© 2013 belden inc. | belden.com | @beldeninc belden confidential peter cox p.eng. project manager...
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© 2013 Belden Inc. | belden.com | @BeldenInc Belden Confidential
Peter Cox P.Eng.Project ManagerBelden Industrial Cable
Best Practices for VFD Cabling
© 2013 Belden Inc. | belden.com | @BeldenInc 2Belden Confidential
Peter Cox Bio
Licensed Professional Engineer
Worked in or as a consultant to Industry for 28yrs – mostly in a Drives and Industrials Controls
Participated in the testing of the first VFD cables developed with a major drive manufacturer in 1995
Did Beta testing of the 1336 Impact drive at Belden
© 2013 Belden Inc. | belden.com | @BeldenInc 3Belden Confidential
Learning Objectives
Understand Belden’s VFD Product Line
Belden Premium VFD
Belden CTC Construction Grade VFD
Understand the 4 Reasons to Specify VFD Cable
Common Mode Current
Capacitive Coupling/Cable Charging
Reflected Wave Voltage
Safety and Reliability
Discussion of Paralleling
© 2013 Belden Inc. | belden.com | @BeldenInc 4Belden Confidential
There is no standard for VFD cablesPerformance is all about Copper
• One thing you need to Remember…..
© 2013 Belden Inc. | belden.com | @BeldenInc 5
VFD Cable
• Connects Motor and Drive Power Circuit• Provides Reliable and Robust Connection• Protects against harmful noise
© 2013 Belden Inc. | belden.com | @BeldenInc 66
Belden VFD Cable Product OfferingClassic Foil/Braid Design
VFD Classic Cables• Four Conductor Foil / Braid Shield
Design VFD Cables(Three stranded TC Conductors + 1 Insulated Ground – green with a yellow stripe)
29500: 16 AWG VFD
29501: 14 AWG VFD
29502: 12 AWG VFD
29503: 10 AWG VFD
29504: 8 AWG VFD
29505: 6 AWG VFD
29506: 4 AWG VFD
29507: 2 AWG VFD
More Info in NP 235
Advantages – This construction offers thicker insulation for better performance and extended transmission distance
Other Designs – Interlocked Aluminum and Steel armored VFD products (part numbers available in NP316)
Much More Copper than 3C designs – Compared to Construction Grade these cables have as much as 3 times the copper at ground potential. Nearly as much as is in the circuit conductorsWhen comparing, look at product weights.
© 2013 Belden Inc. | belden.com | @BeldenInc 77
Belden VFD Cable Product OfferingSymmetrical Design
VFD Classic Cables• Symmetrical Design VFD Cables
(Three stranded TC Conductors +
3 Symmetrical BC Grounds +
2 Spiral Copper Tape Shields)
29528: 1 AWG VFD
29529: 1/0 AWG VFD
29530: 2/0 AWG VFD
29531: 3/0 AWG VFD
29532: 4/0 AWG VFD
29533: 250 AWG VFD (2KV)
29534: 350 AWG VFD (2KV)
29535: 500 AWG VFD (2KV)
More Info in NP 235
Advantages – The symmetrical ground design provides a balanced grounding system that is preferred in the industry on larger HP drives
Other Designs – Interlocked Aluminum and Steel armored VFD products (part numbers available in NP316)
We use 2 copper tapes with twice the surface area for better high frequency conduction. Contra helically applied where possible for lower inductance and higher performance. Much more effective and more expensive than a single tape used on all other products.
© 2013 Belden Inc. | belden.com | @BeldenInc 8© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 8
Application Issues
Challenges• Common Mode Current
• Capacitive Coupling and Cable Charging
• Reflected Wave Voltage – Motor and Cable
Life
• Application Reliability and Safety
Requirements• Reliability - high MTBF
• Manufacture recommendations
• Resistance to harsh environment
• NEC
• There it NO STANDARD FOR VFD cables
Customer Drivers• Energy Savings
• Low Total Cost of Ownership
• High Availability
• Safety: People & Processes
Belden• Quality and higher MTBF components in the
industry.
