NECP--Tuning DC Motors and Generators.pdf

Tuning Up DC Motors and Tuning Up DC Motors and Generators for Commutation Generators for Commutation

and Performanceand Performance

Rich HallRich Hall-- National Electrical CarbonNational Electrical CarbonWestern Mining Electrical Western Mining Electrical

AssociationAssociationJune 8, 2007, Billings MontanaJune 8, 2007, Billings Montana

Sometimes your machine may not Sometimes your machine may not run just like it shouldrun just like it should

That is an indication That is an indication that it might be time for that it might be time for

a a ““tunetune--upup””

Spark PlugsSpark Plugs Breaker PointsBreaker Points

CondenserCondenser RotorRotor

Distributor CapDistributor Cap

Spark Plug WiresSpark Plug Wires

But even with all new But even with all new parts, the machine may parts, the machine may

not run right!not run right!

UnlessUnless you make the you make the ““tunetune--upup”” adjustments!!adjustments!!

That That includes includes setting setting

the the spark spark plug plug

gap, the gap, the ignition ignition

point point gap or gap or dwell, dwell,

and the and the ignition ignition timingtiming

DC machines need tuneDC machines need tune--up adjustments to run up adjustments to run

properly, too!properly, too!

DC machines tuneDC machines tune--up up adjustments to run adjustments to run

properly, too!properly, too!

These adjustments include These adjustments include setting neutral and adjusting setting neutral and adjusting

the commutating field the commutating field ((interpoleinterpole) strength.) strength.

Electrical Neutral MethodsElectrical Neutral Methods

•• Black BandBlack Band•• Kick Inductive NeutralKick Inductive Neutral•• AC NeutralAC Neutral•• Speed ReversibilitySpeed Reversibility•• DC Current In ArmatureDC Current In Armature•• Pencil Volt NeutralPencil Volt Neutral•• Tram Markings/Mechanical MethodTram Markings/Mechanical Method

Electrical Neutral MethodsElectrical Neutral Methods

•• Also see Also see ““Setting Neutral by AC Setting Neutral by AC Curve Method for DC MachinesCurve Method for DC Machines”” by by Rick Scherer, Flanders, WMEA, Rick Scherer, Flanders, WMEA, November 2005 (WMEA Web Site, November 2005 (WMEA Web Site, www.wmea.netwww.wmea.net))

Electrical NeutralElectrical NeutralSetting Neutral on an electric motor or Setting Neutral on an electric motor or generator is similar to setting timing generator is similar to setting timing on an engine.on an engine.

The brushes are basically electricallyThe brushes are basically electricallypositioned on the commutator betweenpositioned on the commutator betweenthe areas of main pole flux so commutationthe areas of main pole flux so commutationcan take place at the right time and in ancan take place at the right time and in anarea where no electrical work ( torque ) isarea where no electrical work ( torque ) isbeing produced.being produced.

NeutralNeutralUsually it is best to look for Usually it is best to look for ““factory markfactory mark””and set brush yoke to this position after and set brush yoke to this position after reassembling the motor.reassembling the motor.

The OEM has the benefit of knowing the The OEM has the benefit of knowing the electrical design and how previous motors electrical design and how previous motors were adjusted. They also have more test were adjusted. They also have more test equipment than the typical motor repair equipment than the typical motor repair shop, for running the motor under load at shop, for running the motor under load at various speeds.various speeds.

Factory Neutral MarkFactory Neutral Mark

Shifted off the factory markShifted off the factory mark

If armature has been changed, or brush If armature has been changed, or brush arms moved on yoke, correct setting may arms moved on yoke, correct setting may not be on not be on ““factory markfactory mark””..

Methods For AdjustingMethods For Adjusting

DC Machines DC Machines

AdjustmentsAdjustments

1. Brush Position1. Brush Position

2. Commutating Field Strength2. Commutating Field Strength

Factory MethodFactory Method

Field MethodField Method

Excavator MG SetExcavator MG Set

Black BandBlack Band

A test where you intentionally misadjustA test where you intentionally misadjustthe magnetic strength of the magnetic strength of interpoleinterpole( ( commcomm field ) by adding or subtractingfield ) by adding or subtractingcurrent to find the limits of sparking.current to find the limits of sparking.

Also use this data to adjust neutral settingAlso use this data to adjust neutral settingand and interpoleinterpole shimming for good shimming for good commutation over the range of speedscommutation over the range of speedsand loads.and loads.


