 3500 7000 100 Slip rings and low voltage M2650 2.80 L L L 50 (2.79) (246) (36) (15.5) motors (24 – 72 volts). 0.000025 3800 6000 110 Slip rings and low voltage M2665 3.50 L VL L 65 (0.76) (268) (30) (17) motors (6 – 24 volts). Slip rings and low voltage motors (6 – 24 volts). Also can 0.000008 3200 6000 125 M2675 4.25 L L M 75 be used on slip ring (0.23) (225) (30) (19.4) applications when higher current density is needed. 0.000015 8000 6000 150 Plating generators up to 15 M2688 5.40 L L M 88 (0.38) (563) (30) (23.3) volts and conductor rolls. Where very low contact drop, 0.000008 2400 4500 150 and low friction are required. M407 5.10 L M L 75 (0.2) (169) (23) (23.3) Also used on controllers and control equipment. 0.000015 8300 5000 140 Low-voltage machines and M540 5.40 L H M 85 (0.38) (584) (25) (21.7) grounding brushes. Low voltage, high current 0.000012 6000 4000 150 applications where long brush M5N 5.91 L M M 96 (0.3) (422) (20) (23.3) life and minimum collector wear is desired. Low-voltage DC motors and 0.00027 3000 6000 100 generators in the 24 to 72 volt M785 3.20 L H L 50 (7) (211) (30) (15.5) range and on brass slip rings of induction motors.

Grade Properties Tabulation Disclaimer

The information contained in this tabulation of material properties is based on experimental and / or historical trends and indicates guidelines for typical lots of materials. Choosing the correct grade for a particular application should not be based solely on physical properties. No guarantee of these properties is given or implied.

Advanced Materials & Technology 9 www.morganamt.com 10 Brush Request Form Six Steps to Identify a Carbon Brush

251 Forrester Dr. Greenville, SC 29607

Identification and Nameplate Information Describe The Shunt 1 4 Motor Generator Slip Ring

Manufacturer ______

Model #______Serial # ______

Total # Brushes _____ HP/KW ______RPM ______Commutator Slip Ring Volts_____ Amps _____ Actual Running Amps ______Shunt Location(s) ______

Describe The Application Shunt Length (in) ______2 Commutator Diameter ______(inches)

Slip Ring Synchronous Steel Ring Wound Rotor Bronze Ring

Diameter ______(inches)

Application General Industrial Steel Mill Tamed Rivet Insulated Measuring Length Papermill Elevator Mining Power Gen Other ______5 Describe The Brush Top

Describe The Brush 3 Circle Any Special Features

Top Bevel ______

Bot Bevel ______Pad Clip Other (for example: no pad or clip, convex, channel, etc.)

______Describe

Use calipers to measure Describe The Terminal (T), (W), and (L). Notice 6 differences in SR and Comm style brushes

Thickness (T) ______

Commutator Slip Ring Width (W) ______Tube Crimped Flag Yoke Button Eared

Length (L) ______Circle Terminal and Measure I.D. of Hole or Fork (in) ______

Solid Plytek Triply Quick Disconnect EZ Terminal

Advanced Materials & Technology Fill out the form and fax to 205.252.3600. Then call a www.morganamt.com Customer Service Representative at 800.858.3366. 11 Electrographite Grades Graphite Grades Metal Graphite Grades D L4 AY 234 537 634 N19 N39 N44 N48 N66 DE8

Applications M5N Applications T341 T990 T508 T550 T563 T566 T573 T583 T606 T652 T758 T825 T869 T900 T959 L932 L944 L966 T300 T416 T500 R310 R312 R318 R320 N964 SA35 SA45 SA50 M407 DE25 N6000 M2650 M2665 M2675 M2688 SA4542 SA4548 DE7000 DE9000 light load light load moderate load moderate load Paper Mills Paper Mills heavy loads heavy loads contamination contamination auxilary motors auxilary motors collector rolls collector rolls dc cranes dc cranes generators generators Steel Mills Steel Mills looper motors looper motors low voltage generators low voltage generators rolling mill motors rolling mill motors contamination contamination excavator generators excavator generators Mining Mining excavator motors excavator motors generators generators Elevators Elevators hoist motors hoist motors exciter generators exciter generators Power hydroelectric hydroelectric Power Generation steam turbine slip rings steam turbine slip rings Generation wind generators wind generators light loads light loads moderate load moderate load Industrial Industrial heavy loads heavy loads contamination contamination alternator alternator grid blower motor grid blower motor Railroad Railroad light rail light rail traction motor traction motor alternators alternators Off Highway grid blowers grid blowers Off Highway wheelmotors wheelmotors annealers annealers container cranes container cranes electric vehicle pump electric vehicle pump electric vehicle traction electric vehicle traction grounding grounding plastics plastics Misc Misc rotary conversion rotary conversion shears (hi inrush) shears (hi inrush) ski lifts ski lifts slip rings - bronze slip rings - bronze slip rings - steel slip rings - steel wound rotor motors wound rotor motors

