Rockwell Automation System Design User Manual

0 (0)
Rockwell Automation System Design User Manual

System Design for Control of Electrical Noise

Reference Manual

Important User Information

Because of the variety of uses for the products described in this

 

publication, those responsible for the application and use of this

 

control equipment must satisfy themselves that all necessary steps

 

have been taken to assure that each application and use meets all

 

performance and safety requirements, including any applicable laws,

 

regulations, codes and standards.

 

The illustrations, charts, sample programs and layout examples

 

shown in this guide are intended solely for purposes of example.

 

Since there are many variables and requirements associated with any

 

particular installation, Allen-Bradley does not assume responsibility

 

or liability (to include intellectual property liability) for actual use

 

based upon the examples shown in this publication.

 

Allen-Bradley publication SGI-1.1, Safety Guidelines for the

 

Application, Installation and Maintenance of Solid-State Control

 

(available from your local Allen-Bradley office), describes some

 

important differences between solid-state equipment and

 

electromechanical devices that should be taken into consideration

 

when applying products such as those described in this publication.

 

Reproduction of the contents of this copyrighted publication, in

 

whole or part, without written permission of Rockwell Automation,

 

is prohibited.

 

 

Throughout this manual we use notes to make you aware of safety

 

considerations:

 

 

 

 

 

 

 

 

Identifies information about practices or

 

ATTENTION

 

 

 

circumstances that can lead to personal injury or

 

!

 

 

 

death, property damage or economic loss.

 

 

 

 

 

 

 

Attention statements help you to:

identify a hazard

avoid a hazard

recognize the consequences

 

Identifies information that is critical for successful

IMPORTANT

application and understanding of the product.

 

 

 

 

Allen-Bradley is a registered trademark of Rockwell Automation.

 

Table of Contents

Preface

Who Should Use this Manual . . . . . . . . . . . . . . . . . . . . . . .

P-1

 

Purpose of this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . .

P-1

 

Contents of this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . .

P-2

 

Related Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . .

P-3

 

Conventions Used in this Manual . . . . . . . . . . . . . . . . . . . .

P-3

 

Chapter 1

 

Electrical Noise Control Overview

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1

 

What is Electrical Noise?. . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1

 

Understanding the Need for Electrical Noise Control . . . . . .

1-1

 

CE Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1

 

Best Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-2

 

Noise Control Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-2

 

Noise Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-2

 

Noise Victims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-4

 

Coupling Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-4

 

Conducted Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-4

 

Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-5

 

Mutual Inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-5

 

Electromagnetic Radiation . . . . . . . . . . . . . . . . . . . . . . .

1-6

 

Solutions for Reducing Noise . . . . . . . . . . . . . . . . . . . . . . .

1-6

 

Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-7

 

Measuring Effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-7

 

Chapter 2

 

High Frequency (HF) Bonding

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-1

 

Understanding the Source of Electrical Noise . . . . . . . . . . .

2-1

 

Noise Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-2

 

Noise Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-3

 

The Ground Plane Principle . . . . . . . . . . . . . . . . . . . . .

2-3

 

Extending the Ground Plane Principle . . . . . . . . . . . . . .

2-5

 

Grounding a PCB to the Drive Chassis . . . . . . . . . . . . .

2-5

 

Noise Solutions Using the Ground Plane Principle . . . . . . .

2-6

 

Grounding to the Component Mounting Panel. . . . . . . .

2-6

 

Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-7

 

Adjacent Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-8

 

Grid and Raised Floor. . . . . . . . . . . . . . . . . . . . . . . . . .

2-9

 

Mezzanine Floor. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-10

 

Machine Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-11

 

New Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-12

 

Existing Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-13

 

Limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-13

 

Grounding (Safety Earth) . . . . . . . . . . . . . . . . . . . . . . . . .

2-14

Publication GMC-RM001A-EN-P — July 2001

ii Table of Contents

Chapter 3

 

Segregating Sources and Victims Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-1

Understanding the Segregation Concept . . . . . . . . . . . . . . .

3-1

Noise Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-1

Ensuring CE Compliance at Build Time . . . . . . . . . . . . .

3-2

Zone Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-2

Component Categories . . . . . . . . . . . . . . . . . . . . . . . . .

3-3

Routing Wires and Cables Within a Panel . . . . . . . . . . . . . .

3-4

Wire and Cable Categories . . . . . . . . . . . . . . . . . . . . . .

3-6

Routing System Wires and Cables Between Panels. . . . . . . .

3-8

 

Chapter 4

 

Shielding Wires, Cables, and

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-1

Components

Understanding the Shielding Concept . . . . . . . . . . . . . . . . .

4-1

 

Ferrite Sleeves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-2

 

Ferrite Sleeve Limitations. . . . . . . . . . . . . . . . . . . . . . . .

4-4

 

Mixing Categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-4

Chapter 5

Filtering Noise

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . 5-1

 

Understanding the Filtering Concept . . . . . . . . . . . . . . .

