Upload
dangtu
View
226
Download
5
Embed Size (px)
Citation preview
The Effect of DC Machine The Effect of DC Machine Adjustment onAdjustment on Loop UnbalanceLoop Unbalance
WMEA, Edmonton, Alberta, CanadaWMEA, Edmonton, Alberta, CanadaJune 11June 11--13, 200813, 2008
Rich Hall Rich Hall –– Morgan AM&TMorgan AM&T
Jim Shackelford Jim Shackelford –– Peabody EnergyPeabody Energy
Technical ContributorTechnical Contributor
Jason Conrad Jason Conrad –– GE Canada GE Canada
Peterborough, Ontario, CanadaPeterborough, Ontario, Canada
Dragline Generator LoopsDragline Generator Loops
Loop 1Loop 1 Loop 2Loop 2
HG1HG1
HM1HM1
HG3HG3
HM3HM3
HG2HG2
HM2HM2
HG4HG4
HM4HM4
Dragline Loops ContainDragline Loops Contain
•• Direct Current GeneratorsDirect Current Generators•• Direct Current MotorsDirect Current Motors•• Ammeter ShuntsAmmeter Shunts•• CablesCables•• ConnectionsConnections
Dragline Generator LoopsDragline Generator Loops Design BenefitsDesign Benefits
• Multiple units in each loop “average out” some of the variation in individual generators and motors, cabling, etc.
• Multiple motors and generators “average out” the effect of temperature variations around the house
• Multiple loops give some degree of control of the machine if one loop is lost
Loop BalanceLoop Balance
Ideally, the loops behave exactly the Ideally, the loops behave exactly the same as each other under all conditionssame as each other under all conditions
Visually, they would look like a Visually, they would look like a wellwell--choreographed synchronized choreographed synchronized
swim teamswim team
Loop BalanceLoop Balance cont.cont.
•• This means each generator behaves This means each generator behaves like every other generatorlike every other generator
•• Each motor behaves like every other Each motor behaves like every other motormotor
•• Each loopEach loop’’s cables and connections s cables and connections have the same resistance as each other have the same resistance as each other looploop
These loops act electrically in These loops act electrically in parallelparallel
•• If the generators in one loop produce If the generators in one loop produce more Voltage than the generators in other more Voltage than the generators in other loops, that loop will draw more currentloops, that loop will draw more current
•• If the motors in one loop If the motors in one loop ““trytry”” to run to run faster than the motors in other loops, they faster than the motors in other loops, they cannot because they are geared together, cannot because they are geared together, but that loop will draw more currentbut that loop will draw more current
These loops act electrically in These loops act electrically in parallelparallel
•• If the resistances of the cables and If the resistances of the cables and connections are lower in one loop than connections are lower in one loop than the other loops, that loop will draw the other loops, that loop will draw more currentmore current
So what??So what??•• Unbalanced loop currents may cause Unbalanced loop currents may cause
excessive torque in some loops, cause excessive torque in some loops, cause increased mechanical wear and take increased mechanical wear and take life out of couplings, gears, and life out of couplings, gears, and structural parts of the machinestructural parts of the machine
•• Unbalanced loop currents may result in Unbalanced loop currents may result in too little torque in some loops and too little torque in some loops and reduce the productivity of the draglinereduce the productivity of the dragline
Other ProblemsOther Problems
•• Unbalanced loop currents may result in Unbalanced loop currents may result in increased brush and commutator wearincreased brush and commutator wear
•• Unbalanced loop currents may result in Unbalanced loop currents may result in flashoversflashovers
•• Unbalanced loop currents may trip the Unbalanced loop currents may trip the loop overcurrentloop overcurrent
•• Unbalanced loop currents may cause Unbalanced loop currents may cause the generator field overcurrent to tripthe generator field overcurrent to trip
Bigger Problems!!!Bigger Problems!!!
