Why Conventional EMC Testing is Insufficient for Functional Safety (and What To Do About It)
Keith Armstrong

Electromagnetic Compatibility (EMC) is generally verified/validated simply by testing the performance of electronic products and equipment using standardised test methods, in an EMC laboratory. This could be called the ‘conventional’ approach to achieving EMC.

‘Functional safety’ means the reduction of risks due to operational (functional) errors or malfunctions, to acceptable levels, over the anticipated lifetime of a product.

There have long been concerns [1] that the traditional approach to EMC is inadequate for the achievement of functional safety. In all safety engineering disciplines other than EMC, it is accepted that it is insufficient to rely on testing alone to prove the robustness of a design.

Instead, the achievement of acceptable safety risks are verified/validated using an approach based that employs a wide variety of methods (including, but not limited to testing) to verify the adequacy of the safety design, and how much confidence can be had in it.

This paper describes why the conventional EMC testing approach is insufficient as the sole means of demonstrating that a design’s EM characteristics are adequate for functional safety reasons over the anticipated lifecycle.

It then goes on to describe what EM engineering, verification and validation techniques are required, where errors or malfunctions in electronics (hardware and software or firmware) could result in unacceptable functional safety risks.

The techniques described are based on the forthcoming second edition of IEC TS 61000-1-2, the IEC’s basic standard on EMC for Functional Safety, which has been rewritten to become what is essentially the ‘missing EMC Annex’ to IEC 61508, the IEC’s basic standard on functional safety for complex electronic systems.

Some industrial companies (for example, some manufacturers of flight-critical avionics) already employ verification/validation methods that go well beyond their industry’s standardised EMC test requirements, to help them achieve confidence that their designs will achieve adequate functional safety over their lifecycles.

But the use of good ‘EMC-for-functional-safety’ practices is very far from being as common as it needs to be, especially given the very rapid increase in the use of increasingly complex electronic devices and software/firmware in areas where errors or malfunctions could increase safety risks, in almost all areas of industry from household appliances, through transport and healthcare to national security.


Full-day workshop on EMC for Functional Safety
Keith Armstrong

This workshop is suitable for all safety engineers and their project managers, and all EMC (electromagnetic compatibility) engineers and their project managers, regardless of their level of expertise.

Departmental and general managers will also benefit. Financial managers, product liability lawyers, government officials and anyone concerned with risk analysis (safety and/or financial) will also find material of interest.

Complex electronic technologies (hardware and software) are increasingly being used in safety-related and safety-critical equipment systems, and these technologies are themselves rapidly developing in complexity.

All electronic technologies have a tendency to suffer from electromagnetic interference (EMI), and the more complex and sophisticated they become, the more susceptible they are.

Functional Safety engineering has developed over the years, especially in recent years to cope with software, resulting in the basic functional safety standard for electrical, electronic and programmable electronic systems: IEC 61508.

IEC 61508 requires that EMI be taken into account in the achievement of acceptably low functional safety risks – but it doesn't say how this should be done.

The usual assumption is that complying with the regular emissions and immunity test standards is sufficient, but this couldn't be more wrong.

EMC test standards have developed independently of safety engineering, over the decades, and the two disciplines have developed different concepts and terminologies, making mutual understanding very difficult.

Commercial/industrial test standards are often inappropriate for safety purposes, and even military and aerospace tests that do attempt to deal with safety issues are constrained by what can be repeatably achieved by practical test equipment at an affordable cost and timescale.

To demonstrate that a design had EMC characteristics that would reliably ensure acceptably low functional safety risks over its operational lifecycle, would require an EMC testing plan that no organisation, even governments, could possibly afford. And anyway, it is a general safety engineering principal that testing on its own is insufficient to prove a design with sufficient confidence.

The IEC has been developing a standard on how to deal with EMC for Functional Safety, IEC 61000-1-2, for ten years now, and it is just coming up to its second edition as an IEC Technical Specification. It is anticipated that in a few years, it will become a full standard. The committee for this standard is unusual, in that it consists of both EMC and Functional Safety experts, and quite a lot of its time has been spent in the EMC people getting to understand functional safety engineering jargon and principles, and vice-versa.

