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Testing Procedure for Shaft

Voltage and Discharges

using a Fluke ScopeMeter

SVP

S H A F T V O L T A G E P R O B E

www.est-aegis.com


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2014 - Electro Static Technology Patented Technology1 www.est-aegis.com

Table of Contents and Safety

Page

Where to purchase AEGIS products 2

Why test for shaft voltages 3

Electric motor design 4-5

Voltage arcing through bearing 6

Recommended testing equipment 7

Installing AEGIS SVP Tip 8

Setting ScopeMeterparameters 9-18

Taking the measurements 19-21

Examples of shaft voltage readings 22-24

Saving images 25

Creating test reports 26

AEGIS SVP Tip specification 27-28

AEGIS Shaft Grounding Ring best practices 29-33

Conclusion 34

Always wear safety glasses.

Power down the motor, install testingequipment and restart motor

Use the magnetic base when takingshaft voltage readings

Ensure all wires are away from rotatingequipment

SAFETY


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Patented Technology 2014 - Electro Static Technology 2www.est-aegis.com

Where to Purchase AEGIS Products

AEGIS Shaft Grounding Products are sold through distribution. Please visit our

website for a distributor in your area. www.est-aegis.com

AEGIS SGR Bearing Protection Rings

AEGIS SVP

Shaft Voltage Kit

For a complete guide to shaft grounding bestpractices, shaft voltage testing, and bearinginspections, download the AEGIS Handbookat www.est-aegis.com/handbook


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Why Test for Shaft Voltages...

Unexpected production down time due to afailed motor is costly.

Air conditioning failure in a commercial buildingis unacceptable.

A stopped train during rush hour is avoidable.

...because bearing failures are costly

Typical Bearing Failure Cost:Small Motor10 HP/215T

Large Motor300 HP/449T

Rigging/Removal and Replacement $1,000 $2,000

Motor Repair $990 $13,200

Production Downtime $10,000 $100,000

Total $11,990 $115,200

Cost of AEGIS installed on Marathon motorto Prevent Bearing Fluting Failure

$456 $1,327

Return on Investment 2629% 8681%


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Electric Motor Design

460 VAC

60Hz

Electric induction motors are designed for operation on 3 phase sine wave power

- either 50 or 60 Hz.The input power is balanced in frequency, phase (120 degrees apart) and inamplitude.

Common mode voltage - the sum of the 3 phases always equal zero volts whenproperly balanced.

Note: Bearing protection generally not needed except for large frame motors.

Electric Motor Operated by Variable Frequency Drives (VFD)

When operated by VFD, the power to the motor is a series of positive and negativepulses instead of a smooth sine wave.

The input voltage is never balanced because the voltage is either 0 volts, positive,or negative with rapid switching between pulses in all three phases.

The common mode voltage is usually a square wave or 6 step voltage waveform.

Electric Motors Operating on Line Voltage

Balanced

vo

ltagecondition

Unbalanced

voltagecondition


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An Electric Motor looks like a Capacitor

The pulses to the motor from the VFD create a capacitively

coupled common mode voltage on the motor shaft.

The voltage looks for a path to ground and breaks down thedielectric in the bearing.

The resulting discharge through the motor bearing creates apit in the bearing race and over time the bearing fails.


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Voltages arc through the bearings,

and electrical discharge machining(EDM) creates thousands of pits

Bearings degrade, resulting inincreased friction and noise

Eventually, the rolling elements cancause fluting damage to bearing

races

Bearing lubrication/greasedeteriorates, is burnt and fails

Potential for costly unplanneddowntime

Voltage arcs through the bearing

FROSTING

EDM PIT

FLUTING

Burnt Grease


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Recommended Testing Equipment

Oscilloscope with a 10:1 probe. We

recommend a minimum 100MHzbandwidth to accurately measurethe waveform. (Fluke 190 SeriesII ScopeMeter 4 channel shown).The Fluke 190 Series II ScopeMeter2 channel also has an ohmmeterfunction which can be used tomeasure the resistivity of the shaft.