•• Unbalanced loop currents may result in Unbalanced loop currents may result in overheating some generators or motorsoverheating some generators or motors
•• Badly unbalanced loop currents may Badly unbalanced loop currents may cause the sync motors to pull out of cause the sync motors to pull out of synchronization, especially on weak synchronization, especially on weak power systemspower systems
ResultsResults
•• This may cause damage to equipment, This may cause damage to equipment, loss of productivity, increased loss of productivity, increased downtime and increased repair costsdowntime and increased repair costs
•• Rule of thumb in the business loss Rule of thumb in the business loss insurance industry: the cost of the insurance industry: the cost of the repair is 10% of the business lossrepair is 10% of the business loss
How much voltage does it take to How much voltage does it take to drive rated current?drive rated current?
•• The rating of a GE 1045 KW generator The rating of a GE 1045 KW generator is 475 Volts and 2200 Amperes.is 475 Volts and 2200 Amperes.
•• It does not take 475 Volts to drive rated It does not take 475 Volts to drive rated current in the loop, however.current in the loop, however.
How much voltage does it take to How much voltage does it take to drive rated current?drive rated current?
•• The answer The answer –– about 20 Volts per about 20 Volts per generator!!!generator!!!
How much voltage does it take to How much voltage does it take to drive rated current?drive rated current?
•• When the machines are in a When the machines are in a ““motoringmotoring”” quadrant, the generators are generating quadrant, the generators are generating an electro motive force (EMF), but the an electro motive force (EMF), but the motors are motors are also generating an generating an electromotive force that opposes the electromotive force that opposes the generator EMF and it is called a counter generator EMF and it is called a counter EMF (CEMF).EMF (CEMF).
How much voltage does it take to How much voltage does it take to drive rated current?drive rated current?
•• It is the sum of the generator Voltages It is the sum of the generator Voltages minus the sum of the motor Voltages in minus the sum of the motor Voltages in the loop that drives loop current.the loop that drives loop current.
•• This Voltage divided by the loop This Voltage divided by the loop resistance gives the loop current.resistance gives the loop current.
Dragline Generator LoopDragline Generator Loop
Loop 1Loop 1
HG1HG1
HM1HM1
HG3HG3
HM3HM3
++
++
++
++__
__
__
__Loop Loop CurrentCurrent
How much voltage does it take to How much voltage does it take to drive rated current?drive rated current?
•• The loop resistance is most easily The loop resistance is most easily determined at stall when the motors are determined at stall when the motors are not rotating or generating any CEMF.not rotating or generating any CEMF.
•• For a 1045 KW generator, about 40 Volts For a 1045 KW generator, about 40 Volts per generator drives stall current (2X rated per generator drives stall current (2X rated current or 4400 Amperes).current or 4400 Amperes).
•• Loop Resistance = Loop Resistance = (40V + 40V (40V + 40V –– 0V 0V -- 0V) 0V) = = 0.0181 Ohm0.0181 Ohm 4400 Amperes4400 Amperes
How much voltage does it take to How much voltage does it take to drive rated current?drive rated current?
•• It does not take a large Voltage It does not take a large Voltage imbalance to drive a lot of current when imbalance to drive a lot of current when you divide it by 0.0181!!!you divide it by 0.0181!!!
Standards for Loop Balance
•• 5% of stall current at stall conditions5% of stall current at stall conditions
•• 5% of stall current while running steady 5% of stall current while running steady (even at peak power)(even at peak power)
•• 10% of stall current during transient 10% of stall current during transient load changesload changes
How much voltage difference How much voltage difference does it take to be at the does it take to be at the recommended limits?recommended limits?
•• 5% of 4400 Amperes = 220 Amperes5% of 4400 Amperes = 220 Amperes
•• V = IR = 220 Amperes x 0.0181 Ohms V = IR = 220 Amperes x 0.0181 Ohms
V = 3.9 VoltsV = 3.9 Volts
•• So a 4 Volt difference between loops is So a 4 Volt difference between loops is all it takes to be at 5% of stall current! all it takes to be at 5% of stall current!