• The only product in the market that was co-
designed in conjunction with a major drives
manufacturer
• Global availability
• 17 years as a leading supplier of VFD cable
•
© 2013 Belden Inc. | belden.com | @BeldenInc 9© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 9
Application Issues Common Mode Current AKA Current Noise
Effects• Network Errors - Encoder Faults
• Loss of signal reliability analog and digital
signal error
• Ground plan noise pollution
• Motor bearing failures
• False stops and safety circuit trips and alarms
• EMI and RFI
Mitigation• Lowest Impedance ground path and Shielding
Make the cable the most attractive path for HF
currents
• High Surface area (4-8x) Conductors reduce HF
cable heating and reject less CMC
Definition• Current that flows between the drive and
motor by any path other than the 3
primary motor leads
• Kirchhoff’s Law – The sum of current at
any point is zero - All current must
return to the drive somehow
Why Belden• We put up to 3 times more copper at ground
potential than competitors “VFD” cables – with
flexible stranding we contain CMC 300% better
on our premium VFD
• Combination of foil braid, or 2 layers of CU
enhances performance
© 2013 Belden Inc. | belden.com | @BeldenInc 10Belden Confidential
What Does Common Mode Noise Look Like?
DRIVE FRAME
MOTOR WINDINGS
PE
MOTOR FRAME
LITTLE HF CURRENT
PVC
ARMOR OR SHIELD
PE GRID
PE TIE IN USER #1
PE TIE IN USER #2
PE TIE IN USER #n
SOLUTION: SHIELD CONTROLS HF NOISE CURRENT PATH
A+
A-
+
-PE
Iao
© 2013 Belden Inc. | belden.com | @BeldenInc 11
Motor Bearing Currents
11
High Voltage can also discharge through the bearings causing etching in the races and premature motor failure
© 2013 Belden Inc. | belden.com | @BeldenInc 12© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 12
Application Issues Capacitive - Coupling Cable Charging
Effects• Loss of motor torque or stalling
• False trips of drive overcurrent
• reduced system efficiency
• Charging of DE energized adjacent circuits
• Human safety issues
Mitigation• Lowest Capacitance 150ma/kft /conductor for
THHN vs. 50ma/kft/conductor for Belden VFD cable
• Shielding to prevent interaction between systems
Definition• Current that leaves the drive but is lost
due to capacitive interaction with other
cables. (Cable Charging)
Why Belden• Superior shielding
• Lowest capacitance
© 2013 Belden Inc. | belden.com | @BeldenInc 13© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 13
Application Issues Reflected Wave Voltage
Effects• Motor failure and downtime
• Cable failure (wet THHN)
Mitigation• Lowest Capacitance cable
• Output reactor (an immediate 3-8% efficiency loss)
Definition• A voltage spike originating at the motor,
caused by the impedance miss match
between the motor and cable
Why Belden• Our 600V cables have a minimum 5500V Corona
inception voltage (CIV) wet THHN can be 1600V or
less
• Lowest capacitance increases distance before
harmful voltages are created by up to 3x compared
to THHN
© 2013 Belden Inc. | belden.com | @BeldenInc 14
Reflected Wave Voltage
Application Issues
© 2013 Belden Inc. | belden.com | @BeldenInc 15© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 15
Application Issues Installation reliability and safety
Issues
• Cable/motor failure and degradation with PVC/Nylon
• Reference manufacturers cable selection instructions
• System noise issues
• Downtime
• Liability
© 2013 Belden Inc. | belden.com | @BeldenInc 16© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 16
The 2kv Myth
Issues
• In the 90’s VFDs lead to high failure rate on 600V THHN installations
• The engineering community began to specify 2000V THHN as a result
• 600V VFD cable, even the weaker construction grade, has higher dielectric strength
than 2Kv THHN
• Belden has never had a claim for dielectric failure in 16 years making 600V VFD Cable
• Code requirements are satisfied by 600V cable
© 2013 Belden Inc. | belden.com | @BeldenInc 17© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 17
Belden Features
Benefits• 50% more copper than most 3C symmetric