The draft 2nd Edition of IEC 61508 references IEC 61000-1-2 for all EMC issues.

This workshop describes the analysis, design and verification/validation methodology being adopted by IEC 61000-1-2, and is presented by members of its committee.

The workshop has four papers, each approximately 1 hour of presentation and 30 minutes for discussions. The presented material will include plenty of practical examples. The workshop consists of an overview of the safety lifecycle, plus what is happening in standardisation, and then an in-depth look at the first items in the IEC 61508 safety lifecycle:

1) A brief overview of the whole lifecycle (point of view of a manufacturer of safety-related systems)
2) Assessing the lifecycle environments (both EM and physical/climatic)
3) Risk assessment and creating the Safety Requirement Specification (SRS)
4) EM/safety planning

Workshops in future years will discuss the remaining safety lifecycle issues.

This is not a subject that uses much mathematics — it is more about employing existing techniques and procedures in new ways to achieve quantifiable levels of safety when considering the possibilities for EMI.

Circuit Protection Devices – Selection, Applications & Case Studies
Ashish Arora

Protection against over-voltage, over-current, and over-temperature is typically accomplished using a variety of devices such as fuses, circuit breakers, thermal cutoffs, positive temperature coefficients (PTCs), metal oxide varistors (MOVs), power zeners, bi-metallic strips etc. The suitability of a device for a particular application depends on many factors such as transient and steady state voltage, current and power ratings, source impedance, environmental conditions etc. An appropriately selected device should be capable of protecting the system under the worst case operating conditions. A designer has available several tools (for example PSpice, Ansys, etc) to determine the worst case operating parameters for a particular application. Standards such as IEEE Std. C62.41 further aid the designer in determining the suitability of the selected protection device. In addition, potential user misuse of the system should also be considered when selecting a protection device.

This paper discusses the design, typical use and failure modes of selected circuit protection devices. An understanding of the device characteristics and failure modes will allow a designer to select the appropriate device for the application. Selected case studies are presented to demonstrate the problems associated with the absence or inappropriate selection of these devices.

Available USB and AA Battery Power
Ken Budoff

The ubiquitous presence of USB and AA type batteries (Alkaline, Ni-MH, Lithium primary) as power sources for small electronic gadgets is largely accepted without inspection by safety professionals.  Measurements of the amount of available current and power into low resistance loads from a sample of both sources is presented.   Find out what the data sheets don’t say.  Implications to safety and certifications are considered.

Modeling of Reactions of Cathode with Nonaqueous Solvents in Li-ion Batteries
W. F. Chen

The reaction of Li1-xCoO2 with nonaqueous solvents has been successfully modeled by D. D. MacNeil, and J. R. Dahn (Journal of The Electrochemical Society, 149 (7) A912-A919 (2002)).  The reaction proceeds in a clear stepwise manner through solid phase as a function of temperature.  In the same article, a kinetic description for the stepwise reaction of Li_0.5CoO₂ in EC/PC was developed using successive Avrami-Erofeev reaction models.  Kissinger estimated the activation energy of this reaction using the DSC measurements and a special reaction function dy/dt=k(1-y)*2 where t is the time, k is the reaction constant and y is the ratio of the amount of cathode already reacted..

In this paper, the authors take a different approach by using the integral form of the reaction function G(y)=k t instead of the differential form dy/dt=k.f(y).  The SOC (state of charge) is introduced into the model by assuming G(y) is proportional to SOC and the constant of proportionality C is the amount determined by the Li_1-xCoO₂ available for the reaction.  Let TTF be the time when the 2^nd phase of the decomposition of Li_1-xCoO₂ starts.  That is, TTF is the time when swelling starts to accelerate.  Then the relationship between SOC, the absolute temperature (T) and TTF can be described by the following equation:

Applying log to both side of the above equation, we obtain:

Note that for any given SOC, Ln (TTF) is a linear function of 1/T and the slope is equal to E/R. 