. . . 5-1

 

Commercial AC Line Filters for Low Voltage Circuits

. . . 5-1

 

General Purpose 0-24V ac/dc Filters . . . . . . . . . . . .

. . . 5-2

 

Filter Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . 5-3

 

Performance Test Set-up . . . . . . . . . . . . . . . . . . . . .

. . . 5-4

 

Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . 5-4

 

Ultrasonic Transducers . . . . . . . . . . . . . . . . . . . . . . . . .

. . . 5-5

 

Xenon Flashing Beacons (strobe lights). . . . . . . . . . . . . .

. . 5-5

 

AC Line Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 5-5

 

Earth Leakage/Ground Fault . . . . . . . . . . . . . . . . . . .

. . 5-6

 

Chapter 6

 

Contact Suppression

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 6-1

 

Understanding Contact Suppression for AC Circuits . . . . .

. . 6-1

 

Methods of AC Contact Suppression . . . . . . . . . . . . .

. . 6-2

 

Understanding Contact Suppression for 24V dc Circuits . .

. . 6-3

 

Methods of DC Contact Suppression . . . . . . . . . . . . .

. . 6-3

 

Contact Suppression Effects . . . . . . . . . . . . . . . . . . . . . .

. . 6-4

 

Chapter 7

 

Power Distribution

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 7-1

 

Understanding Noise in Power Wiring . . . . . . . . . . . . . .

. . 7-1

 

Three-Phase Power Supplies. . . . . . . . . . . . . . . . . . . . . .

. . 7-1

 

Line Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 7-1

 

Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 7-3

 

Single Phase Power Supplies . . . . . . . . . . . . . . . . . . . . .

. . 7-4

Publication GMC-RM001A-EN-P — July 2001

 

Table of Contents

iii

 

 

 

 

24V dc Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4

 

24V dc Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-5

 

24V dc PSU Zoning Methods. . . . . . . . . . . . . . . . . . . . .

7-5

 

Linear PSU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-9

 

Special Applications for 24V dc PSUs . . . . . . . . . . . . .

7-11

 

Chapter 8

 

Motor Wiring

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1

 

Understanding Noise in Motor Power Wiring . . . . . . . . . . .

8-1

 

Shielding Motor Power Cables . . . . . . . . . . . . . . . . . . . . . .

8-2

 

Grounding Motor Power Cable Shields . . . . . . . . . . . . . . . .

8-2

 

Applying Ferrite Sleeves. . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3

 

Splicing Motor Power Cables . . . . . . . . . . . . . . . . . . . . . . .

8-3

 

Handling Excess Cable. . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4

 

Installing Long Motor Cables . . . . . . . . . . . . . . . . . . . . . . .

8-4

 

Chapter 9

 

High Speed Registration Inputs

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-1

 

Understanding Registration Inputs . . . . . . . . . . . . . . . . . . .

9-1

 

Noise Reduction Methods. . . . . . . . . . . . . . . . . . . . . . . . . .

9-2

 

Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-2

 

Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-2

 

Shared Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . .

9-2

 

Dedicated Power Supply. . . . . . . . . . . . . . . . . . . . . . . .

9-4

 

Detection Device Mounting. . . . . . . . . . . . . . . . . . . . . .

9-4

 

Proximity Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-5

 

Signal Noise Filter Options . . . . . . . . . . . . . . . . . . . . . . . . .

9-5

 

Single Voltage Input (24V or 5V). . . . . . . . . . . . . . . . . .

9-6

 

Dual Voltage Inputs (24V or 5V) . . . . . . . . . . . . . . . . . .

9-7

 

Registration Error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-8

 

Error Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-9

 

Software Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-9

 

Chapter 10

 

Encoders

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-1

 

Understanding Encoders . . . . . . . . . . . . . . . . . . . . . . . . .

10-1

 

Noise Reduction Methods. . . . . . . . . . . . . . . . . . . . . . . . .

10-1

 

Driver Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-1

 

Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-2

 

Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-2

 

Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-2

 

Power Supply Wiring Options . . . . . . . . . . . . . . . . . . . . .

10-3

 

Chapter 11

 

Measuring Noise Reduction

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11-1

Effectiveness

Understanding Noise Measurement. . . . . . . . . . . . . . . . . .

11-1

Publication GMC-RM001A-EN-P — July 2001

iv Table of Contents

 

Methods for Measuring Noise . . . . . . . . . . . . . . . . . . . . . .

11-1

 

Measuring Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11-2

 

Oscilloscope Specifications . . . . . . . . . . . . . . . . . . . . .

11-2

 

Oscilloscope Settings for Measuring Noise Peaks . . . . .

11-2

 

E-Field Sniffing Method . . . . . . . . . . . . . . . . . . . . . . . .

11-3

 

H-Field Sniffing Method . . . . . . . . . . . . . . . . . . . . . . .

11-4

 

Direct Voltage Measurement Method . . . . . . . . . . . . . .

11-4

 

Grounding Your Probe (reference ground) . . . . . . . . .

11-6

 

Ground Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11-7

 

Differential Measurements . . . . . . . . . . . . . . . . . . . . . .