Four Quadrant OperationFour Quadrant Operation
1122
33 44
+ Vo
lts+
Volts
-- Vol
tsVo
lts
+ Amps+ Amps-- AmpsAmps
First QuadrantFirst QuadrantA
rmat
ure
Volts
Arm
atur
e Vo
lts
Armature AmpsArmature Amps
Commutation LimitsCommutation Limits
Loop 1Loop 1
Loop 2Loop 2
Unbalanced Loop Unbalanced Loop CurrentCurrent
Loop BalanceLoop Balance
•• Loop 1 is the control loop and is inside Loop 1 is the control loop and is inside the commutation limits, so it is OK.the commutation limits, so it is OK.
•• Loop 2 is the slave loop and is inside Loop 2 is the slave loop and is inside the commutation limits, so the the commutation limits, so the equipment is OK. It is equipment is OK. It is ““loafingloafing””, , however, so the dragline is working at however, so the dragline is working at less than capacity.less than capacity.
First QuadrantFirst QuadrantA
rmat
ure
Volts
Arm
atur
e Vo
lts
Armature AmpsArmature Amps
Commutation LimitsCommutation Limits
Loop 1Loop 1
Loop 2Loop 2
Unbalanced Loop Unbalanced Loop Current Current
Loop BalanceLoop Balance
•• Loop 1 is the control loop and is inside Loop 1 is the control loop and is inside the commutation limits, so it is OK.the commutation limits, so it is OK.
•• Loop 2 is the slave loop and is outside Loop 2 is the slave loop and is outside the commutation limits. This may lead the commutation limits. This may lead to commutation distress, flashovers, to commutation distress, flashovers, excessive wear of couplings and gears, excessive wear of couplings and gears, tripping of the machine, etc. tripping of the machine, etc.
Assembling DC MachinesAssembling DC Machines
•• To work properly together and to To work properly together and to commutate well, machines must be commutate well, machines must be built or rebuilt properly.built or rebuilt properly.
•• Following are GE factory tolerances Following are GE factory tolerances provided by GE Canada, Peterborough, provided by GE Canada, Peterborough, Ontario.Ontario.
GeneratorsGenerators
•• Pole centerline to pole centerline chord Pole centerline to pole centerline chord –– measured at both ends of machinemeasured at both ends of machine–– minimum to maximum values must not minimum to maximum values must not
differ by more than 0.125differ by more than 0.125”” (3.2 mm)(3.2 mm)
Pole Tip SpacingPole Tip Spacing
Difference Between A and B is Difference Between A and B is 1/81/8”” (3.2 mm) Maximum(3.2 mm) Maximum
AA BB
FrameFrame
GeneratorsGenerators
•• Brush Holder AssemblyBrush Holder Assembly–– holders to be set 0.070holders to be set 0.070”” to 0.080to 0.080”” from from
commutator surface (1.8 to 2.0 mm)commutator surface (1.8 to 2.0 mm)–– axial skew must not exceed one mica axial skew must not exceed one mica
thickness over the length of the thickness over the length of the commutatorcommutator
0.070 – 0.080” (1.8 – 2.0 mm)
Brush Box HeightBrush Box Height
GeneratorsGenerators
•• Circumferential brush spacing (paper Circumferential brush spacing (paper tape on commutator)tape on commutator)–– arcs measured from one brush toe to the arcs measured from one brush toe to the
next must be within 3/64next must be within 3/64”” (0.047(0.047”” or or 1.2 mm) 1.2 mm) (MAXIMUM)(MAXIMUM)
Commutator
Commutator
A
F
E
D
C
B
A = ______B = ______C = ______D = ______E = ______F = ______
Max. SpacingDiff. = ______
Target is .030”
On WestinghouseEquipment
Brush Spacing
Max. Spacing diff = .050” on GE equip.