•• ProcedureProcedure–– Connect buckConnect buck--boost power supply (low boost power supply (low

Voltage high current) in parallel with the Voltage high current) in parallel with the commutating fieldscommutating fields

–– Operate the machine at various loads (0% to Operate the machine at various loads (0% to 150%), apply buck150%), apply buck--boost current and observe boost current and observe sparkingsparking

–– Adjust brush rigging position or shim Adjust brush rigging position or shim commutating poles as shown from recorded commutating poles as shown from recorded and plotted dataand plotted data

DC Machine and LoadDC Machine and Load

ARMARM LoadLoad

CommCommFieldField

FieldField

Black Band Set UpBlack Band Set Up

ARMARM LoadLoad

CommCommFieldField

FieldField

Buck Boost GenBuck Boost Gen

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

5050 100100 150150

No LoadNo Load

ARMARM LoadLoad

CommCommFieldField

FieldField


IIA A = 0= 0

No Load BoostNo Load Boost

ARMARM LoadLoad

CommCommFieldField

FieldField


IIA A = 0= 0

ii

ii

No Load BuckNo Load Buck

ARMARM LoadLoad

CommCommFieldField

FieldField


IIA A = 0= 0

ii

ii

Buc

k A

mps

Buc

k A

mps

Boo

st A

mps

Boo

st A

mps

00



XX

XX

5050 100100 150150

Band at No LoadBand at No Load

Buc

k A

mps

Buc

k A

mps

Boo

st A

mps

Boo

st A

mps

00



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



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



XX

XX

5050 100100 150150XX

No Load Band No Load Band CenteredCentered

OK OK –– Proceed with load Proceed with load testtest

Loaded BoostLoaded Boost

ARMARM LoadLoad

CommCommFieldField

FieldField


IIA A

ii

IIAA + i+ i

IIAA

Loaded BuckLoaded Buck

ARMARM LoadLoad

CommCommFieldField

FieldField


IIA A

ii

IIAA -- ii

IIAA

Buc

k A

mps

Buc

k A

mps

Boo

st A

mps

Boo

st A

mps

00



XX

XX

5050 100100 150150

xx

xx

Take data with machine Take data with machine loaded, beginning at 50% loaded, beginning at 50% loadload

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

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


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

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

xx

Near perfect black band Near perfect black band ––centered at centered at all loadsall loads


• Advantages– Adjusts both neutral and commutating

pole shimming– Tests over complete load range or can

adjust for specific load and speed

Black BandBlack Band• Advantages

– Adjusts both neutral and commutating pole shimming– Tests over complete load range or can adjust for specific load

and speed

• Disadvantages– Requires field supply and armature

supply capable of 1.5 to 2 times rated armature Amperes

– Need control of loading, voltages, speeds,etc.

– Need buck-boost power supply (low voltage and high current)

Kick Inductive NeutralKick Inductive Neutral

•• ProcedureProcedure–– Connect an analog DC voltmeter Connect an analog DC voltmeter

between shunts of brushes on adjacent between shunts of brushes on adjacent arms (brushes need to be well seated)arms (brushes need to be well seated)

–– Repeatedly apply and remove DC Repeatedly apply and remove DC voltage from shunt fieldsvoltage from shunt fields

–– Shift brush yoke for minimum deflection Shift brush yoke for minimum deflection (kick) if meter needle (kick) if meter needle

++

--

SwitchSwitch

A1A1

A2A2

AnalogAnalog DC VoltmeterDC Voltmeter00

++--

Shift brushes for minimum needle deflectionShift brushes for minimum needle deflection

Shunt Shunt FieldField

Kick Inductive NeutralKick Inductive Neutral

•• AdvantagesAdvantages–– Static TestStatic Test–– Little equipment requiredLittle equipment required

Kick Inductive NeutralKick Inductive Neutral•• AdvantagesAdvantages

–– Static TestStatic Test–– Little equipment requiredLittle equipment required

•• DisadvantagesDisadvantages–– Best compromise neutral for reversible Best compromise neutral for reversible

machines. Best for motors that could machines. Best for motors that could run either rotation.run either rotation.

AC NeutralAC Neutral•• ProcedureProcedure–– Connect an AC voltmeter between the Connect an AC voltmeter between the

shunts of brushes of adjacent arms shunts of brushes of adjacent arms (brushes well seated)(brushes well seated)

–– Apply 120 Volt AC to the shunt fields, Apply 120 Volt AC to the shunt fields, connected where the DC field supply connected where the DC field supply would normally connectwould normally connect

–– Shift the brush yoke to get minimum AC Shift the brush yoke to get minimum AC voltage on the voltmetervoltage on the voltmeter

A1A1

A2A2

Analog or Digital AC VoltmeterAnalog or Digital AC Voltmeter00

120 120 VoltVoltACAC

Shift brushes for minimum AC VoltageShift brushes for minimum AC Voltage

Shunt Shunt FieldField

AC NeutralAC Neutral

•• AdvantagesAdvantages–– Static testStatic test–– Little equipment requiredLittle equipment required

AC NeutralAC Neutral•• AdvantagesAdvantages

–– Static testStatic test–– Little equipment requiredLittle equipment required

•• DisadvantagesDisadvantages–– Best compromise neutral for reversible Best compromise neutral for reversible

machines. Not as good for single rotation machines. Not as good for single rotation machines. Really only gets you in the ball park machines. Really only gets you in the ball park for large machines with pole face windings.for large machines with pole face windings.