11-7

 

Scope Probe Lead Extension . . . . . . . . . . . . . . . . . . . .

11-9

 

Checking Your Method for Effectiveness . . . . . . . . . . .

11-9

 

Identifying the Noise Source . . . . . . . . . . . . . . . . . . .

11-10

 

Intermittent Noise . . . . . . . . . . . . . . . . . . . . . . . . . . .

11-10

 

General Guidelines for Measuring Noise . . . . . . . . . . . . .

11-10

 

What are Acceptable Noise Levels? . . . . . . . . . . . . . .

11-10

 

Field Strength Meters . . . . . . . . . . . . . . . . . . . . . . . .

11-11

 

Monitoring for Noise. . . . . . . . . . . . . . . . . . . . . . . . .

11-11

 

Appendix A

 

Noise Control Supplement

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. A-1

 

Grounding Cable Shields . . . . . . . . . . . . . . . . . . . . . . . . .

. A-1

 

Pigtails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. A-1

 

Clamping at the Circular Section . . . . . . . . . . . . . . . . .

. A-2

 

Wire Segregation Test Results . . . . . . . . . . . . . . . . . . . . . .

. A-5

 

Test Set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. A-5

 

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. A-6

 

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. A-7

 

Switch-Mode DC Power Supplies . . . . . . . . . . . . . . . . . . .

. A-8

 

Background Information . . . . . . . . . . . . . . . . . . . . . . .

. A-8

 

Grounding the Common . . . . . . . . . . . . . . . . . . . . . . .

. A-9

 

DC Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-11

 

Positioning the PSU within the Panel . . . . . . . . . . . . . .

A-11

 

AC Line Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-12

 

Using Separate DC Power Supplies . . . . . . . . . . . . . . .

A-12

 

Using a Dynamic Braking Contactor . . . . . . . . . . . . . . . . .

A-13

 

Reducing Dynamic Braking Circuit Noise . . . . . . . . . . .

A-14

 

Bonding Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-15

 

Wire Forms an Antenna . . . . . . . . . . . . . . . . . . . . . . .

A-15

 

Inductance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-15

 

Noise Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-16

 

Appendix B

 

EMC Product Suppliers

EMC Product Suppliers. . . . . . . . . . . . . . . . . . . . . . . . . . .

. B-1

Publication GMC-RM001A-EN-P — July 2001

Preface

Who Should Use this Manual

Purpose of this Manual

Read this preface to familiarize yourself with the rest of the manual. The preface covers the following topics:

Who should use this manual

The purpose of this manual

Contents of this manual

Related documentation

Conventions used in this manual

Allen-Bradley support

Use this manual if you are responsible for the circuit design and layout of wiring panels or the installation and mounting of Allen-Bradley products. Specifically, the following disciplines should be included:

Circuit designers

Panel layout designers

Panel builders and electricians

Electrical technicians

In addition, you should have an understanding of:

Drive control and basic electronics

Appropriate electrical codes

This manual outlines the practices which minimize the possibility of noise-related failures and that comply with noise regulations. It gives you an overview of how electrical noise is generated (sources), how the noise interferes with routine operation of drive equipment (victims), and examples of how to effectively control noise.

This manual applies in general to Allen-Bradley drives products. For information on specific Allen-Bradley motion products refer to Noise Control Supplement - Motion Products Reference Manual (publication GMC-RM002x-EN-P).

Publication GMC-RM001A-EN-P — July 2001

P-2

Preface

 

 

Contents of this Manual

The contents of this manual are described in the table below.

Chapter

Title

Contents

 

 

 

 

Preface

Describes the purpose, background, and

 

 

scope of this manual. Also specifies the

 

 

audience for whom this manual is

 

 

intended.

 

 

 

1

Electrical Noise Control

Provides a brief understanding of the need

 

Overview

for electrical noise control, how noise

 

 

affects system performance, noise

 

 

coupling methods, and solutions.

 

 

 

2

High Frequency (HF) Bonding

Describes the ground plane principle and

 

 

provides techniques for bonding devices,

 

 

panels, machines, floors, doors, and

 

 

buildings.

 

 

 

3

Segregating Sources and

Describes how establishing zones within

 

Victims

your system for noise sensitive or noise

 

 

generating components can reduce

 

 

electrical noise coupling.

 

 

 

4

Shielding Wires, Cables, and

Describes how using shielded cable or

 

Components

steel shields can reduce electrical noise.

 

 

 

5

Filtering Noise

Describes how low-pass filters and ferrite

 

 

sleeves can reduce electrical noise.

 

 

 

6

Contact Suppression

Describes how contact suppressors for

 

 

relays and various other switches can

 

 

reduce electrical noise.

 

 

 

7

Power Distribution

Describes bonding, segregating, shielding,

 

 

and filtering techniques for use when

 

 

routing AC and DC power.

 

 

 

8

Motor Wiring

Describes shielding, grounding, and

 

 

splicing techniques for use with motor

 

 

wiring.