GeneratorsGenerators
•• Air GapsAir Gaps–– all air gaps to be within +/all air gaps to be within +/--0.0070.007”” (0.18 mm)(0.18 mm)–– commutating pole air gaps may be commutating pole air gaps may be
different than main pole air gapsdifferent than main pole air gaps
Uneven And Tapered Air GapsUneven And Tapered Air Gaps
FrameFrame
PolePole
PolePole
FrameFrame
ArmatureArmature
Air Gap Taper GaugeAir Gap Taper Gauge
Air Gap MeasurementAir Gap Measurement
MotorsMotors
•• Pole centerline to pole centerline chord Pole centerline to pole centerline chord –– measured at both ends of machinemeasured at both ends of machine–– minimum to maximum values must not minimum to maximum values must not
differ by more than 0.125differ by more than 0.125”” (3.2 mm)(3.2 mm)
MotorsMotors
•• Brush Holder AssemblyBrush Holder Assembly–– holders to be set 0.070holders to be set 0.070”” to 0.080to 0.080”” from from
commutator surface (1.8 to 2.0 mm)commutator surface (1.8 to 2.0 mm)–– axial skew must not exceed one mica axial skew must not exceed one mica
thickness over the length of the thickness over the length of the commutatorcommutator
MotorsMotors
•• Circumferential brush spacing (paper Circumferential brush spacing (paper tape on commutator)tape on commutator)–– arcs measured from one brush toe to the arcs measured from one brush toe to the
next must be within 3/64next must be within 3/64”” (0.047(0.047”” or or 1.2 mm)1.2 mm)
MotorsMotors
•• Air GapsAir Gaps–– all air gaps to be within +/all air gaps to be within +/--0.0070.007”” (0.18 mm)(0.18 mm)–– commutating pole air gaps may be commutating pole air gaps may be
different than main pole air gapsdifferent than main pole air gaps
N = Number of TurnsN = Number of Turnsg = Air Gapg = Air Gap
NN
gg
φφ αα
N x N x ii
NN
eeii
φφ FluxFlux
SATURATION CURVESATURATION CURVE
FluxFluxin in
Air GapAir Gap
N x N x IIFF (Ampere Turns)(Ampere Turns)
Iron Saturation RegionIron Saturation Region
Air Gap Region
Air Gap Region
φφ
NN
ee
0 24
24
++--
Generated VoltsGenerated Volts
LLVV
Volts = E. M. F. = B x L Volts = E. M. F. = B x L xxVVwherewhere
B = Flux Density ( B = Flux Density ( φφ / area) / area) L= Length of the conductorL= Length of the conductorVV = Velocity of the conductor= Velocity of the conductor
IIFF
GeneratorGenerator
V V αα
B x L x B x L x VV
V (EMF) V (EMF) αα
B B αα
IIFieldField
MotorMotorV V ==
B x L x B x L x VV
V V αα
B x RPMB x RPM
RPM RPM αα VoltsVolts α α VoltsVoltsBB IIFieldField
SpeedSpeed
TorqueTorqueF F α α B x IB x IAA x x LLTorque = Force x RadiusTorque = Force x RadiusTorque Torque αα
B x IB x IAA
BB
LL
rr( Flux Density )( Flux Density )
MotorMotor
V V αα
B x L x B x L x VV
V V α α B x L x RPM B x L x RPM
V (CEMF) V (CEMF) αα
B x RPM B x RPM
αα
IIFieldField x RPMx RPM
Generator Generator Data SheetData Sheet
00
Arm
atur
e Vo
ltsA
rmat
ure
Volts
100100
200200
300300
400400
500500
600600
Field AmpsField Amps22 44 66 88 1010 1212 1414 1616 1818 2020
..
..