Application / Grade Matrix Disclaimer

The applications of brushes to all types of electrical machines is numerous and varied. This grade / application matrix is intended to give general recommendation guidelines for many of those applications. These recommendations are the product of intensive research, development, and experience of our Application Engineers in both the laboratory and in the field and cover a wide range of service conditions. This process is a continuous development program and we are always striving to recommend the best grade for each application. 12 Electrographite Grades Graphite Grades Metal Graphite Grades D L4 AY 234 537 634 N19 N39 N44 N48 N66 DE8

Applications M5N Applications T341 T990 T508 T550 T563 T566 T573 T583 T606 T652 T758 T825 T869 T900 T959 L932 L944 L966 T300 T416 T500 R310 R312 R318 R320 N964 SA35 SA45 SA50 M407 DE25 N6000 M2650 M2665 M2675 M2688 SA4542 SA4548 DE7000 DE9000 light load light load moderate load moderate load Paper Mills Paper Mills heavy loads heavy loads contamination contamination auxilary motors auxilary motors collector rolls collector rolls dc cranes dc cranes generators generators Steel Mills Steel Mills looper motors looper motors low voltage generators low voltage generators rolling mill motors rolling mill motors contamination contamination excavator generators excavator generators Mining Mining excavator motors excavator motors generators generators Elevators Elevators hoist motors hoist motors exciter generators exciter generators Power hydroelectric hydroelectric Power Generation steam turbine slip rings steam turbine slip rings Generation wind generators wind generators light loads light loads moderate load moderate load Industrial Industrial heavy loads heavy loads contamination contamination alternator alternator grid blower motor grid blower motor Railroad Railroad light rail light rail traction motor traction motor alternators alternators Off Highway grid blowers grid blowers Off Highway wheelmotors wheelmotors annealers annealers container cranes container cranes electric vehicle pump electric vehicle pump electric vehicle traction electric vehicle traction grounding grounding plastics plastics Misc Misc rotary conversion rotary conversion shears (hi inrush) shears (hi inrush) ski lifts ski lifts slip rings - bronze slip rings - bronze slip rings - steel slip rings - steel wound rotor motors wound rotor motors