 

 

 

9

High Speed Registration

Describes how wiring sensitive to

 

Inputs

electrical noise benefits from proper noise

 

 

reduction strategies.

 

 

 

10

Encoders

Describes bonding, segregating, shielding,

 

 

and filtering techniques for use with

 

 

encoders.

 

 

 

11

Measuring Noise Reduction

Describes the equipment, methods, and

 

Effectiveness

various guidelines for measuring noise

 

 

levels and noise reduction effectiveness.

 

 

 

Appendix A

Noise Control Supplement

Provides background information on

 

 

specific topics related to electrical noise

 

 

control.

 

 

 

Appendix B

EMC Product Suppliers

Provides a list of EMC product suppliers,

 

 

the products they offer, and internet

 

 

website.

 

 

 

Publication GMC-RM001A-EN-P — July 2001

Preface

P-3

 

 

Related Documentation

The following documents contain additional information related to electrical noise control. To obtain a copy, contact your local Allen-Bradley office or distributor.

For:

Read This Document:

Document Number:

 

 

 

Specific advice on motion products

Noise Control Supplement - Motion Products

GMC-RM002x-EN-P1

Advice specific to large systems

Industrial Automation Wiring and Grounding Guidelines for Noise

1770-4.1

 

Immunity

 

 

 

 

Advice specific to large systems

Installing, Operating and Maintaining Engineered Drive Systems

D2-3115-2

 

(Reliance Electric)

 

 

 

 

Safety advice

Safety Guidelines for the Application, Installation, and

SGI-1.1

 

Maintenance of Solid-State Control

 

 

 

 

IEEE industry standards for electrical

IEEE Guide for the Installation of Electrical Equipment to

IEEE 518

equipment installation

Minimize Electrical Noise Inputs to Controllers from External

 

 

Sources

 

 

 

 

A text book on noise reduction techniques

Noise Reduction Techniques in Electronic Systems

N/A

 

Henry W. Ott

 

 

Published by Wiley-Interscience

 

 

 

 

A text book on grounding techniques for the

Grounding for the Control of EMI

N/A

control of EMI

Hugh W. Denny

 

 

Published by Don White Consultants

 

 

 

 

A text book on solving interference problems

Solving Interference Problems in Electronics

N/A

 

Ralph Morrison

 

 

Published by Wiley-Interscience

 

 

 

 

A technical paper on EMI emissions

EMI Emissions of Modern PWM ac Drives

N/A

 

Gary L. Skibinski, Russel J. Kerkman, & Dave Schlegel

 

 

IEEE Industry Applications Magazine, Nov./Dec. 1999

 

 

 

 

A text book on EMC

EMC for Product Designers

N/A

 

Tim Williams

 

 

Published by Newnes

 

 

 

 

1Available in future. Check with The Automation Bookstore.com or your Allen-Bradley sales representative for documentation availability.

Conventions Used in this Manual

The following conventions are used throughout this manual:

Bulleted lists such as this one provide information, not procedural steps.

Numbered lists provide sequential steps or hierarchical information.

Words that you type or select appear in bold.

When we refer you to another location, the section or chapter name appears in italics.

Publication GMC-RM001A-EN-P — July 2001

P-4

Preface

 

 

Publication GMC-RM001A-EN-P — July 2001

Chapter 1

Electrical Noise Control Overview

Chapter Objectives

What is Electrical Noise?

Understanding the Need for Electrical Noise Control

This chapter provides a brief understanding of the need for electrical noise control, how noise affects system performance, noise coupling methods and solutions. This chapter covers the following topics:

What is electrical noise

Understanding the need for electrical noise control

Noise control basics

Coupling mechanisms

Solutions for reducing noise

Implementation

Measuring effectiveness

Electrical noise is voltage spikes, generated by the routine operation of selected system components (sources), that interfere (due to a coupling mechanism) with the routine operation of other selected system components (victims).

In Europe, a system must satisfy EMC regulations. It must also work reliably without suffering from noise-induced failures.

CE Compliance

Most equipment is CE marked. This means it is certified to be compliant with European Directives which comprise two main requirements:

Potential noise sources must be limited in noise output to a specified level.

Potential victims of noise must be hardened to withstand a higher noise level.

Publication GMC-RM001A-EN-P — July 2001

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Electrical Noise Control Overview

 

 

In both cases, equipment must be installed to manufacturers recommendations to achieve compliance. The frequency range covered is 150kHz to 1GHz, though the upper limit is likely to be raised as operation frequencies increase.

Despite this, a CE compliant industrial drive system may still suffer functional failures due to electrical noise. Additional measures are often necessary to prevent noise from being coupled between source and victim. The frequency range involved in system failures is generally confined between 200kHz and 10MHz.

Best Practices

Noise Control Basics

Most industrial control products do not utilize high frequencies directly, but they can generate them in the form of noise. Logic circuits are affected by this noise, so you need to be able to control it.

Because it is far less expensive to apply noise control measures during system installation than it is to redesign and fix a malfunctioning system, we recommend you implement the best-practice procedures described in this document.