No Load Saturation No Load Saturation CurveCurve
MCF866B, 836 KW, 475 Volt, MCF866B, 836 KW, 475 Volt, 1760 Ampere, 1200 RPM1760 Ampere, 1200 RPM
Load Curve Load Curve –– 836 KW Gen.836 KW Gen.Armature VoltsArmature Volts Arm. AmpsArm. Amps Field AmpsField Amps
600600 00 18.918.9575575 11201120 18.618.6550550 22302230 18.618.6450450 25002500 13.513.5350350 27702770 11.211.2250250 30303030 9.49.44040 36003600 6.26.2
Adjusting DC Machines Adjusting DC Machines -- FactoryFactory
•• Black Band MethodBlack Band Method
•• See the paper See the paper ““NECP NECP –– Tuning DC Tuning DC Motors and Generators Motors and Generators –– Jun 07Jun 07”” on on the WMEA web site the WMEA web site wmea.netwmea.net for other for other methods of tuning DC machinesmethods of tuning DC machines
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
XX No Load Band No Load Band Center on Buck Center on Buck Side (Strong)Side (Strong) Corrective action Corrective action –– shift shift
brush rigging with rotation brush rigging with rotation (motor) or against rotation (motor) or against rotation (generator)(generator)
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
XXNo Load Band No Load Band Center on Boost Center on Boost Side (Weak)Side (Weak)
Corrective action Corrective action –– shift shift brush rigging against brush rigging against rotation (motor) or with rotation (motor) or with rotation (generator)rotation (generator)
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
xx
xx
xx
xx
xx
xx
Band CenterBand Center
Band Center on Boost Side Band Center on Boost Side (Weak)(Weak)
Corrective Action Corrective Action –– Remove Remove nonmagnetic shims, add magnetic nonmagnetic shims, add magnetic shimsshims
No sparking in black area, sparking outside black area
Buck Boost CurveBuck Boost Curve
xxLoad Amps (%)Load Amps (%)
Corrective Action Corrective Action –– Remove Remove magnetic shims, add non magnetic magnetic shims, add non magnetic shimsshims
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
XX
XX
5050 100100 150150
xx
xx
xx
xx
xx
Band CenterBand Center
Band Center on Band Center on Buck Side Buck Side (Strong)(Strong)
Sparking with no buck or boostSparking with no buck or boost
Voltage or RPM Regulation DefinedVoltage or RPM Regulation Defined
Armature AmpsArmature Amps
Volts
or R
PMVo
lts o
r RPM
Increased Voltage or RPM RegulationIncreased Voltage or RPM Regulation
Decreased Voltage or RPM RegulationDecreased Voltage or RPM Regulation
Generator Generator –– increased main pole air gapincreased main pole air gap
Saturation CurveSaturation Curve
Volts
Volts
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
Volts
Volts
BeforeBefore
AfterAfter
Regulation decreasesRegulation decreases
Generator Generator –– decreased main pole air gapdecreased main pole air gap
Saturation CurveSaturation Curve
Volts
Volts
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
Volts
Volts
BeforeBefore
AfterAfter
Regulation increasesRegulation increases
Generator Generator –– increased comm pole air gap increased comm pole air gap or add nonmagnetic shimsor add nonmagnetic shims
Saturation CurveSaturation Curve
Volts
Volts
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
Volts
Volts
BeforeBefore
AfterAfter
No EffectNo EffectRegulation increasesRegulation increases
Generator Generator –– decreased comm pole air gap decreased comm pole air gap or remove nonmagnetic shimsor remove nonmagnetic shims
Saturation CurveSaturation Curve
Volts
Volts
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
Volts
Volts
BeforeBefore
AfterAfter
No EffectNo Effect
Regulation deceasesRegulation deceases
Generator Generator –– brush shift with rotationbrush shift with rotation
Saturation CurveSaturation Curve
Volts
Volts
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
Volts
Volts
BeforeBefore
AfterAfter
No EffectNo EffectRegulation increasesRegulation increases
Generator Generator –– brush shift against rotationbrush shift against rotation
Saturation CurveSaturation Curve
Volts
Volts
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
Volts
Volts
BeforeBefore
AfterAfter
No EffectNo EffectRegulation decreases Regulation decreases
Motor Motor –– increased main pole air gapincreased main pole air gap