-300% better common mode current protection
• Enhanced flexibility
Feature• Foil Braid – Drain and full sized ground
© 2013 Belden Inc. | belden.com | @BeldenInc 18© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 18
Belden Features
Benefits• 4-8 times higher surface are means reduced
High Frequency Losses
• Cooler operation
• Enhanced flexibility
• Flexible motor supply rating
Feature• Flexible Stranding
© 2013 Belden Inc. | belden.com | @BeldenInc 19© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 19
Belden Features
Benefits• Reduced cable charging current
• Longer critical distances for reflected wave
buildup
• Longer cable life
Feature• Oversized wall thickness for lower
capacitance (0.045 vs 0.030)
© 2013 Belden Inc. | belden.com | @BeldenInc 20© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 20
Belden Features
Benefits• Better HF shielding than a single 5mil
• Reduced noise
• Enhanced flexibility
Feature• Dual copper tapes
© 2013 Belden Inc. | belden.com | @BeldenInc 21© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 21
Belden Features
Benefits• Corrosion resistance
• Thermal stability
• Connection reliability
Feature• Tinned stranding
© 2013 Belden Inc. | belden.com | @BeldenInc 22© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 22
Belden Features
Benefits• Reduced installation costs
Enhanced mechanical performance
Feature• ER rating
© 2013 Belden Inc. | belden.com | @BeldenInc 23Belden Confidential
• Input Line Reactor
• Output Line Reactor
• Common Mode Choke
• Motor terminator/snubber
• VFD Cable
A Comparison of Mitigation Strategies
© 2013 Belden Inc. | belden.com | @BeldenInc 24© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 24
Input Line Reactor
Benefits• Protect the drive from line transient damage
• Reduces Overvoltage faults
• Reduces Harmonic currents
Feature• Adds impedance on the Line side of the
drive
© 2013 Belden Inc. | belden.com | @BeldenInc 25© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 25
Output Line Reactor
Effects• Can be protective of non inverter motors
• Reduces Dv/Dt rise time downstream of the
reactor thus increases critical distance
• Can have harmonic interaction with Motor
• Has high associated efficiency losses (3-8%)
• Reduces motor voltage and torque
Feature• Adds impedance on the load side of the
drive
© 2013 Belden Inc. | belden.com | @BeldenInc 26© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 26
Common Mode Choke
Effects• Reduction of common mode current
• Reduces noise emissions
• Does no reduce EMI or RFI at all
Feature• Reduces common mode current
© 2013 Belden Inc. | belden.com | @BeldenInc 27© 2012 Belden Inc. | www.Belden.com | @BeldenInc | Page 27
Motor Terminator/Snubber
Effects• Reduction of reflected wave voltage
• Protection of motor and cable systems
• Great for vulnerable motors on very long leads
Feature• Burns of reflected wave energy as heat
at the motor
© 2013 Belden Inc. | belden.com | @BeldenInc 28Belden Confidential
Best:- Fine strand,
tinned copper
- XLPE Insulation
- 3 power conductors and 1 full size ground
- Foil and braid shields
- Manufacturers are in the on machine world
Pete Comber Competitive landscape
There is no standard for VFD cables, but we can categorize the product available:
Better:- Stranded copper
(some have tinned)
- XLP or THHN insulation
- 3 power conductors and 3 reduced size grounds
- Copper tape shield
- Manufacturers are in the power cable market
Good:- Bare copper
(think tray cable stranding)
- THHN insulation
- 3 power conductors and 3 reduced size grounds
- Copper tape shied
- Manufacturers are from any background
© 2013 Belden Inc. | belden.com | @BeldenInc 29Belden Confidential
• Upgraded THHN
• Construction Grade VFD XHHW
• 4C vs 3C Symmetric designs optimized for high frequency
Placeholder for Pete Comber Competitive landscape
There is no standard for VFD cables
© 2013 Belden Inc. | belden.com | @BeldenInc 30Belden Confidential
• No Common Mode Current Containment or Shielding Do you want to put the noisiest signals in the plant in unshielded cable?