If basic measures are implemented rigorously, a reliable system should result. However, if just one wire is routed incorrectly or a filter is missed, it may be enough to cause problems. Experience shows that it is very difficult to ensure that these measures are applied 100% of the time. If all possible measures are taken (incorporating redundancy), the system is likely to be more tolerant of minor mistakes in implementation.

A typical industrial control system will contain a mixture of noise sources and potential victims. Problems are caused when a coupling mechanism is introduced.

Noise Sources

Typical noise sources include:

Mechanically switched inductive loads create intense intermittent noise.

PWM drive power outputs create intense continuous noise.

Switch-mode DC power supplies can create continuous noise.

Publication GMC-RM001A-EN-P — July 2001

Electrical Noise Control Overview

1-3

 

 

Microprocessor clocks can generate high levels of noise at the clock frequency and its harmonics.

Contact switching.

Of the noise sources listed above, only contact switching noise can be reduced at the source by the system builder.

Refer to the figure below for an example of a typical noise source.

Figure 1.1

Switch-Mode Power Supply Noise Measurement

AC

+24V

No load connected

 

 

Line

24V dc PSU

 

Filter

DC common

Noise voltage

 

measured here

 

 

Ground Plane - conductive metal panel

Refer to Figure 1.2 for an example of six volt noise spikes from a typical 24V dc power supply. The spikes usually contain frequencies above 10 MHz.

Figure 1.2

Switch-Mode Power Supply Noise

10V

8

6

4

2

0

-2

-4

6.0V pk -6

-8

-10V

-1

0

1

2

3

4

5

6

7

8

9 ms

Sitop Power 20 with 3 phase input - no load

Common Mode Noise +24 Volts to Backplane

Publication GMC-RM001A-EN-P — July 2001

1-4

Electrical Noise Control Overview

 

 

Noise Victims

Typical noise victims include the following:

Microprocessor controlled devices

Analog devices

Encoder and registration interfaces

Refer to Figure 1.3 for an example of a typical victim.

Figure 1.3

A victim TTL gate is easily triggered

Noisy circuit carrying 6V spikes comprising mainly 10 MHz

5V TTL gate

100 pF = 200 Ω 1

@ 10 MHz

50 Ω

Victim TTL gate receives 1.2V spikes

Signal Source (zero impedance)

Coupling Mechanisms

1Refer to the section Capacitance below for an explanation of the 200 ohm impedance. Generally, most potential victims are better protected than this.

The source noise level and the victim’s sensitivity are normally outside the control of the system designer so that it is necessary to concentrate on the transmission of noise between them.

The coupling mechanism is the means by which electrical noise interferes with the routine operation of equipment. This section describes the four common coupling mechanisms for electrical noise transmission.

Conducted Noise

Noise is conducted directly by system power wiring. A common route for conducted noise is the 24V dc distribution wiring.

Publication GMC-RM001A-EN-P — July 2001

Electrical Noise Control Overview

1-5

 

 

Capacitance

At radio frequencies (RF) the capacitance between two adjacent wires is significant. Two insulated wires touching each other and only 1.0 meter (39.0 in.) long form a capacitance of approximately 100 pF (Pico Farads). At 10 MHz the impedance is only 200 ohms.

Fortunately, the effect reduces as the square of the separation distance. Refer to Figure 1.4 for an example of capacitive coupling.

Figure 1.4

Capacitive Coupling

Stray

 

 

Circuit A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

capacitance

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Separation distance

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Circuit B

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mutual Inductance

At radio frequencies (RF) the inductance of a straight wire is significant. A length of wire 1.0 meter (39 in.) has an inductance of approximately 1.0 H (Micro Henry). At 10 MHz the impedance is 60 ohms.

Two adjacent wires have mutual inductance forming a transformer. Fortunately, the effect reduces as the square of the separation distance. Refer to Figure 1.5 for an example of inductive coupling.

Figure 1.5

Inductive Coupling

Circuit A

Stray inductance

Magnetic coupling

Separation distance

Circuit B

Publication GMC-RM001A-EN-P — July 2001

1-6

Electrical Noise Control Overview

 

 

Electromagnetic Radiation

Solutions for Reducing Noise

An example of electromagnetic radiation is radio transmission. Industrial control wiring systems are large, wideband antenna which radiate noise signals to the world. These signals (together with conducted noise) are the primary target of the European regulations, but rarely cause system malfunctions.

Noise reduction solutions are categorized as coupling reduction and source reduction. There are four main methods used to reduce the coupling of noise between source and victim. However, contact suppression is the only source reduction technique that can be directly applied by the system builder. Refer to the table below for a summary.

This method:

In this

Is defined as:

For more

 

category:

 

information refer to:

 

 

 

 

HF (high frequency)

Coupling

Maintaining all metalwork at the same electrical potential. This

The chapter High

Bonding

Reduction

method is low cost and the basis for all other methods. It works by

Frequency (HF)

 

 

ensuring all equipment chassis are at the same potential at all

Bonding.