Saturation CurveSaturation Curve
Volts
/ R
PMVo
lts /
RPM
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
RPMRPM
BeforeBefore
AfterAfter
Regulation increasesRegulation increases
Motor Motor –– decreased main pole air gapdecreased main pole air gap
Saturation CurveSaturation Curve
Volts
/ R
PMVo
lts /
RPM
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
RPMRPM
BeforeBefore
AfterAfter
Regulation decreasesRegulation decreases
Motor Motor –– increased comm pole air gap or increased comm pole air gap or add nonmagnetic shimsadd nonmagnetic shims
Saturation CurveSaturation Curve
Volts
/ R
PMVo
lts /
RPM
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
RPMRPM
BeforeBefore
AfterAfter
Regulation increasesRegulation increasesNo EffectNo Effect
Motor Motor –– decreased comm pole air gap or decreased comm pole air gap or remove nonmagnetic shimsremove nonmagnetic shims
Saturation CurveSaturation Curve
Volts
/ R
PMVo
lts /
RPM
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
RPMRPM
BeforeBefore
AfterAfter
Regulation decreasesRegulation decreasesNo EffectNo Effect
Motor Motor –– Brush shift with rotationBrush shift with rotation
Saturation CurveSaturation Curve
Volts
/ R
PMVo
lts /
RPM
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
RPMRPM
BeforeBefore
AfterAfter
Regulation increasesRegulation increasesNo EffectNo Effect
Motor Motor –– Brush shift against rotationBrush shift against rotation
Saturation CurveSaturation Curve
Volts
/ R
PMVo
lts /
RPM
Field AmpsField Amps Armature AmpsArmature Amps
RegulationRegulation
RPMRPM
BeforeBefore
AfterAfter
Regulation decreasesRegulation decreasesNo EffectNo Effect
Voltage Regulation Voltage Regulation –– Shunt GeneratorShunt Generator
Armature AmpsArmature Amps
Volts
Volts
Low Voltage RegulationLow Voltage Regulation
Voltage Regulation Voltage Regulation –– Shunt GeneratorShunt Generator
Armature AmpsArmature Amps
Volts
Volts
Low Voltage RegulationLow Voltage Regulation
Delta AmpsDelta Amps
Delta Delta VoltsVolts
Voltage Regulation Voltage Regulation –– Differential Differential Compound GeneratorCompound Generator
Armature AmpsArmature Amps
Volts
Volts
Higher Voltage RegulationHigher Voltage Regulation
Delta AmpsDelta Amps
Delta Delta VoltsVolts
Differentially Compound Differentially Compound GeneratorsGenerators
•• Differentially compound generators Differentially compound generators limit loop current unbalances, as limit loop current unbalances, as generators that are more heavily loaded generators that are more heavily loaded (loop unbalance) will drop in voltage (loop unbalance) will drop in voltage and shed some load.and shed some load.
•• This helps, of course, but does not This helps, of course, but does not ““curecure”” loop unbalance.loop unbalance.
Machine Adjustments and Loop Machine Adjustments and Loop Balance SummaryBalance Summary
•• DC machines must be built to accepted DC machines must be built to accepted tolerances of air gaps, brush spacing, brush tolerances of air gaps, brush spacing, brush box heights, pole spacing, box heights, pole spacing, commcomm pole bolt pole bolt material, etc. to be as much alike as possible material, etc. to be as much alike as possible for the machines to commutate well and for the machines to commutate well and share load.share load.
•• Connections within the machines must be Connections within the machines must be tight to minimize variation in excitation tight to minimize variation in excitation currents and loop resistance.currents and loop resistance.
Machine Adjustments and Loop Machine Adjustments and Loop Balance Summary cont.Balance Summary cont.
•• When machines are disassembled and When machines are disassembled and reassembled, it is important to keep reassembled, it is important to keep track of shims, especially commutating track of shims, especially commutating pole shims. Both the thickness and pole shims. Both the thickness and order of shims are important! There is order of shims are important! There is not an easy way to correct interpole not an easy way to correct interpole shimming in the field, so care with the shimming in the field, so care with the machines when working on them in machines when working on them in shops is critical.shops is critical.