• Cost does not include conduit and labor, with ER or Tray, these costs are dramatically reduced
• Faster “Ring Up” of Reflected Wave Voltages
• Higher cable charging current – Significant for small drives
• Short cable life on long runs - 10yr MTBF estimates-Not rated for 1600V
• No protection from capacitive coupling - Shielding
• Conduit transitions have high HF impedance-Reduced surface area
• Faults in THHN may not be catastrophic but periodic due to pin holes
Compared to THHN in Conduit
© 2013 Belden Inc. | belden.com | @BeldenInc 31Belden Confidential
• When we are comparing to Service Wire/General etc. And there is no spec or performance standard
• IF No Flexible Motor supply rating is required and flexibility is not desired
• The environment is not noise sensitive
• Cable Charging, and EMI, and RFI are the only issues
When to use Belden C Series (Construction Grade)
There is no standard for VFD cables
© 2013 Belden Inc. | belden.com | @BeldenInc 32Belden Confidential
• Directly connect the Shield at the Motor and Drive Only
• Do not introduce jumping off points for CMC through shield termination- Use Insulated glands
• Do not cut the shield between the motor and drive
• Do not use intermediate termination for the conductors if safely avoidable
• Maintain maximum spacing from sensitive circuits and route cables away from instrumentation and networks
• Reference the Belden VFD Termination guide
Advice for Proper Instalation
The following are best practices for VFD Cable installation and Termination:
© 2013 Belden Inc. | belden.com | @BeldenInc 33Belden Confidential
• Run a separate ground to the safety disconnect
• Avoid contact between the VFD cable grounds and shield with the ground in the disconnect
• If you must cut the grounds, terminate through an isolating terminal block or connection
Advice for Proper Instalation
Using VFD Cables with Safety Disconnects
© 2013 Belden Inc. | belden.com | @BeldenInc 34Belden Confidential
• Run the Videos
Termination videos
© 2013 Belden Inc. | belden.com | @BeldenInc 35Belden Confidential
• You may have issues you don’t know − Process measurement error
− Overcurrent or ground fault trips
− Loss of efficiency
− Network errors
− Remember that ground plane pollution is additive, one bad install may not cause a problem, but the accumulation of many bad installs may cause problems in the future
Scenario Based Q&A
A customer resiest VFD Cable because he always uses THHN without issue
© 2013 Belden Inc. | belden.com | @BeldenInc 36Belden Confidential
• What Questions should you ask− How long are the motor leads
− Is the motor wet
− What type of failures
− How large is the motor
• What are the likely causes of failure− Reflected wave voltage
− Bearing Currents
Scenario Based Q&A
A customer has contacted you because he experiences frequent motor failures on pumps driven by VFD’s
© 2013 Belden Inc. | belden.com | @BeldenInc 37Belden Confidential
• How is the drive cable run− How long are the motor leads
− What type of cable has been used?
• Does it correlate with drive starts stops enables
Scenario Based Q&A
A customer experiences network drops on the mixer ever since the line was upgradedCould it be drive related?
© 2013 Belden Inc. | belden.com | @BeldenInc 38Belden Confidential
• What issue do you think is the likely cause− How long are the motor leads
− What type of cable has been used?
Scenario Based Q&AA contractor has installed a large drive system for airport baggage handling. On commissioning many of the drives trip on overcurrent or will not run
© 2013 Belden Inc. | belden.com | @BeldenInc 3939
Paralleling and TC-ER Rating
• Installations savings
• Material– No metal conduit– No metal clad cable
• Labor– Less time
• Maintenance– Simplifies equipment moves, no
conduit to re-route / install
© 2013 Belden Inc. | belden.com | @BeldenInc 40Belden Confidential
Sizing Parallel VFD Cable:
Parallel Conductors
Amps 1/0 2/0 3/0 4/0 250 350 500
Single 170 195 230 260 290 350 430
Parallel 340 390 460 520 580 700 860
Triplex 510 585 690 780 870 1050 1290
Quad 680 780 920 1040 1160 1400 1720
Per NEC 310.15(16)When installed in Cable tray with air spacing, or in separate conduitsWhen parallel in Single conduit additional derate is required
© 2013 Belden Inc. | belden.com | @BeldenInc 41
Belden VFD Resources & Tools
• Industrial Cable VFD Page on Belden Website
• Unarmored VFD cable Termination Guide
• VFD Cable solutions guide
• Belden VFD Product Bulletin
• Belden VFD Cable Selection guide (based on Motor HP)
• Choosing the Right Cable for your Variable Frequency Drive (VFD) System White Paper
• Building a Reliable VFD System White Paper
• Control Engineering
• 1-800-Belden141