© 2013 Belden Inc. | belden.com | @BeldenInc Belden Confidential Peter Cox P.Eng. Project Manager Belden Industrial Cable Best Practices for VFD Cabling

© 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


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


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


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.


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

•


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


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


Motor Bearing Currents

11

High Voltage can also discharge through the bearings causing etching in the races and premature motor failure


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


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


Reflected Wave Voltage

Application Issues


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


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


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


Belden Features

Benefits• 4-8 times higher surface are means reduced

High Frequency Losses

• Cooler operation


• Flexible motor supply rating

Feature• Flexible Stranding


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)


Belden Features

Benefits• Better HF shielding than a single 5mil

• Reduced noise


Feature• Dual copper tapes


Belden Features

Benefits• Corrosion resistance

• Thermal stability

• Connection reliability

Feature• Tinned stranding


Belden Features

Benefits• Reduced installation costs

Enhanced mechanical performance

Feature• ER rating


• Input Line Reactor

• Output Line Reactor

• Common Mode Choke

• Motor terminator/snubber

• VFD Cable

A Comparison of Mitigation Strategies


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


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


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


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


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


• 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


• 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


• 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


• 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:


• 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


• Run the Videos

Termination videos


• 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


• 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


• 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?


• 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


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


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


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

http://www.belden.com/products/browse/industrialwc/vfd-cable.cfm

http://www.belden.com/products/browse/industrialwc/vfd-cable.cfm

http://www.belden.com/resourcecenter/tools/installguides/upload/VFD_Cable_Termination_Guide.pdf

http://www.belden.com/resourcecenter/tools/installguides/upload/VFD_Cable_Termination_Guide.pdf

http://www.belden.com/resourcecenter/catalogs/upload/Variable-Frequency-Drive-VFD-Cable-Solutions-Brochure-VFD_Brochure.pdf

http://www.belden.com/docs/upload/NP316.pdf

http://www.belden.com/pdfs/Techpprs/VFD.pdf

http://www.belden.com/pdfs/Techpprs/VFD.pdf

http://www.belden.com/docs/upload/VFD_Choosing_WP.pdf



http://www.belden.com/docs/upload/WP-VFDCablingPractices.pdf

http://www.belden.com/docs/upload/WP-VFDCablingPractices.pdf

http://www.controleng.com/home/single-article/the-right-system-components-are-critical-to-maximizing-the-energy-saving-potential-of-vfds/09853e3bb20ce14dfae26752dd38e84c.html

Documents

© 2013 Belden Inc. | belden.com | @BeldenInc Belden Confidential Peter Cox P.Eng. Project Manager Belden Industrial Cable Best Practices for VFD Cabling