Speed ReversibilitySpeed Reversibility

•• ProcedureProcedure–– Apply known DC field Apply known DC field currentcurrent–– Apply known DC armature Apply known DC armature voltagevoltage–– Measure rotational speed (RPM)Measure rotational speed (RPM)–– Keep field Keep field currentcurrent the same, but reverse the the same, but reverse the

armature armature voltagevoltage polarity and measure RPMpolarity and measure RPM–– Shift brush yoke as required to equalize speed Shift brush yoke as required to equalize speed

in both directions within 1%in both directions within 1%

A1A1

A2A2

DC VoltmeterDC Voltmeter

DC DC Power Power SupplySupply

DC DC Field Field

SupplySupply

00

DC AmmeterDC Ammeter

VVAA

IIff

RPMRPM

0

Set ISet Iff, Set V, Set VA, Measure RPM. Reverse Polarity of VA. Measure RPM. Shift until RPMs agee within 1%.

Speed ReversibilitySpeed Reversibility

•• AdvantagesAdvantages–– Good technique for reversible machinesGood technique for reversible machines–– Armature supply does not need to supply very Armature supply does not need to supply very

much currentmuch current

Speed ReversibilitySpeed Reversibility•• AdvantagesAdvantages

–– Good technique for reversible machinesGood technique for reversible machines–– Armature supply does not need to supply very much currentArmature supply does not need to supply very much current

•• DisadvantagesDisadvantages–– Requires both field and armature DC supplyRequires both field and armature DC supply–– Machine must be uncoupled or able to rotate Machine must be uncoupled or able to rotate

unloaded or with controlled loadunloaded or with controlled load–– Best compromise neutral for reversible Best compromise neutral for reversible

machines. Best for motors that could run machines. Best for motors that could run either rotation.either rotation.

•• ProcedureProcedure–– Apply DC current through armature and Apply DC current through armature and

commutation fields onlycommutation fields only–– If on neutral, machine will not rotate. If off If on neutral, machine will not rotate. If off

neutral, machine will rotate in one direction or neutral, machine will rotate in one direction or the other depending on which way it is off the other depending on which way it is off neutralneutral

–– Shift brush yoke as required so motor does Shift brush yoke as required so motor does not rotatenot rotate

•• WarningWarning --Do not use this method on Do not use this method on series motors as they will overseries motors as they will over--speed!!speed!!

DC Current In Armature DC Current In Armature CircuitCircuit

DC VoltmeterDC Voltmeter

A1A1

A2A2

DC DC Power Power SupplySupply

VVAA

IIA

CommCommFieldField

Armature Will Not Turn Armature Will Not Turn on Neutralon Neutral

00

•• AdvantagesAdvantages–– Only armature supply is requiredOnly armature supply is required

DC Current In Armature DC Current In Armature Circuit (Shunt Machines Circuit (Shunt Machines

Only)Only)

•• AdvantagesAdvantages–– Only armature supply is requiredOnly armature supply is required

•• DisadvantagesDisadvantages–– Limited to smaller antiLimited to smaller anti--friction bearing friction bearing

machinesmachines–– Limited to shunt machines (series or Limited to shunt machines (series or

compound machines will overcompound machines will over--speed)speed)–– Best compromise neutral for reversible Best compromise neutral for reversible

machines. Best for motors that could run machines. Best for motors that could run either rotation.either rotation.

DC Current In Armature DC Current In Armature Circuit (Shunt Machines Circuit (Shunt Machines

Only)Only)

Pencil Volt NeutralPencil Volt Neutral

•• ProcedureProcedure–– Place special template on the Place special template on the

commutatorcommutator–– Run machine at 100 Volts, no loadRun machine at 100 Volts, no load–– Measure voltage through holes in the Measure voltage through holes in the

template with a special probetemplate with a special probe–– Plot readings on graph paper and adjust Plot readings on graph paper and adjust

yoke accordinglyyoke accordingly

PVN TemplatePVN Template

Installing PVN TemplateInstalling PVN Template

PVN TestPVN TestPointsPoints

PVN PVN AnchoringAnchoring

PointPoint

PVN VoltmeterPVN Voltmeter


RotationRotation

VoltmeterVoltmeter

Pencil Pencil ProbeProbe

Brush StudBrush Stud

Brush Brush BoxBoxTemplateTemplate

Warning!!Warning!!Working around rotating electrical machineryWorking around rotating electrical machinery

can cause serious or fatal injury due to can cause serious or fatal injury due to electrical shock hazards or contact with electrical shock hazards or contact with

rotating parts. Contact the manufacturerrotating parts. Contact the manufacturer’’s s service engineers for performing adjustmentsservice engineers for performing adjustmentson electrical motors and generators. These on electrical motors and generators. These

people have the necessary training and people have the necessary training and information available to properly adjustinginformation available to properly adjusting

DC machines.DC machines.