Magnetic base tofit the 3/8 (9.5mm)probe extensionrod.

AEGIS Simulator

- used to simulatean AEGIS ShaftGrounding Ringon shaft.

AEGIS SVP ShaftVoltage Probe Kit


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AEGIS SVP Tip Installation

Fluke VPS410 10:1 probe

1. Remove the protective cap 2. Remove the plastic sleeve 3. Probe with sleeve removed

4. Attach ground lead 5. Install the AEGIS SVP tip overthe probe tip

6. Secure the tip to the probeusing the thumb screw. Be carefulnot to over tighten.


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Setting the ScopeMeter Parameters

The following pages describethe parameters we use to capture

shaft voltages. Although not allmeters have the same options,the basic concept is the same.

To demonstrate, we will use theFluke 190-204 ScopeMeter4 channel - 200 MHz.

Connect 10:1 probein Input A


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Press theAbutton for channel A.Menu will appear at the bottom.

Press SCOPE

Press F1to toggle ON

Press SCOPEto clear menu

ScopeMeter ParametersSet Readings ON

Instructions are specific to the Fluke 190-204 ScopeMeter. Refer toyour owners manual for a different meter.

Use the toggle keys in the middle to toggle through the menu.Always press the ENTER button to confirm your actions.


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Press F2 COUPLING to togglebetween the DC and ACCoupling.

Choose DCand press ENTER.

Press CLEARto clear menu.

Press theAbutton for channel A.Menu will appear at the bottom.

DC Coupling will pick up DCand AC voltages.

ScopeMeter ParametersDC Coupling


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Press F2 READING. Cursorto desired channel and pressENTER.

Press the SCOPEbutton. Amenu will appear at thebottom.

Use up/down arrows tochoose Peakand pressENTER.

ScopeMeter ParametersSet Voltage Peak-Peak


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Press CLEARto remove themenu bar.

Choose Peak to Peakandpress ENTER.

Voltage Peak to Peakis nowset.

ScopeMeter ParametersSet Voltage Peak-Peak


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Press F4 INPUT A OPTIONS.Press A button. Menu willappear at the bottom.

Column 1 choose Normalandpress ENTER.

Column 2 choose Fullandpress ENTER.

Press CLEARto clear themenu.

ScopeMeter ParametersSet Polarity and Bandwidth


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Move cursor to 3rd column

Averages: OFF

PressENTER

To show specific voltagemeasurements instead ofaverages:

Press the SCOPEbutton.

Press F4 WAVEFORMOPTIONS

In column 4

Waveform: Normal

Press ENTER

Press CLEARto clear themenu

Set Waveform Averages OFFScopeMeter Parameters and Waveform Normal


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In this example the amplitude istoo small. Increase RANGE(mV)to show more detail.

Amplitude will need to beadjusted according to theconditions.

Set to show completesine wave from top peakto bottom peak using theRANGEbutton.

In this example the amplitudeis too large. DecreaseRANGE(V) to show top andbottom peaks.

ScopeMeter ParametersSet Voltage Amplitude


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ScopeMeter ParametersSet Amplitude

An EDM discharge pattern will show a climb in voltage and then a sharp vertical

line. The sharp vertical line shows the moment of discharge to ground. Each

motor will have its own unique parameters.

Control the vertical span of the displayed signal by adjusting the volts per

division. The signal peak to peak should all be displayed on the screen. 5V is a

good place to start and then adjust based on the conditions.

Press mV to increase vertical sensitivity

Press V to decrease vertical sensitivity

This is an example of amplitude set to 5

volts per division. The trace is clearly shown.

If the peak extends beyond the screen,

decrease the amplitude.


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ScopeMeter ParametersSet Time Period

Control the horizontal span of the displayed signal by adjusting the Time.

400s (microseconds) is a good place to start and then adjust TIME based on

the conditions.