 

 

frequencies. If different potentials exist the voltage difference is

 

 

 

seen as common-mode noise on all interconnecting wiring.

 

 

 

 

 

Segregation

Coupling

Separating sources and victims of electrical noise into zones. Noise

The chapter

 

Reduction

coupling reduces with the square of separation distance. Zoning is

Segregating Sources

 

 

zero cost (within limits).

and Victims.

 

 

 

 

Shielding

Coupling

Using shielded cable and steel barriers (Faraday cage effect) to

The chapter Shielding

 

Reduction

reduce electrical noise. Because of its relatively high cost, shielding

Wires, Cables, and

 

 

is used with discretion.

Components.

 

 

 

 

Filtering

Coupling

Using low-pass filters to attenuate RF noise. Relatively low cost but

The chapter Filtering

 

Reduction

impractical for every wire.

Noise.

 

 

 

 

Contact

Source

Adding contact suppression to mechanical switches to reduce noise.

The chapter Contact

Suppression

Reduction

Generally, the one noise source directly influenced by the system

Suppression.

 

 

builder.

 

 

 

 

 

Publication GMC-RM001A-EN-P — July 2001

Electrical Noise Control Overview

1-7

 

 

Implementation

Implementation involves applying the methods summarized in the table on page 1-6 to the applications as shown in the table below.

 

This application:

Is defined as:

For more

 

 

 

 

information refer to:

 

 

 

 

 

Routing AC and DC

Applying bonding, segregating, shielding, and filtering techniques to

The chapter Power

 

power

AC and DC power supplies and the associated wiring.

Distribution.

 

 

 

 

 

Routing motor

Applying shielding, grounding, and splicing techniques to motor

The chapter Motor

 

power cables

power cable installation.

Wiring.

 

 

 

 

 

Wiring high speed

Applying all the noise reduction methods available to improve the

The chapter High

 

registration inputs

performance of noise sensitive wiring.

Speed Registration

 

 

 

 

Inputs.

 

 

 

 

 

Routing encoder

Applying bonding, segregating, shielding, and filtering techniques to

The chapter Encoders.

 

power cables

encoder installation.

 

 

 

 

 

 

Measuring Effectiveness

Measuring noise reduction effectiveness involves using an

 

 

 

oscilloscope to test for noise during implementation. It also involves

 

 

 

monitoring for noise after implementation should updates to the

 

 

 

system affect system performance.

 

 

 

 

 

 

This application:

Is defined as:

For more

 

 

 

 

information refer to:

 

 

 

 

 

Measuring

Testing for electrical noise during implementation, identifying the

The chapter

 

effectiveness

sources of noise, determining acceptable noise levels, and

Measuring Noise

 

 

monitoring for noise on an on-going basis.

Reduction

 

 

 

 

Effectiveness.

 

 

 

 

 

Publication GMC-RM001A-EN-P — July 2001

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Electrical Noise Control Overview

 

 

Publication GMC-RM001A-EN-P — July 2001

Chapter 2

High Frequency (HF) Bonding

Chapter Objectives

Understanding the Source

of Electrical Noise

This chapter describes the ground plane principle and techniques to extend the ground plane to devices, panels, machines, floors, doors, and buildings. This chapter covers the following topics:

Understanding the source of electrical noise

Noise solutions using a ground plane

Grounding (safety earth)

The most common source of electrical noise is due to switching of PWM output stages.

Two examples of how noise is generated by a drive system are given on the following pages.

Publication GMC-RM001A-EN-P — July 2001

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High Frequency (HF) Bonding

 

 

Noise Example 1

The transistors impose a 600V step change in the wire B (typically less than 200nS). Stray capacitance A charges very rapidly causing a current spike. This is the dominant noise source in PWM (Pulse Width Modulated) drive systems.

The current circulates through stray capacitance C, bonding impedance D, bonding impedance E, bonding impedance F, and back to stray capacitance A. A voltage spike will appear between motor frame and machine structure (Vd), between machine structure and the panel (Ve) and between the panel and drive chassis (Vf).

The circuit of an encoder mounted on the motor will then have a voltage spike of amplitude Vd + Ve relative to the panel and to any input circuit on the panel, potentially a noise victim.

The noise voltages are proportional to the impedance of the bonds (voltage = current x impedance). If these are reduced to zero, no voltage will appear between encoder and panel.

Figure 2.1

Switching noise affecting encoder signal

Drive

 

+600V dc

Motor

 

 

 

 

Stray

 

 

 

capacitance

Windings

 

 

 

Heatsink

 

 

 

(connected

 

B

C

to chassis)

A

 

 

Transistor block

 

 

 

 

Encoder

 

 

DC common

 

F

 

Impedance due to

D

 

poor bonding

 

 

 

 

Panel

 

E

Machine Structure

 

 

 

The quality of bonding techniques applied during

IMPORTANT

installation directly affects the noise voltages

 

 

 

between system components.

