SERVING Industry SINCE 1923
And Our Partnership Team providing Inspection ,
Testing , & Repair of Generators, Turbines, & Stators
Generator Testing & Inspection
Generator Services
• Field Services
• Stator Services
• Testing & Inspections
• Hydraulic Integrity Test (HIT)
• Liquid-Cooled Clip Repairs
• High Voltage Bushings
• Reverse Engineering
Generator Field Services
Turnkey Rewinds
Technical Direction
Retaining Ring Change Outs Using Induction
Heating
Retaining Ring Machining & Insulation
Repairs of Elongation, Foreshortening & Top
Turn Isolation
Main Lead Manufacturing
Containment Facilities & Asbestos Abatement
Copper Dust Inspections
Bore Copper Inspection & Replacement
NDE of Wedges, Forging & Rings
Hydrogen Seal Inspection
Turnkey Collector Ring Services
Painting of Forgings
Application of Tagging Compounds
Turnkey Transportation
Generator Stator Services
Conventional and Liquid-Cooled Rewinds
Turnkey Disassembly & Assembly
New Stator Bars, Including Liquid-Cooled
Project Management & Technical Direction
Bar Insulation Repair
Repair of core iron
End Winding Redesign & Installation
Re-Wedging & Upgrades, Including TIL-
1197
Tagging Compounds for Core Monitoring
Installation of Flux Probes, Buss & Slot
Couplers
Installation of New RTDs
Electrical Testing & Inspection Services
AC & DC Hi Potential Test
AC Impedance Tests
Digital ELCID
Meggar
Boroscopic Inspections
Pole Balance Drop
Calculation of Polarity Indexes
DC Leakage
Wedge Surveys and Mapping
Resistance Testing of RTDs
Visual Inspections
Capacitance Mapping
Retaining Ring Inspections
H.I.T. Skids / Flush & Bake Skids
For Liquid Cooled Generators
Five Skids
Tools to Address TIL 1098
Fast Dry Out of Cooling System for
Elec. Testing
Prep For Vacuum & Pressure Decay
Tests
Flush & Bake Skids:
Flush Stator Cooling System & Bars
After Rewind
Cures Epoxies & Conforming
Materials
Reduces Bake Cycle Significantly
High Voltage Bushing Refurbishment
New or Refurbished High Voltage
Bushings :
Re-manufacture & rebuild nearly all
models
Refurbishment cost much less than new
bushings
Provides an opportunity to upgrade
bushing components
Faster turn-around than waiting for new
bushings
We maintain a finished inventory of
common bushings
Porcelain or composite insulators
Complete electrical testing
Turnkey installation
Rotor Testing & Inspection
Components of a Field
Collector Rings
Journal
Fan Ring
Retaining Ring
Body
Slot
Blocking
Coils
Coupling
Components of a Field Slot
Wedge
Creepage
Turns
Turn Insulation
Slot Armor
Sub Slot Armor
Typical Electrical Field Test on a Generator Rotor
Megohm Test (megger)
Winding Resistance Test
AC Impedance Test
Pole Balance Test
Visual Inspections
Field Testing
Megohm Test (megger)
Checks Ground Wall Insulation
Slot Liners
Creepage Blocks and Slot Bottom Covers
Retaining Ring Insulation
Terminal Stud Insulation
Bore Copper Tube
Collector Ring Sleeves
Field Winding Resistance Test
Measurement is converted to standard temperature specific to the
manufacturer
Field Winding Resistance Test
Typical Issues to Identify
Lower than Normal Resistance Means
Turn
to Turn Shorting is Present
Higher than Normal Resistance Could
Mean
a Few Different Things:
Cracked Conductor
Elongated Conductors
Bad Connection
Field Testing
AC Impedance Test
Checks for Turn to Turn Shorting
Rotor Acts as an Inductor when
Passing AC
Current Through the Windings
The Current Flow is “Choked” or
Restricted by
the Number of Turns Around the Iron
Core
(Rotor Body)
AC Impedance Test Set
Voltage is raised in 10V steps and current is measured at
each step.