Press ns to increase horizontal sensitivity

Press s to decrease horizontal sensitivity

This is an example of a Time

period set to 4 microseconds

(4/1,000,000). It clearly shows a

climb in voltage and a sharp

discharge to ground.


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Taking the Measurements

Ground Reference Reading: EMI

1. The reading displays ground noise or EMI beingproduced by the motor/drive system. This electri-cal noise may be present before and after install-ing the AEGIS ring.

2. Find 2 ground points on the motor. Must be baremetal and conductive.

3. Place the SVP on one of the points and the probe

grounding clip on the other point.

4. Measurements will vary depending on the motorsize and conditions.

1. Shaft must be clean & free of any coatings, paintor other nonconductive material.

2. Secure the probe in place with magnetic base.

3. Align AEGIS SVP on shaft end or side ensuringcontinuous contact. Avoid keyway if possible.

4. Place oscilloscope grounding lead on bare metalof motor ensuring conductive path to ground.

5. If you plan to create a report for the customer,save the image.

Follow all safety precaution when workingwith rotating equipment.

Shaft Voltage Reading


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Taking the Measurements Using the Simulator

First Take the Shaft Voltage Reading

without Shaft Grounding1. Shaft must be clean & free of any coatings, paint

or other nonconductive material.

2. Secure the probe in place with magnetic base.

3. Align AEGIS SVP on shaft end or side ensuringcontinuous contact. Avoid keyway if possible.

4. Place oscilloscope grounding lead on bare metalof motor ensuring conductive path to ground.

5. Save the image. Please refer to page 25 for thisaction.

The voltage measurement of 31.2V peak to peak isan example of the voltage discharging through thebearings without AEGIS shaft grounding.

Follow all safety precaution when workingwith rotating equipment.


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Measurements Using the AEGIS Grounding Simulator

Next Take the Shaft Voltage Reading

with the Simulator Grounding theShaft

1. Maintain the same setup as in the previous page.

2. Place AEGIS Grounding Simulator groundinglead on bare metal of motor ensuring conductivepath to ground.

3. Place the Simulator against the shaft to simulatethe AEGIS SGR Bearing Protection Ring.

4. Save the image.

The voltage measurement of 1.2V peak to peak isan example of the voltage discharging throughthe Simulator to ground. The AEGIS SGR BearingProtection Ring will perform equally or better.

AEGIS GroundingSimulator


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Typically 20 to 120 volts peak to peak. The waveformimage shows the capacitive coupled common modevoltage on the shaft of the motor. The six-stepwave form is the result of the 3 phases of pulses fromthe VFD. The timing of the pulse width modulation

(PWM) pulses to the motor from the drive determineswhat the wave form looks like. Sometimes it will looklike a square wave.

This six-step or square wave is what is seen whenthere is no bearing discharge and the peak to peakshaft voltage is at its maximum level. The voltagelevel may eventually overcome the dielectric in mostnon-isolated bearings and begin discharging.

Examples of Shaft Voltage Readings

High Peak to Peak common modevoltage

Typically EDM discharges can occur from 6 voltspeak to 80 volts peak depending on the motor, thetype of bearing, the age of the bearing, and otherfactors. The waveform image shows an increasein voltage on the shaft and then a sharp verticalline indicating a voltage discharge. This can occurthousands of times in a second, based on thecarrier frequency of the drive. The sharp verticaldischarge at the trailing edge of the voltage is anultra high frequency dv/dt with a typical dischargefrequency of 1 to 125 MHz (based on testing

results in many applications).

High amplitude EDM discharge

pattern

The use of cursors is handy to determine

voltages at a specific spot in the reading.


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Even though the voltage peak to peak waveformshows a small change (3.2V pk-pk in this case) thebearing is still experiencing arcing thousands oftimes in a second.