 

 

Publication GMC-RM001A-EN-P — July 2001

High Frequency (HF) Bonding

2-3

 

 

Noise Example 2

Stray capacitance I charges very rapidly. Current circulates via stray capacitances H, bond G, bond F, and A. In this way, a voltage Vf + Vg is developed between the drive chassis and true-ground.

Any remote equipment grounded to this true-ground and wired to the drive will have this noise voltage imposed upon its incoming signal.

Figure 2.2

Switching noise affecting incoming power

 

 

 

 

 

 

 

 

 

Drive

+600V dc

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I

 

Stray

 

 

 

 

 

Stray capacitance

 

capacitance

 

 

 

 

 

to ground

Heatsink

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(connected

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

to chassis)

Transistor

 

 

 

 

 

 

 

 

 

A

 

 

 

 

 

 

 

 

 

 

block

AC line

 

 

H

 

DC common

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

F

Impedance due to

 

 

 

 

 

 

 

poor bonding

 

 

 

 

 

 

 

G

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Panel

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Many other noise sources exist in a typical system and the advantage of good bonding holds true for all.

The Ground Plane Principle

The purpose of High Frequency (HF) bonding is to present a defined low impedance path for HF noise currents returning to their source.

 

Noise current must and will return to source. If a safe

IMPORTANT

path is not provided, it may return via victim wiring

 

 

 

and cause circuits to malfunction.

 

 

Most textbooks on radio frequency (RF) techniques describe the ground plane (GP) as the ultimate ground reference and an absolute requirement for controlling RF current paths.

Publication GMC-RM001A-EN-P — July 2001

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High Frequency (HF) Bonding

 

 

The ground plane principle was originally developed by printed circuit board (PCB) designers for high frequency circuits. In multi-layer PCBs a minimum of two copper layers are used with one being designated the ground or common. This layer covers as large an area as possible and each IC common is tied directly to it. In addition, each IC Vss (+5V) pin is decoupled by a 0.1 F capacitor to the ground plane as close as possible to the pin. The capacitor presents a very low impedance at RF hence any induced noise current generates minimal voltage.

The fundamental property of a ground plane is that every point on its surface is at the same potential (and zero impedance) at all frequencies. At high frequencies this is more effective than the use of single point grounding schemes. This is because wire has significant inductance at RF and just a few inches can create an unacceptable voltage drop. Refer to the section Bonding Surfaces in Appendix A for more information.

Figure 2.3

Ground plane layer in a double-sided printed circuit board

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vss pin

 

 

Vdd pin

 

 

 

 

 

 

 

 

(+5V)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Decoupling Capacitor

 

 

(common)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Vss to ground)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ground plane

 

Integrated Circuit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

layer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Insulation

layer Interconnect layer

Ground plane construction has proved so successful that it is now universal in PCB design for all but the most price-sensitive and low frequency circuits. Single-sided PCBs are not generally used for RF or TTL circuits.

Publication GMC-RM001A-EN-P — July 2001

High Frequency (HF) Bonding

2-5

 

 

Extending the Ground Plane Principle

The same theory holds true regardless of scale, (the earth being the ultimate and literal ground plane) and can be used at control cabinet level or even building level, but requires rigorous implementation.

A ground plane does not have to be flat, but gentle curves prove more effective than sharp corners. Area is what matters. Even the outer surface of a machine structure can be used.

Grounding a PCB to the Drive Chassis

In the figure below, a PCB ground plane is extended by bonding it to the drive chassis.

Figure 2.4

PCB ground plane extended to the drive chassis

Drive chassis

PCB copper interconnection layer

PCB copper ground plane layer

bonded to drive chassis

Printed circuit board (PCB)

Guidelines for the system builder include:

When permitted, the control circuit common should be grounded.

Some products do not permit grounding of the control common, but may allow grounding to chassis via a 1.0 F, 50V ceramic capacitor. Check your installation manual for details.

Publication GMC-RM001A-EN-P — July 2001

2-6

High Frequency (HF) Bonding

 

 

Noise Solutions Using the

Ground Plane Principle

In this section, examples of how to apply the ground plane principle are described.

Grounding to the Component Mounting Panel

In the example below, the drive chassis ground plane is extended to the mounting panel. The panel is made of zinc plated steel to ensure a proper bond between chassis and panel.

Figure 2.5

Drive chassis ground plane extended to the panel

Drive ground plane (chassis) bonded to panel

Note: Where TE and PE terminals are provided, ground each separately to the nearest point on the panel using flat braid.

Plated vs. Painted Panels

In an industrial control cabinet, the equivalent to the copper ground layer of a PCB is the mounting panel. To make use of the panel as a ground plane it must be made of zinc plated mild steel or if painted, the paint must be removed at each mounting point of every piece of metal-clad equipment (including DIN rails).

Zinc plated steel is strongly recommended due to its inherent ability to bond with the drive chassis and resist corrosion. The disadvantage with painted panels, apart from the cost in labor time to remove the

Publication GMC-RM001A-EN-P — July 2001

High Frequency (HF) Bonding

2-7

 

 

paint, is the difficulty in making quality control checks to verify if paint has been properly removed, and any future corrosion of the unprotected mild steel will compromise noise performance.

