IEC TR 62368-2:2011

IEC/TR 62368-2 ®
Edition 1.0 2011-06
TECHNICAL
REPORT
colour
inside
Audio/video, information and communication technology equipment –
Part 2: Explanatory information related to IEC 62368-1

IEC/TR 62368-2:2011(E)
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IEC/TR 62368-2 ®
Edition 1.0 2011-06
TECHNICAL
REPORT
colour
inside
Audio/video, information and communication technology equipment –
Part 2: Explanatory information related to IEC 62368-1

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XD
ICS 33.160.01; 35.020 ISBN 978-2-88912-542-5

– 2 – TR 62368-2  IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
AUDIO/VIDEO, INFORMATION AND
COMMUNICATION TECHNOLOGY EQUIPMENT –

Part 2: Explanatory information related to IEC 62368-1

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 62368-2, which is a technical report, has been prepared by subcommittee TC108: Safety
of electronic equipment within the field of audio/video, information technology and
communication technology.
TR 62368-2  IEC:2011(E) – 3 –
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
108/439/DTR 108/452/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
In this standard, the following print types are used:
– notes/explanatory matter: in smaller roman type (also in green if colour is available);
– tables and figures that are included in the rationale have linked fields (shaded in grey if
“field shading” is active).
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 62368 series can be found, under the general title Audio/video,
information and communication technology equipment, on the IEC website.
In this document, only those subclauses considered to need further background reference
information or explanation of their content to benefit the reader are included. Therefore, not
all numbered subclauses are cited. Unless otherwise noted, all references are to clauses,
subclauses, annexes, figures or tables are located in IEC 62368-1:2010.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 4 – TR 62368-2  IEC:2011(E)
AUDIO/VIDEO, INFORMATION AND
COMMUNICATION TECHNOLOGY EQUIPMENT –

Part 2: Explanatory information related to IEC 62368-1

Clause 0 Introduction – Principles of this product safety standard
Clause 0 is informational and provides a rationale for the normative clauses of
the standard.
0.5.7 Equipment safeguards during skilled person service conditions
Purpose: To explain the intent of requirements for providing safeguards against
involuntary reaction.
Rationale: By definition, a skilled person has the education and experience to identify all
class 3 energy sources to which he may be exposed. However, while servicing
one class 3 energy source in one location, a skilled person may be exposed to
another class 3 energy source in a different location.
In such a situation, either of two events is possible. First, something may cause
an involuntary reaction of the skilled person with the consequences of contact
with the class 3 energy source in the different location. Second, the space in
which the skilled person is located may be small and cramped, and inadvertent
contact with a class 3 energy source in the different location may be likely.
In such situations, this standard may require an equipment safeguard solely for
the protection of a skilled person while performing servicing activity.
___________
Clause 1 Scope
Purpose: To identify the purpose and applicability of this standard and the exclusions
from the scope.
Rationale: The scope excludes requirements for functional safety. Functional safety is
addressed in IEC 61508-1. Because the scope includes computers that may
control safety systems, functional safety requirements would necessarily
include requirements for computer processes and software. The TC108 experts
are experts in hardware safety, and have little or no expertise to properly
address functional safety requirements.
___________
Clause 3 Terms and definitions
Rationale is provided for definitions that deviate from IEV definitions or from
pilot standard definitions.
3.3.2.1 electrical enclosure
Source: IEV 195-06-13
Purpose: To support the concept of safeguards as used in this standard.
Rationale: The IEV definition is modified to use the term “safeguard” in place of the word
“protection”. The word “safeguard” identifies a physical “thing” whereas the
word “protection” identifies the act of protecting. This standard sets forth
requirements for use of physical safeguards and requirements for those
safeguards. The safeguards provide “protection” against injury from the
equipment.
3.3.5.1 basic insulation
Source: IEV 195-06-06
TR 62368-2  IEC:2011(E) – 5 –
Purpose: To support the concept of safeguards as used in this standard.
Rationale: The IEV definition is modified to use the term “safeguard” in place of the word
“protection”. The word “safeguard” identifies a physical “thing” whereas the
word “protection” identifies the act of protecting. This standard sets forth
requirements for use of physical safeguards and requirements for those
safeguards. The safeguards provide “protection” against injury from the
equipment.
3.3.5.2 double insulation
Source: IEV 195-06-08
Purpose: To support the concept of safeguards as used in this standard.
Rationale: See 3.3.5.1, basic insulation.
3.3.5.5 solid insulation
Source: IEC 60664-1:2007, 3.4
Purpose: To support the concept that safeguards are interposed between an energy
source and a body part.
Rationale: IEC 60664-1 defines insulation as material interposed between two conductive
parts. The IEC 60664-1 definition is modified by adding that insulation is also
“between a conductive part and a body part.” For safety purposes, solid
insulation is not only used between conductors, but is also used between a
conductor and a body part. For example, a Class II equipment employs solid
insulation in this manner.
3.3.5.6 supplementary insulation
Source: IEV 195-06-07
Purpose: To support the concept of safeguards as used in this standard.
Rationale: See 3.3.5.1, basic insulation.
3.3.6.6 restricted access area
Source: IEV 195-04-04
Purpose: To use the concept of “instructed persons” and “skilled persons” as used in this
standard.
Rationale: The IEV definition is modified to use the terms “instructed persons” and “skilled
persons” rather than “electrically instructed persons” and “electrically skilled
persons.”
3.3.7.8 reasonably foreseeable misuse
Source: ISO/IEC Guide 51:1999, definition 3.14
Purpose: To describe that the standard does not generally address foreseeable misuse.
Rationale: The scope excludes consideration of foreseeable misuse that might lead do an
injury. Misuse depends on personal objectives, personal perception of the
equipment, and the possible use of the equipment (in a manner not intended by
the manufacturer) to accomplish those personal objectives. Equipment within
the scope of this standard ranges from small handheld equipment to large,
permanently installed equipment. There is no commonality among the
equipment for readily predicting human behaviour leading to misuse of the
equipment and resultant injury. Manufacturers are encouraged to consider
reasonably foreseeable misuse of equipment and provide safeguards, as
applicable, to prevent injury in the event of such misuse. (Not all reasonably
foreseeable misuse of equipment results in injury or potential for injury.)
3.3.8.1 instructed person
Source: IEV 826-18-02
Purpose: To use the terms used in this standard.