Low amplitude EDM dischargepattern

Typically the peak to peak voltages are 4 to 15 voltspeak to peak. The waveform image shows a morecontinuous discharge pattern with lower dv/dtfrequencies between 30 KHz to 1 MHz. The lowervoltage is due to greater current flow in the bearings

which is the result of the bearing lubricationbecoming conductive. As discharges occur in thebearings, the lubrication is contaminated withcarbon and metal particles. The lower impedanceto the shaft voltages results in lower peak to peakvoltages. This condition is usually found in motorsthat have been in operation for many months oryears.

Low amplitude voltage dischargepattern


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With the AEGIS ring installed, you will typicallysee discharge voltage peaks around 2 to 3 voltson a bare steel shaft surface. The voltage readingsmay be decreased with the application of AEGISColloidal Silver Shaft Coating which allows for a

more efficient electron transfer to the conductivemicro fiber tips. The waveform image shows thelow peak to peak waveform of a motor with theAEGIS SGR ring installed and discharging the shaftvoltages.


Peak to Peak voltage with AEGISring installed

Typical Bearing Greasenew grease vs burnt greaseAEGIS bearing protection also helps maintain the

quality of the motor bearing grease. Continuouselectrical arcing in the motor bearings will oftenrapidly deteriorate the quality of the grease andcause bearing race damage. When an arc occurs,

the grease is superheated and causes the greaseto break-down. In addition to the burnt grease,the arcing causes small metal particles to loosenfrom the bearing races/balls which then dispersethrough the grease.

Bearing Grease


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ScopeMeter Saving Images as .BMP on USB

1. Plug in a USB drive

2. Saving images as .BMP allow you to viewyour file without using the Fluke softwareon your computer.

3. You will not be able to change the filename as you are saving it but you canchange it later.

4. Hold Image on screen

5. Save

6. F1 Save

7. F1 again to change from INT to USB (this isnot saving the file)

8. F4 Close

9. F3 to save to USB

10. Press Clear to Clear menu

11. To view USB saved files, use a computer.


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Shaft Voltage Test Reports

Shaft Voltage Test Report:

Measuring the shaft voltage on VFD driven motorsprovides the end user with valuable information todetermine if there is a potential risk of bearingdamage from electrical bearing discharges.

Surveying and documenting shaft voltage readingsand wave forms will assist in determining theappropriate mitigation or solution.

Note: The best time for shaft voltage measurementsare during initial start-up in new or repaired motorsoperated by the VFD. Shaft voltage measurementsshould be incorporated into preventive andpredictive maintenance programs and may be

combined with vibration analysis, thermography orother services.

Report template available at: www.est-aegis.com/bearing


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SVP Tip Specifications

The AEGIS SVP-KIT-3000MB, SVP-KIT-3000 andSVP-TIP-3000 are designed to fit the following

Fluke 10:1 voltage probes:

Fluke VPS200

Fluke VPS410

Tips for other probe styles are available. Seewebsite for details. www.est-aegis.com

0.157 (4mm)

1.317 (33.45mm)Must be a 1.200 (30.48mm) min

0.242

(6.15mm)

2.100 .010

0.680

.005

Conductive

micro fiber 6-32 thumb

screw

Probe

SVP Tip


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AEGIS SVP Shaft Voltage Probes

The AEGIS SVP-KIT-3000 includes 3 SVP tips, probeholder with two piece extension rod (total length ofprobe holder with extension rod is 18 inches), andAEGIS Grounding Simulator. Fits 3/8 magnetic base(base not included).

The AEGIS SVP-TIP-3000 includes 3 SVP tips only.

The AEGIS Grounding Simulator is used to demonstratethe AEGIS SGR Shaft Grounding Ring function bygrounding the rotating shaft of the motor with theconductive microfibers of the AEGIS GroundingSimulator.

The AEGIS SVP-KIT-3000MB includes 3 SVP tips, probeholder with two piece extension rod (total length ofprobe holder with extension rod is 18 inches), AEGISGrounding Simulator, and magnetic base.

SVP-KIT-3000

SVP-TIP-3000

SVP-KIT-3000MB


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AEGIS Shaft Grounding Ring Best Practices

Damaging shaft voltages

can cause bearing failure.

