碳刷技术资料

Profile r MAS - Commuta tor - Ra dia l Plot
2.0 1 200 0.0 20 -2.0 Brush Path 2
180
40
Radial Scale ( +/- 2.0 Mils)
160
Brushes
60
Commutator
140
-2.0
80
0.0
120 100
-2.0
0.0
2.0
These brushes have an impossible task of trying to contact each commutator segment with 3.94 mils TIR & 2.32 MBTB
Profile r MAS - Commuta tor - Ra dia l Plot
Do not mix brush grades or brush springs
Constant Force Springs
Are not constant force
Must first be uncoiled approx. 1/2 dia. of coil
Cannot handle excessive oscillation
A reasonably round commutator is needed
Cannot carry current because current causes the spring to fatigue (lose force) Have a + / - 10% tolerance Are not adjustable
Mechanical Wear
Friction
Spring Force
Brush Wear - Electrical
( Sparking )
Rough Commutator or SR Extended periods of HIGH loads Weak or sluggish Springs High mica Improper Interpole Field strength Wrong Interpole bolts Wrong brush construction Improper neutral setting
Commutator Condition Indicators
Situation Runout ( TIR ) Bar to Bar Variance
( MBTB )
Undercut Depth
NEW
Less than Less than .0015 .0002
.050 or more
Less than Less than IN .003 .0003 SERVICE
-2.0
R eco rd ing start 18 Jun 2003 ( 7:47:42 am ) (Actu al) Size (213) 213 Bars TIR 3.94 m il : 55-3 Max B TB 2.32 : 55-56 Mean B TB Std d ev 0.194 0.259 Su sp ect H i Mica R emark 0 0
Calculating Brush Pressure
BRUSH PRESSURE
Lbs per Sq. Inch
Measured Spring Force * Brush Thickness
( inches )
( PSI )
x
Brush Width
( inches )
* Average of IN & OUT movement
-2.0
Mean B TB Std dev 0.086 0.082 Su spect H i Mica R emark 0 0
0.0
2.0
These brushes will have a harder job trying to contact each Commutator segment with 3.39 mils TIR & .44 Max. BTB
Recommended Brush PSI Range 3.5 to 6 3 to 8 5 to 10 3 to 4 2 to 2.75 3 to 5
Application
General Industrial Motors Fractional HP Motors Traction Motors Slip Rings – Low Speed, Graphite Grade Slip Rings – High Speed, Graphite Grade Metal Graphite Grades
Constant Force Spring Characteristic
Brush Wear Rate
Spring Force
New Brush Wear Length
Used up
New
Bead Blasted
Current Damaged
A reasonably round commutator surface is needed to expect good brush performance, brush life, commutator, brush holder and spring life.
( PSI )
Wear Rate
10
11
Brush Pressure
Total Brush Wear
4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 0 1 2 3
Optimum Range
Wear Rate
4
5
6
7
8
9
( PSI )
10
11
Brush Pressure
How Much Brush Pressure ?
-2.0
0.0
2.0
These brushes have an easy job of conducting current to each Commutator segment with 1.18 mils TIR.
Profile r MAS - Commuta tor - Ra dia l Plot
2.0 1 200 0.0 20 -2.0 Track 2
180
40
Radial Scale ( +/- 2.0 Mils)
160
60
140
-2.0
80
0.0 120 100 2.0
R eco rd ing Plo t Track 2 R ec# 2
2.0 0.0 -2.0
(Actu al) Size (211) 211 Bars TIR 3.39 mil : 1-86 Max B TB 0.44 : 8Baidu Nhomakorabea-87 R eco rd in g start 19 Mar 2002 ( 4:06:18 pm )
.020 or more
NEEDS More than More than .003 .0003 REPAIR
.010 or less
Main Purpose of a Brush
To conduct electrical current from it, to a rotating Commutator or Slip Ring
Brush Pressure Spring Force Mechanical Brush Wear Electrical Brush Wear
Brush Wear - Mechanical
Rough Commutator or Slip Ring High Brush Pressure High Surface Speeds High Mica Abrasive Atmosphere High Vibration or Shock loads Improper brush arm spacing
0.0
R ec# 4
-2.0
R eco rd ing start 18 Jun 2003 ( 7:47:42 am ) (Actu al) Size (213) 213 Bars TIR 3.94 m il : 55-3 Max B TB 2.32 : 55-56 Mean B TB Std d ev 0.194 0.259 Su sp ect H i Mica R emark 0 0
Profile r MAS - Commuta tor - Ra dia l Plot
2.0 1 Brush Path 2 200 0.0 20
-2.0
180
40
Radial Scale ( +/- 2.0 Mils)
160
60
140
80 -2.0
0.0 120 100 2.0 2.0
R eco rd ing Brush Path 2 Plot
The proper amount of brush pressure against the commutator or slip ring depends on the application and/or the brush grade. To calculate the brush pressure; you need to know or measure the spring force and the brush thickness and width. Brush T x W = the cross sectional area. Brushes that contact the commutator at an angle do have more contact area than the product of their T x W, but it is usually not a significant difference, so only the cross sectional area is used.
In the case of a DC Motor with a Commutator, it needs to conduct current to each and every commutator segment Intimate contact with each commutator segment is required to conduct current without arcing ( Arcing or sparking is current going through air )
-2.0
0.0
2.0
You can hear brush clatter and see sparking when comm. TIR is excessive. Poor brush life is also realized.
These brushes are from a motor with a very rough comm. Brush wear is different since TIR of each brush path is different.
2.0 1 Brush Path 2 0.0
-2.0
** *
180
200 20
*
*
40
Radial Scale ( +/- 2.0 Mils)
160
60
** * *
-2.0 0.0 2.0 2.0
R eco rd ing Brush Path 2 Plot
140
80
***
120 100 0.0
R ec# 4
2.0 2.0
R eco rd ing Brush Path 2 Plot
0.0
R ec# 2
-2.0
R eco rd ing start 12 Mar 2003 ( 8:48:43 am ) (Actu al) Size (209) 209 Bars TIR 1.18 m il : 45-10 Max B TB 0.47 : 10-11 Mean B TB Std d ev 0.078 0.075 Su sp ect H i Mica R emark 0 0
Electrical Wear
Sparking
Brush Pressure
BRUSH PRESSURE and How it Relates to BRUSH WEAR
Total Brush Wear
4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 0 1 2 3 4 5 6 7 8 9