Application / Grade Matrix Disclaimer

The applications of brushes to all types of electrical machines is numerous and varied. This grade There is a total cost consideration of commutators / slip rings and brushes when making decisions to / application matrix is intended to give general recommendation guidelines for many of those apply a brush material. A balance between good brush life versus commutator or slip ring wear that applications. These recommendations are the product of intensive research, development, and must be calculated and should be the final basis for grade selection. experience of our Application Engineers in both the laboratory and in the field and cover a wide range of service conditions. This process is a continuous development program and we are always striving to There is no guarantee given or implied in these recommendations. recommend the best grade for each application. 13 - repeating light and - repeating light and - occurs when high energy - occurs when high energy Slot Bar Filming Slotlming patterns related to the number Bar dark fi Filming lming patterns related to the number dark fi of armature coils per slot. of This armaturepattern dependentcoils is per slot.on This thepattern dependentmachineis usually not a function of the brush grade. on designthe and machineusually not a function of the brush grade. design and Copper Drag transfers copper in a molten state. These particles become coated by contaminants from the surrounding environment properly oxidize not do and or treatment brush the lm on surface. the to commutator form the fi the of edge the at accumulate particles These insulating the across shorting eventually bar, addressed be to needs condition This mica. immediately when discovered or seriousdamage may occur.commutator bar edges is necessary to stop Chamfering the progression of this condition. the Slot Bar Burning - results in commutator Slot Bar Burning - results in commutator erosion of every second, erosionthird, of bar or everydepending fourth on second, the third,winding designbar or ofdepending fourththe on armature.the winding design ofImproper the brusharmature.brush material,design Improperor electricalbrushbrush material,the designmachine can cause adjustmentthis condition. This or of electrical commutator the the machine can cause adjustmentthis condition. This damages severely condition of commutator the damages severely condition and reduces brush life. and reduces brush life. Copper Copper Drag transfers copper in a molten state. These particles become coated by contaminants from the surrounding environment properly oxidize not do and or treatment brush the lm on surface. the to commutator form the fi the of edge the at accumulate particles These insulating the across shorting eventually bar, addressed be to needs condition This mica. immediately when discovered or seriousdamage may occur.commutator bar edges is necessary to stop Chamfering the progression of this condition. the Unsatisfactory Conditions Unsatisfactory Conditions - this nonuniform filming- this nonuniform filming condition is the most common appearance. is condition the most appearance. common is condition the most appearance. common in The tolerances the accumulated machine contact brush roundness, in The tolerances the commutator accumulated machine as such contact brush roundness, commutator as such pressure, unequal of type this to pressure,contribute all magneticvapors chemical unequalfields of type this to contribute all magneticvapors development. lm andchemical fi fields development. lm and fi Blotchy Film Blotchy Film Grooving - is exhibited the is uniform that circumferential brush, the of width the wear, dust abrasive Excessive commutator. the on can brush abrasive an or atmosphere the in cause this condition. Extreme light spring this cause also can psi) 1.5 (below pressure can condition. motors ventilated Proper force brush on applications air and the ltering fi Some people reduce the commutator wear. call this “Ridging” because of the resulting ridges on each side of the groove. - is the erosion of the trailing the of erosion the is - Burning Bar machine Failed bar. trailing the of erosion the is - commutator Burning Bar the of machine edge Failed bar. symmetry commutator electrical the of edge maladjusted components, symmetry electrical brush maladjusted commutating poor a components, or machine the of brush commutating poor a or machine the of can result in bar burning. If not corrected, can result in bar commutator burning. severe cause If can not condition corrected, this commutator severe cause can condition ashover. this damage or a fl ashover. damage or a fl Grooving - is exhibited the is uniform that circumferential brush, the of width the wear, dust abrasive Excessive commutator. the on can brush abrasive an or atmosphere the in cause this condition. Extreme light spring this cause also can psi) 1.5 (below pressure can condition. motors ventilated Proper force brush on applications air and the ltering fi Some people reduce the commutator wear. call this “Ridging” because of the resulting ridges on each side of the groove. NAT SCP 4/08 INDEXX NAT SCP 4/08 INDEXX NAT Satisfactory Conditions Satisfactory Conditions Unsatisfactory Conditions Unsatisfactory Conditions - if uniform over- ifthe uniformentire over the entire Dark Film Dark commutator Film surface is commutatoracceptable. conditionsurface This is acceptable.can conditionbe filmingThis the canresult be brush filmingvapor ofchemical theof presence the or densities a result grade,high brush vapor ofchemical of presence the or densities a higher contamination. grade,high current highercontamination. current commutator in results - Burning Bar Pitch bars being eroded in a pattern related to progressing arms, brush of number the 1/2 into a pattern equal to the number of brush arms. This condition is caused by a cyclic as such disturbance electrical or mechanical shafts, misaligned armature, unbalanced an foundation, weak bearings, bad shaft, bent connection. riser poor a or equalizers failed a in result will condition this corrected not If ashover. fl Bright Spots - a freckled are appearance that of machines by caused usually lm Bright Spots - fi a the freckled are appearance that of machines by caused usually lm fi the the If cycles. overload frequent to subjected machine a lm, the If cycles. overload frequent to subjected fi the only disturb spots bright machine this a lm, with time of fi the periods only disturb long spots bright for operate can this with time of the periods begins, long for transfer operate metal can severe If condition. the begins, bar transfer metal dangerous to severe If progress condition. could spots bright bar dangerous to progress could spots lm stripping. bright burning or fi lm stripping. burning or fi - results in commutator in results - Burning Bar Pitch bars being eroded in a pattern related to progressing arms, brush of number the 1/2 into a pattern equal to the number of brush arms. This condition is caused by a cyclic as such disturbance electrical or mechanical shafts, misaligned armature, unbalanced an foundation, weak bearings, bad shaft, bent connection. riser poor a or equalizers failed a in result will condition this corrected not If ashover. fl Concerned Conditions Concerned Conditions COMMUTATOR SURFACE CONDITIONS SURFACE COMMUTATOR CONDITIONS SURFACE COMMUTATOR - over the entire commutator - over the entire commutator - is machining of the commutator commutator the of machining is - - is machining of the commutator commutator the of machining is - - of only the fi lm is not detrimental detrimental not is lm fi the detrimental only not of is - lm fi the only of - Call our Application Engineering Dept. your if you would like help improving Commutator Condition or Brush Performance. Light Film conditions normal many the of Light one is Film surface conditions normal many the of one is surface often seen on a well functioning machine. often seen on Film a tone is well dependent on functioning the brush machine. grade Film tone is dependent on the and current density. brush grade and current density. Threading by copper particles in the brush face. The excessive copper transferto low springoccurrs pressure, trapped are particles These due lightcontamination. loading or in the porous carbonharden, creating a tool brushthat machines machine The andor surface. commutator the gauls work can operate for long periods of time with and commutator reduced but condition, this brush life will be experienced. 864-458-7777 or 1-800-543-6322 864-458-7777 or 1-800-543-6322 Call our Application Engineering Dept. your if you would like help improving Commutator Condition or Brush Performance. Streaking Streaking to the commutator. Brush and commutator to the commutator. metal If Brush condition. this in risk and at not are life commutator progress will condition metal If condition. this in this risk at not are life develops, transfer progress will condition this develops, transfer into threading. This into type lming threading. ofbe can dependent fi on current This density type or lming brush ofbe can dependent fi on grade. current density or brush grade. by copper particles in the brush face. The excessive copper transferto low springoccurrs pressure, trapped are particles These due lightcontamination. loading or in the porous carbonharden, creating a tool brushthat machines machine The andor surface. commutator the gauls work can operate for long periods of time with and commutator reduced but condition, this brush life will be experienced. 14 Threading COMMUTATOR SURFACE CONDITIONS