SOLUTION:

Install an AEGIS Shaft GroundingRing to protect motor bearings from

harmful shaft voltages.


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Voltage Reading Comparison

SHAFT VOLTAGE READING

WITHOUT AEGIS SGR Shaft

Grounding:

SHAFT VOLTAGE READING

WITH AEGIS SGR Shaft

Grounding:

Readings taken on a conveyor motor

PROBLEM SOLUTION


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BEST PRACTICES FOR SHAFT GROUNDING MITIGATION

-Motors up to and including 100 HP (75 kW) -Low Voltage

The AEGIS SGR Shaft Grounding Ring will safely channel harmful shaft voltages awayfrom the bearings to ground.

Internal or external

installation

General recommendations: For induction motorseither foot mounted, c-face or d-flange mountedmotors with single row radial ball bearings on bothends of the motor. Motors may be installed eitherhorizontally or vertically in the customers

application.

Install one AEGIS SGR Bearing ProtectionRing on either the drive end or the non-driveend of the motor to discharge capacitiveinduced shaft voltage.

AEGIS SGR may be installed eitherinternally or externally.

Use AEGIS Colloidal Silver Shaft Coating(PN# CS015) on motor shaft where fiberstouch.

Product recommendation: AEGIS SGR

Follow all safety precautions.MSDS available for download atwww.est-aegis.com


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BEST PRACTICES FOR SHAFT GROUNDING MITIGATION-Motors Greater than 100 HP (75 kW)

For horizontally mounted motors with single rowradial ball bearings on both ends of the motor:

Non-Drive end: Bearing housing must beisolated with insulated sleeve or coating or

use insulated ceramic or hybrid bearing todisrupt circulating currents.

Drive end: Install one AEGIS BearingProtection Ring .

AEGIS Ring can be installed internally onthe back of the bearing cap or externally onthe motor end bracket.

Use AEGIS Colloidal Silver Shaft Coating(PN# CS015) on motor shaft where fiberstouch.

Product recommendation: Low Voltage Motors up to 500HP:

AEGIS SGR

Low Voltage Motors over 500HP:AEGISiPRO

Medium Voltage Motors:AEGIS iPRO

sleeve

Install AEGIS Ring on opposite end of insulation

For more options, download our AEGIS Handbook at

www.est-aegis.com/handbook


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Typical Installations on a Motor

AEGIS uKIT AEGIS uKIT

AEGIS SGR solid ring withconductive epoxy.

AEGIS SGR split ring withconductive epoxy.


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Conclusions

VFD driven motors have shaft voltages that may discharge in themotor bearings.

Bearing discharges cause pitting and fluting damage andcatastrophic bearing failure.

Protecting motor bearings is essential in ensuring reliability and highup-time.

AEGIS Simulator will demonstrate shaft grounding to protectbearings.

Add AEGIS Bearing Protection to improve reliability by providing aless resistant path to earth ground.

This procedures manual is intended as a general guidance to assist with proper testing and application ofthe AEGIS SGR Bearing Protection Ring to protect motor bearings. All statements and technical informationcontained in this procedures manual are rendered in good faith. User must assume responsibility to determinesuitability of the product for its intended use. The manufacturer shall not be liable for any injury, loss or damage,direct or consequential arising out of the use, or attempt to use the product.

h i l S


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Technical Support

The AEGIS website contains the latest productliterature and installation guidelines.

United States

Telephone Email

1.866.738.1857 [email protected]

World Wide Web

www.est-aegis.com

Version 2.0

January 1, 2014

Copyright 2014 Electro Static Technology-an ITW Company. All rights reserved. AEGIS and the AEGIS logo are

registered trademarks of Electro Static Technology in the United States and other countries. Other trademarks are the

property of their respective owners. Product specification, size and shape are subject to change without notice, and

actual product appearance may differ from that depicted on the packaging. Visit www.est-aegis.com for more details.

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