Typical DataTypical Data

Pencil Volt NeutralPencil Volt Neutral836 KW Generator836 KW GeneratorTaken at 100 volts Taken at 100 volts -- No LoadNo Load

Lead VoltageLead Voltage Trail VoltageTrail VoltageHole No.Hole No.19.919.9

21.521.5

23.323.3

25.025.0

26.826.8

16.416.4

17.917.9

19.619.6

21.321.3

23.023.0

44

55

66

77

88

Note: Lead Volts Higher Than Trail Volts For SingleNote: Lead Volts Higher Than Trail Volts For SingleRotation Machine. For a Reversible Machine,Rotation Machine. For a Reversible Machine,Lead Volts Equals Trail Volts.Lead Volts Equals Trail Volts.

Neutral AdjustmentsNeutral Adjustments

•• To lower trail voltsTo lower trail voltsshift brush riggingshift brush riggingagainst rotationagainst rotation

•• To raise trail voltsTo raise trail voltsshift brush riggingshift brush riggingwith rotationwith rotation

•• To raise trail voltsTo raise trail voltsshift brush riggingshift brush riggingagainst rotationagainst rotation

•• To lower trail voltsTo lower trail voltsshift brush riggingshift brush riggingwith rotationwith rotation

GeneratorGenerator MotorMotor


•• AdvantagesAdvantages–– Repeatable, accurate way to set neutralRepeatable, accurate way to set neutral–– Can adjust single rotation machinesCan adjust single rotation machines

Pencil Volt NeutralPencil Volt Neutral•• AdvantagesAdvantages

–– Repeatable, accurate way to set neutralRepeatable, accurate way to set neutral–– Can adjust single rotation machinesCan adjust single rotation machines

•• DisadvantagesDisadvantages–– Requires working closely with energized Requires working closely with energized

rotating machineryrotating machinery–– Motors must be mechanically uncoupled or Motors must be mechanically uncoupled or

able to operate with little loadable to operate with little load

Other Methods Of Setting Other Methods Of Setting NeutralNeutral

There are other methods of setting neutral. There are other methods of setting neutral. It is important that neutral be set by It is important that neutral be set by somesomemethod as commutation or motor or method as commutation or motor or generator performance may suffer.generator performance may suffer.

Using Static Neutral Setting Using Static Neutral Setting Methods for Single Rotation Methods for Single Rotation

MachinesMachines

From experience, excavator generators From experience, excavator generators can be shifted about can be shifted about ½½ bar against bar against

rotation from symmetrical neutral to rotation from symmetrical neutral to approximate black band or pencil Volt approximate black band or pencil Volt

neutralneutral

Adjusting Commutating Adjusting Commutating Field (Field (InterpoleInterpole) Strength) Strength

Adjusting Adjusting commcomm field strength in the field is field strength in the field is difficult to impossible. difficult to impossible.

The machine voltage, speed and load must The machine voltage, speed and load must be controlled, which is usually impossible, be controlled, which is usually impossible, and some of the methods available, such as and some of the methods available, such as brush potential measurements, have safety brush potential measurements, have safety issues. issues.

Adjusting Commutating Adjusting Commutating Field (Field (InterpoleInterpole) Strength) Strength

Some manufacturers ( GE ) use nonSome manufacturers ( GE ) use non--magnetic magnetic interpoleinterpole bolts. These can be bolts. These can be same size as main pole bolts. Do Not mix same size as main pole bolts. Do Not mix these up. Look at bolt head markings. these up. Look at bolt head markings. Magnetic bolts will have 3 (grade 5) or 6 Magnetic bolts will have 3 (grade 5) or 6 (grade 8) radial marks.(grade 8) radial marks.

The order of the shims is also important,The order of the shims is also important,make sure to put them back like youmake sure to put them back like youfound them! Best to put tape around thefound them! Best to put tape around thewhole whole ““shim packshim pack”” and mark similar to:and mark similar to:4 o4 o’’clock pole this side toward frame IDclock pole this side toward frame ID

Properly adjusting DC Properly adjusting DC machines not only affects machines not only affects

commutation, but also commutation, but also machine performance and machine performance and

loop balanceloop balance

Properly maintained, the Properly maintained, the electrical equipment electrical equipment

used in mining used in mining machinery can perform machinery can perform

well for many, many well for many, many years.years.

And it will not end up And it will not end up like like thisthis pair!!pair!!

Rich HallRich Hall

Old broken down excavator and Old broken down excavator and old broken down engineerold broken down engineer

NECP--Tuning DC Motors and Generators.pdf

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