Satisfactory Conditions

Light Film - over the entire commutator Dark Film - if uniform over the entire Blotchy Film - this nonuniform filming Slot Bar Filming - repeating light and surface is one of the many normal conditions commutator surface is acceptable. This condition is the most common appearance. dark fi lming patterns related to the number often seen on a well functioning machine. condition can be the result of a high The accumulated tolerances in the machine of armature coils per slot. This pattern is Film tone is dependent on the brush grade filming brush grade, higher current such as commutator roundness, brush contact dependent on the machine design and and current density. densities or the presence of chemical vapor pressure, unequal magnetic fields and usually not a function of the brush grade. contamination. chemical vapors all contribute to this type of fi lm development. Concerned Conditions Unsatisfactory Conditions

Streaking - of only the fi lm is not detrimental Bright Spots - a freckled appearance of Bar Burning - is the erosion of the trailing Slot Bar Burning - results in commutator to the commutator. Brush and commutator the fi lm usually caused by machines that are edge of the commutator bar. Failed machine erosion of every second, third, or fourth life are not at risk in this condition. If metal subjected to frequent overload cycles. If the components, maladjusted electrical symmetry bar depending on the winding design of transfer develops, this condition will progress bright spots disturb only the fi lm, a machine of the machine or a poor commutating brush the armature. Improper brush material, into threading. This type of fi lming can can operate for long periods of time with this can result in bar burning. If not corrected, brush design or electrical adjustment of be dependent on current density or brush condition. If severe metal transfer begins, the this condition can cause severe commutator the machine can cause this condition. This grade. bright spots could progress to dangerous bar damage or a fl ashover. condition severely damages the commutator burning or fi lm stripping. and reduces brush life. Unsatisfactory Conditions

Threading - is machining of the commutator Pitch Bar Burning - results in commutator Grooving - is the uniform circumferential Copper Drag - occurs when high energy by copper particles in the brush face. The bars being eroded in a pattern related to wear, the width of the brush, that is exhibited transfers copper in a molten state. These excessive copper transfer occurrs due 1/2 the number of brush arms, progressing on the commutator. Excessive abrasive dust particles become coated by contaminants to low spring pressure, light loading or into a pattern equal to the number of brush in the atmosphere or an abrasive brush can from the surrounding environment or the contamination. These particles are trapped arms. This condition is caused by a cyclic cause this condition. Extreme light spring brush treatment and do not oxidize properly in the porous carbon brush and work mechanical or electrical disturbance such as pressure (below 1.5 psi) can also cause this to form the fi lm on the commutator surface. harden, creating a tool that machines or an unbalanced armature, misaligned shafts, condition. Proper brush applications and These particles accumulate at the edge of the gauls the commutator surface. The machine bent shaft, bad bearings, weak foundation, fi ltering the air on force ventilated motors can bar, eventually shorting across the insulating can operate for long periods of time with failed equalizers or a poor riser connection. reduce the commutator wear. Some people mica. This condition needs to be addressed this condition, but reduced commutator and If not corrected this condition will result in a call this “Ridging” because of the resulting immediately when discovered or serious brush life will be experienced. fl ashover. ridges on each side of the groove. damage may occur. Chamfering the commutator bar edges is necessary to stop Call our Application Engineering Dept. the progression of this condition. if you would like help improving your Commutator Condition or Brush Performance.

864-458-7777 or 1-800-543-6322 NAT SCP 4/08 INDEXX 251 Forrester Drive Greenville, SC 29607-5328 USA 1.800.543.6322 1.864.458.7777 ® www.morganamt.com 64011023 CPO1 9/09 500 NAT