Plain stainless steel panels are also acceptable but are inferior to zinc plated mild steel due to their higher ohms-per-square resistance.

Though not always available, a plated cabinet frame is also highly desirable since it makes HF bonding between panel and cabinet sections more reliable.

Painted Components

Mating surfaces must be cleaned of paint and the exposed surfaces protected against corrosion with conductive paint or petroleum jelly.

Anodized Aluminum Components

Mating surfaces must be cleaned of anodizing and the exposed surfaces protected against corrosion.

EMC Filters

Filter performance depends entirely on close coupling between the filter case and the drive chassis (or other load chassis). They should be mounted as close as possible to the load and on the same panel. If a painted panel is used, short braid straps should be used to tie the two chassis together. As a temporary remedy, an effective means of coupling filter case and drive chassis is to lay a single piece of aluminum foil beneath the two chassis.

Doors

For doors 2 m (78 in.) in height, bond with two or three (three is preferred) braided straps (top, bottom, and center).

EMC seals are not normally required for industrial systems.

Publication GMC-RM001A-EN-P — July 2001

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High Frequency (HF) Bonding

 

 

Adjacent Panels

Bond adjacent panels by mounting multiple flat straps between the panels. As an alternative, mount a filler plate between the panels using multiple fasteners along the edges of the plate.

Figure 2.6

Panel ground plane extended to adjacent panels

Adjacent panels bonded to extend the ground plane

Cabinet ground plane (component mounting panel)

Ground plane extended to side panel by bonding to main panel

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High Frequency (HF) Bonding

2-9

 

 

Grid and Raised Floor

Bonding cabinet panels and machine chassis to a ground grid below a raised floor is the best possible grounding scheme and commonly used in computer mainframe installations, but rarely used in industrial environments.

Ideally the grid squares should be 1 m (39 in.) or less.

Figure 2.7

Panel ground plane extended to a grid beneath a raised floor

Machine structure used as ground plane

Cabinet ground plane (panel) bonded to floor ground plane

Grid ground plane. Copper strip laid on the floor, covered by a false floor (also bonded to machine structure).

Publication GMC-RM001A-EN-P — July 2001

2-10

High Frequency (HF) Bonding

 

 

Mezzanine Floor

A mezzanine floor makes a very effective ground plane if the floor panels are aluminum or galvanized steel and bonded at their edges every 1 m (39 in.) minimum. Machine structure, floor, and both panels form one large ground plane.

Figure 2.8

Panel ground plane extended to a mezzanine floor

Mezzanine floor ground plane

Cabinet ground plane (panel) bonded

to Mezzanine floor ground plane

Machine structure bonded to floor

 

Machine structure

Machine structure used as ground plane

bonded to floor

 

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High Frequency (HF) Bonding

2-11

 

 

Machine Structure

If the machine structure covers a large portion of the system area and is constructed of a conductive material with all sections closely bonded, then it too will form an excellent ground plane. Care should be taken to ensure paint is removed at the bonds and the connections protected against corrosion.

Figure 2.9

Panel ground plane extended to the machine structure

Machine structure used as ground plane

Panel ground plane bonded to structure ground plane by clean and dirty wireways

Bond the panel(s) to the machine structure as tight as possible, but if this proves difficult, construct a low impedance path using the following guidelines:

Use a zinc-plated tray, as wide as practical, and join sections by overlapping with several fasteners across the width. The perforations will not reduce performance (refer to Figure 2.10).

EMC trunking (plated at joint surfaces with conductive gaskets) also makes a good bond.

Short and wide is the requirement for any HF bonding material. Panel(s) should be located as close to the machine structure as practical and the bond should be firmly attached at both the machine structure and the control panel (not the cabinet outer panels).

Multiple trays/trunking are better.

Note that copper wire safety earth bonding is still required. Refer to the section Grounding (Safety Earth) at the end of this chapter for more information.

Publication GMC-RM001A-EN-P — July 2001

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High Frequency (HF) Bonding

 

 

Figure 2.10

Extending the panel ground plane using cable tray

Multiple fasteners

Zinc plated steel main panel

Same width

Must be directly bonded here and at the machine structure

Zinc plated steel cable tray (wider is better)

Note: A ground plane does not have to be flat.

New Buildings

In new installations it is possible to specify that the structural steel columns are bonded together beneath the floor. This is similar in concept to the special floor grid shown earlier (refer to Figure 2.7), but inferior due to the large grid squares.

The panels are bonded by a flat strip or braid to the nearest steel column. The floor, machine structure, and panels form a large, but relatively ill-defined ground plane.

Figure 2.11

Panel ground plane extended to the building

Machine structure used as ground plane

Steel

Column

Steel

Column

Cabinet ground plane (panel) bonded to nearest building steel

Building ground plane. Copper strip laid into the floor bonding columns together.

Publication GMC-RM001A-EN-P — July 2001

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