Also, Impedance (Ohms) is calculated
Pole Balance Test
Only Performed if Access is Available to
the Pole to Pole Connector (or Very Close
By)
Usually Performed with AC
Voltage Applied as High as Practical--
Usually 100V
Voltage is Measured from Inboard Collector
Ring to the Pole Jumper and then from the
Field Testing
Field During Rewind
Bore Copper Assembly
Stator Testing
Stator (Armature) Testing
Winding Resistance Test
Megohm Test (megger)
DC Leakage Test
DC Hipot
RTD Resistance Test
RTD Megger Test
Winding Resistance Test
oMeasured with a Digital Low Resistance
Ohm
Meter (DLRO)
• Also Known as a “Bridge”, “Ductor”,
“Micro Ohm Meter”
Regardless of Name, All are a 4 Wire Kelvin
Bridge Device
Stator Field Testing
Stator Field Testing
Megohm Test (megger)
Checks Ground Wall Insulation
Taped Insulation on Bars/Coils
Porcelain or Epoxy Insulation on
Terminal and Stand-off Bushings
Hoses on Water or Oil Cooled
Machines
Stator Field Testing
Megohm Test (megger)
Usually Performed at 2500 V or 5000 V
for 10 Minutes
All Megger Tests are DC
Achieve a Final Megohm Reading and
Polarization Index (PI)
PI = R10 / R1
Stator Field Testing
Megohm Test (megger)
Reduced Creepage Paths (Distance to
Ground) Can Lead to Low Megohm
Readings
Dirty or Contaminated
Bushings/Terminals
Insulation Migration (Big Problem in
Certain Asphalt-Mica Machines)
Stator Field Testing
AEMC Electronic
Megohm Meter
Stator Field Testing
DC Leakage Test
A High Voltage Test of the Stator
Windings Used to Gain Quantitative
and Historical Data as to the
Condition of the Insulation
DC Tests in General are Sensitive
Indicators of the Presence of
Cracks, Fissures, Reduced
Creepage Paths, Moisture and Dirt
Stator Field Testing
DC Leakage Test
Consists of a Series of Insulation
Resistance Measurements Taken at
Increasing Voltage Steps on a
Scheduled Time Basis
A 10 Minute Preliminary Di-electric
Absorption Test Determines the
Absorption Ratio of the Insulation
(N number)
Stator Field Testing
DC Leakage
Test Underway
Stator Field Testing
DC Leakage Test
Sphere-Gap Voltmeter Is Used to
Verify Voltmeter and for Overvoltage
Protection
Sphere-Gap Voltmeter (Spheres) Are
Set to Arc Over at 10 to 15% Higher
Than Max Test Voltage
Set High Enough So That It Does Not
Add Significant Leakage Current
Stator Field Testing
80 KV DC Hipot, Isolation
Transformer and Sphere-Gap
Voltmeter
Stator Field Testing
DC High Potential Test (Hipot)
Final Suitability for Service Test
Substitute for AC Test, Which
Requires a Large and Expensive Piece
of Equipment
May or May Not Be Required by
Insurance Company
Stator Field Testing
DC High Potential Test (Hipot)
Often Times Is Performed as the
Last Step of a DC Leakage Test
Leakage Value Is Not Important
Since Extraneous Leakage Currents
Can Be Very High
Surface Tracking
Ionization of Air Near Terminals
Stator Field Testing
RTD Testing
Resistance Test
Resistance Is Measured
Between Each Leg (wire)
Excel Spread Sheets Calculates
Temperature
Checked to Insure That All
RTDs are Functional
Stator Field Testing
RTD Testing
Megger Test (Slot RTDs Only)
Resistance to Ground Is
Measured at 500 Volts
Checked to Insure That
RTDs are Not Capable of
Creating Circulating
Currents Which Could
Result In Localized Heating
and Back Feeds into the
Meters
Stator Photos
End Windings
and Core on
Large Water
Cooled
Generator
Stator Photos
Stand-Off
Insulator
Stator Photos
PTFE Hoses
on Water
Cooled Stator
Stator Photos
Tape
Separation on
Asphalt-Mica
Bar
Stator Photos
Typical GE RTD
Panel
Turbine-Generator Repair Facility
• 170, 000 Square Feet
• 90 Ton Crane Capacity
• Dedicated Blast Cleaning
• High Speed Balance Facility
(late 2013)
Reverse Engineering: Addressing Critical Needs
Reverse Engineering: Addressing Critical Needs
Focused on Stator Components (Free)
We Come to You
Experienced Staff
State-of-the-Art Equipment
Supported by In-house CAD & Engineering
Digital Material Composition Analysis
Quick Turn Around
THANK YOU FOR YOUR TIME !
QUESTIONS ?
YOUR INFORMATION REQUESTS RECEIVE OUR HIGHEST PRIORITY
Jim Ford
630.240.6381
John Provencher
708.363.3838