Machine Adjustments and Loop Machine Adjustments and Loop Balance Summary cont.Balance Summary cont.
•• There are many things that can contribute to There are many things that can contribute to commutation issues: rough commutators, commutation issues: rough commutators, symmetry of assembly, brush grades and symmetry of assembly, brush grades and construction, faulty machine components construction, faulty machine components and electrical connections. Sometimes and electrical connections. Sometimes people try to people try to ““fixfix”” machines by tuning them machines by tuning them up with neutral adjustments. Remember up with neutral adjustments. Remember –– this affects machine output and loop this affects machine output and loop balance, and you cannot balance, and you cannot ““adjust outadjust out”” these these underlying causes of commutation distress.underlying causes of commutation distress.
Field Process to Address Field Process to Address Loop UnbalancesLoop Unbalances
• Take Time versus: Drive Reference, Armature Volts and Amps, and Motor Field Current
• Make Stud to Stud Spacing Correct• Set Neutral (on GE Generator 1/8” with Rotation)• Adjust Generator Air Gaps to Ensure that the Sum of
the Volts in Each Loop are Equal within 2.5 Volts per Generator in the Loop ( 4 Generators in the Loop – 10 Volts)
• Trim Motor Fields “As Necessary”• Adjust Motor Neutral As “Last Resort” (Should be at
Neutral – Not with or Against Rotation)• If Possible Re-wire the Motion to Two Loops
Oversize HoleOversize HoleUse Use ½”½” Thin WallThin WallConduit to CenterConduit to CenterStud on YokeStud on Yoke
Lot 8 2570WLot 8 2570WHoist Unbalance Hoist Unbalance ““As FoundAs Found””485 Amps 485 Amps –– 12.2%12.2%
Lot 8 2570WLot 8 2570WDrag Unbalance Drag Unbalance ““As FoundAs Found””988 Amps 988 Amps –– 24.9%24.9%
Lot 8 2570WLot 8 2570WHoist and Drag Unbalances Hoist and Drag Unbalances ““As LeftAs Left””After Adjustments and Making Both Motions into Two LoopsAfter Adjustments and Making Both Motions into Two LoopsHoist Unbalance 53 Amps Hoist Unbalance 53 Amps –– 1.3% Drag Unbalance 95 Amps 1.3% Drag Unbalance 95 Amps –– 2.4%2.4%
Key 2 8750Key 2 8750Drag Unbalance Drag Unbalance ““As FoundAs Found””1800 Amps 1800 Amps –– 50%50%
Key 2 8750Key 2 8750Drag Unbalance Drag Unbalance ““As LeftAs Left””59 Amps 59 Amps –– 1.6%1.6%
Key 2 8750Key 2 8750Hoist Unbalance Hoist Unbalance ““As FoundAs Found””616 Amps 616 Amps --15.6%15.6%
Key 2 8750 Key 2 8750 Hoist Loop Unbalance Hoist Loop Unbalance ““As LeftAs Left””139 Amps 139 Amps –– 3.5%3.5%
Related WMEA Papers Related WMEA Papers –– available on available on wmea.netwmea.net
•• National Carbon National Carbon –– Successful Brush Successful Brush Performance Performance –– Jun 05Jun 05
•• NECP NECP –– Tuning DC Motors and Tuning DC Motors and Generators Generators –– Jun 07Jun 07
Reference MaterialsReference Materials
• “Loop Unbalance Guidelines” – GE Benchmark, January 1997, Steve Baade
• “Loop Unbalance Guidelines” – GE Benchmark, April 1997, Steve Baade
• GE “DC Machine Adjustments and Operating Characteristics”
Reference Web SitesReference Web Sites
•• Morgan AM&T Morgan AM&T –– National Electrical National Electrical Carbon Carbon –– www.morganAMT.comwww.morganAMT.com
•• GE Motors GE Motors -- www.GEMotors.comwww.GEMotors.com