Note also that this methodology is independent of the reaction function f(y) and that Kissinger’s model assumes f(y)=(1-y)*2. 

The empirical data (TTF vs T) obtained from the Li-ion polymer cells at three different SOC’s (corresponding to 3.85V, 4.0 V and 4.2V) shows that the slope, E/R, is the same for all three SOC’s.   Therefore, we can estimate the activation energy E by dividing the slope by the gas constant R.  The E estimated using this methodology is 1.21 eV which is reasonably close to the 1.18 eV estimated by the Kissinger method using DSC data.

The authors have also compared the TTF’s of two different cathode materials (LCO and NCM) at 100% SOC using the method described in this article.

Europe's REACH Regulation - Busting the 1 Tonne Myth
Lauren Crane

REACH is the European Regulation that addresses chemical classification, documentation and labeling, and related authority communications. It came into effect in June of 2007, and has several staged deadlines from now until 2018 and later. One of the most common misconceptions about REACH is that it only applies when you are importing more that 1000kg of a substance into Europe in a given year. Actually, REACH has criteria that apply now even for quantities as small as 1 gram. This presentation will provide a brief over view of REACH and some key high level concepts, but then delve quickly into the criteria that are applicable regardless of tonnage. The presentation will address packaged chemicals bundled with equipment, such as a cleaners, paints, lubricants and ink cartridges, and 3rd party chemicals that may be required to operate equipment, as well as the troubling concept of "articles" that release chemicals under normal conditions.

Obligatory Certification of Electrical Products In Argentina: 10 years later
Silvia Diaz Monnier

Topics covered will be the evolution of the electrical safety certification system in Argentina and the requirements at present for electrical products commercialization in Argentina.


Halogen Free Electronics – An Overview
Randy Flinders

This presentation will provide an overview of the newly emerging “Halogen-Free Electronics” requirement and what it means to the ITE and Consumer Electronics industry.

Halogen-Free Electronics requirements have been flying below the radar, but if you supply components or products to ITE or consumer electronics manufacturers, this subject should be of interest to you. Topics will include a basic definition of Halogen-Free, some background and driving forces behind the Halogen-Free Electronics movement, and industry expectations for compliance. Halogen-Free standards will be discussed, including a status on the latest standard currently in development at IPC, as well as guidance on what manufacturers can do now to prepare for this requirement.

Global Mains Powering of Information Technology Equipment
Don Gies

This paper explores the different methods to connect information technology equipment (ITE) to the AC and DC mains in the global marketplace. It describes the difference in AC power systems around the world, including the voltages, phases, and plug configurations that vary country-to-country. It demonstrates single-phase and three-phase power systems used worldwide, including North American 120/240V, single-phase, three-wire power system, 120/208V three-phase and 230/400V three-phase systems. It describes IT power distribution systems, and how to design and test ITE for connecting to IT power distribution systems. Also, this paper discusses the different methods used for permanently connecting ITE to the mains in different regions of the world, and how to design ITE to accommodate the different installation methods.

Performance and calibration of touch current and protective conductor current equipment
German Gomez

Explain a technical procedure to verify the initial performance of touch current and protective conductor current network according to IEC 60990.

Explain a technical procedure to perform the routine calibration required by quality systems to touch current and protective conductor current network according to IEC 60990.

The NEW New Approach to technical harmonisation in Europe
Peter Kelleher

When the New Approach was originally decided upon by the European Council, it introduced an innovative approach to legislation and technical harmonisation in the European Union and it shaped the development of many commonly applied European Directives including the EMC, the R&TTE and the Low Voltage Directives. It also paved the way for CE Marking and acceptance of supplier’s declaration of conformity in Europe.

After more than twenty years the New Approach is undergoing an extensive revision which will influence future European directives and revisions to existing ones.

The presentation will discuss the background to the revision and examine in detail the practical impact to manufacturers and importers to the European Union as well as the timing of its implementation. I will highlight significant changes from current practices or common interpretations.

Safety Pre-testing simplifies NEBS compliance
Dave Lorusso

Do you want your product to fly through NEBS testing? Who doesn’t. In order to sell equipment to the Regional Bell Operating Companies (RBOCs), your product must comply with the NEBS requirements of Telcordia GR-63-CORE and GR-1089-CORE. Testing throughout the design process simplifies product development and helps assure equipment compliance to NEBS. This presentation provides guidance on how to simplify NEBS compliance through pre-testing.

Where did it come from?
Don Mader

A brief look at some requirements and how they were developed. Some involved rigorous science, some involved intuition and others relied on good guess work. This presentation will take a brief look at the following requirements: 1500-volt dielectric voltage withstand test, Mattress flame test, TV fire resistant material requirements, Construction requirements for fire sprinkler "O" rings, Steiner Tunnel, Leakage current and Plenum cable fire resistance.

A Treatise on Grounding of AC Electrical Systems and an Atypical Electrocution Case Study
Nosh Medora

In the United States, “grounded” and “grounding” are defined by the National Electrical Code (NEC), which is concerned with the safety of life and property. This paper presents information on grounded and grounding conductors in single phase and 3-phase service panels. It lists selected components in a typical service panel including the neutral terminal block and the ground terminal block.

This paper also presents potential reasons for ineffective grounding, and further presents how a fault condition can occur due to an ineffective safety ground which can possibly result in an electrocution hazard. It also presents reasons for fault conditions such as frayed or damaged insulation within the equipment resulting in exposed energized conductors making contact with the metal enclosure, the presence of a conductive foreign object bridging the gap between the hot terminal and the metal enclosure, and other reasons.

This paper further presents an unusual case study of an inadvertently ungrounded electric air compressor which was alleged to have resulted in an electrocution. Review of the plaintiffs’ report and preliminary electrical tests conducted by the authors indicated a probable different cause. Subsequently, the authors performed electrical tests using an IEC 60990 human body model (HBM) and confirmed that the alleged air compressor was probably not the cause of the electrocution. Further investigation revealed that a different electrical source was the probable cause of the electrocution.

Case Study – Conductive Contamination – Measuring the Leakage Resistance of a Single Fastener In Situ in a Transit System
Nosh Medora

Conductive contamination in electrical systems can result in leakage currents that may cause misoperation, electrochemical corrosion, and/or ignition of equipment, and possibly electrocution. One example of the deleterious effect of conductive contamination is in transit systems.

During normal operation of transit vehicles, currents drawn by traction motors in the vehicle cause a voltage to develop on the running rails, causing leakage currents to flow to ground over the rail fastener surfaces which may be contaminated with dirt and moisture. These leakage currents can cause extensive damage, including erosion of the rails, fasteners, and structural metals. The total leakage current in a system may be readily measured, and may be tens to hundreds of amperes. However, determining the electrical resistance of a selected fastener in situ requires measuring the leakage current of that individual fastener, which is extremely difficult since the fasteners are electrically connected by the low impedance of the continuously welded running rails.

This presentation presents a development procedure and system analysis to measure the leakage current of one fastener in situ in the Bay Area Rapid Transit (BART) system without any modification of the rails, and further presents computer simulations to optimize circuit parameters including test voltage and frequency.

Using the optimized parameters, a test instrument was developed using flexible toroidal current transducers to measure the leakage current of a single fastener in trackwork in the BART system without any modification of the rails or use of insulated joints. The proposed test instrumentation was bench tested, and the relatively high accuracy obtained in measuring leakage resistance of one fastener in place using the proposed test instrument, clearly demonstrates the feasibility of such an instrument.

Safety Type-Tests for Component Power Supplies and Component Transformers
Brian O'Connell

In addition to the typical series of Type Tests that are performed on component power supplies and/or component transformers, there are also some test requirements that are specific to each of the various information technology, medical, and laboratory product safety standards.

Component power supplies must also be compatible with local electric codes; there may be test requirements that are not in the targeted safety standard. These tests are found in a national version of the standard (typically delineated in the National Differences and Special National Conditions of the CB Report), or in local electric codes. Acceptable test technique and test materials are not always defined.

The paper will focus on the design and conduct of a type test to indicate conformity to specific safety requirements for a component power supply and for isolation component transformers. The repeat or addition of some type tests, based on the end-use installation and conditions of acceptability, will also be discussed.

A detailed discussion of the construction and performance requirements for power supplies and transformers, for the various standards, is NOT included.

Physical Body Parameter Calculations Based Upon Electrical Measurement
Peter E Perkins, PE

Analysis of electric shock effects in people depends entirely upon the body model used as the basis for the analysis.  The usual model has been developed for use under specific conditions; the conditions seem to get buried with time.  It would be helpful to get additional information such that models representing varying conditions could be developed for specific situations. 

Traditional circuit analysis quickly determines the current and voltage in each element of a circuit.  The use of complex variable analysis has long given way to SPICE like circuit simulators which provide the same results.  Unfortunately, the use of these new computer based methods do not give rise to broader analysis nor attempts to work backwards through the analysis to determine the circuit values when a measured output is in hand.

This paper develops the complex variable analysis (phasor analysis to EE’s) for the usual human body model then works backwards from measured body current & voltage measurements to determine the skin resistance and capacitance for several subjects under several conditions. 

The Future of Product Safety
Rich Pescatore

They said it couldn't be done - a safety standard built on the foundation of Hazard-Based Safety Engineering. But Rich Pescatore is currently leading the international effort to create just such a standard. It will be known as IEC 62368 and its scope will be Safety of Information and Communication Technology Equipment and Audio/Video Equipment. Mr. Pescatore will review the basis, the scope and the goals of this new standard. He will share his insight into the challenges being overcome to make this standard both accurate and useful, and he will describe the work being done to ensure it will be functional in the all important IECEE CB Scheme. You will walk away with the latest up-to-date progress being made on this work.

IECEE - The Worldwide System for Conformity Testing and Certification of Electrotechnical Equipment and Components
Pierre de Ruvo

In recognition of the need to facilitate international trade in electrical equipment, primarily intended for use in homes, offices, workshops, healthcare facilities and similar locations, for benefit of consumers, industries, authorities etc, and to provide convenience for manufacturers and other users of the services provided by various National Certification Bodies (NCBs), an international Scheme is operated by the IECEE (IEC System for Conformity testing and Certification of Electrotechnical Equipment and Components), known as the CB Scheme.

The Scheme is based on the principle of mutual recognition (reciprocal acceptance) by its members of test results for obtaining certification or approval at national level.

The Scheme is intended to reduce obstacles to international trade which arise from having to meet different national certification or approval criteria. Participation of the various NCBs within the Scheme is intended to facilitate certification or approval according to IEC standards.

Where national standards are not yet completely based on IEC standards, declared national differences will be taken into account; however, successful operation of the Scheme presupposes that national standards are reasonably harmonized with the corresponding IEC standards.

Use of the Scheme to its fullest extent will promote the exchange of information necessary in assisting manufacturers around the world to obtain certification or approval at national level.

The operating units of the Scheme are the NCBs accepted according to these Rules. Those NCBs employ testing laboratories also accepted according to the Rules, known as CB Testing Laboratories (CBTLs). A list of NCBs is published in the CB Bulletin.

The CB Scheme is based on the use of CB Test Certificates which provide evidence that representative specimens of the product have successfully passed tests to show compliance with the requirements of the relevant IEC standard.

A supplementary report providing evidence of compliance with declared national differences in order to obtain national certification or approval may also be attached to the CB Test Report.


Propagating Combustion Faults on Printed Wiring Boards
Gary Tornquist

This insidious type of fault can move along power traces on PCB’s combusting the epoxy material along the way. This paper develops a basic the thermal-electric model of the fault to explain feedback involved in the faults movement. The main inputs to the model, the electrical source energy and trace geometries are explored. From this understanding, appropriate design safeguards are qualitatively suggested.