– 6 – TR 62368-2  IEC:2011(E)
Rationale: The IEV definition is modified to use the terms “energy sources”, “skilled
person”, and “precautionary safeguard”. The definition is made stronger by
using the term “instructed” rather than “advised”.
3.3.8.3 skilled person
Source: IEV 826-18-01
Purpose: To use the terms used in this standard.
Rationale: The IEV definition is modified to use the phrase “to reduce the likelihood of”.
IEC 62368-1 does not use the word “hazard”.
3.3.14.5 prospective touch voltage
Source: IEV 195-05-09
Purpose: To properly identify electric shock energy source voltages.
Rationale: The IEV definition is modified to delete “animal”. The word “person” is also
deleted as all of the requirements in the standard are with respect to persons.
3.3.14.10 working voltage
Source: IEC 60664-1:2007, definition 3.5
Purpose: To distinguish between r.m.s. working voltage and peak working voltage.
Rationale: The IEC 60664-1 definition is modified to delete “r.m.s”. IEC 62368-1 uses both
r.m.s. working voltage and peak working voltage; each term is defined.
3.3.15.2 class II construction
Source: IEC 60335-1:2001, 3.3.11
Purpose: Although the term is not used in the standard, for completeness, it was decided
to retain this definition.
Rationale: The word “appliance” is changed to “equipment”.
____________
Clause 4 General requirements
Purpose: To explain how to investigate and determine whether or not safety is involved.
Rationale: In order to establish whether or not safety is involved, the circuits and
construction are investigated to determine whether the consequences of
possible fault conditions would lead to an injury. Safety is involved if, as a
result of a single fault condition, the consequences of the fault lead to a risk of
injury.
If a fault condition should lead to a risk of injury, the part, material, or device
whose fault was simulated may comprise a safeguard.
Rationale is provided for questions regarding the omission of some traditional
requirements appearing in other safety standards. Rationale is also provided
for further explanation of new concepts and requirements in this standard.
functional insulation
Purpose: To explain why the standard has no requirements for functional insulation.
Rationale: This standard does not include requirements for functional insulation. By its
nature, functional insulation does not provide a safeguard function against
electric shock or electrically-caused fire and therefore may be faulted.
Obviously, not all functional insulations are faulted as this would be
prohibitively time-consuming. Sites for functional insulation faults must be
based upon physical examination of the equipment, upon the electrical
schematic.
Note that basic and reinforced insulation may also serve as functional
insulation, in which case the insulation is not faulted.

TR 62368-2  IEC:2011(E) – 7 –
functional components
Purpose: To identify the conditions for consideration of functional components as
safeguards.
Rationale: This standard does not include requirements for functional components. By
their nature, individual functional components do not provide a safeguard
function against electric shock, electrically-caused fire, thermal injury, etc., and
therefore may be candidates for fault testing. Obviously, not all functional
components are faulted as this would be prohibitively time-consuming.
Candidate components for fault testing must be based upon physical
examination of the equipment, upon the electrical schematic diagrams, and
whether a fault of that component might result in conditions for electric shock,
conditions for ignition and propagation of fire, conditions for thermal injury, etc.
As with all fault-condition testing (Clause B.4), upon faulting of a functional
component, there shall not be any safety consequence (for example, a benign
consequence), or a basic, supplementary, or reinforced safeguard shall remain
effective.
In some cases, a pair of functional components may comprise a safeguard. If
the fault of one of the components in the pair is mitigated by the second
component, then the pair must be designated as a double safeguard. For
example, if two diodes are employed in series to protect a battery from reverse
charge, then the pair must comprise a double safeguard and the components
must be limited to the manufacturer and part number actually tested. A second
example is that of an X-capacitor and discharge resistor. If the discharge
resistor should fail open, then the X-capacitor will not be discharged.
Therefore, the X-capacitor value must not exceed the ES2 limits specified for a
charged capacitor. Again, the two components comprise a double safeguard
and the values of each component must be limited to values for ES1 under
normal operating conditions and the values for ES2 under single fault
conditions.
4.1.1 Application of requirements and acceptance of materials, components
and subassemblies
Purpose: To accept components as safeguards.
Rationale: This standard includes requirements for safeguard components. A safeguard
component is a component specifically designed and manufactured for both
functional and safeguard parameters. Examples of safeguard components are
capacitors complying with IEC 60384-14 and other IEC component standards.

– 8 – TR 62368-2  IEC:2011(E)
4.3.2 Safeguards for protection of an ordinary person

IEC  1339/11
4.3.3 Safeguards for protection of an instructed person

IEC  1340/11
TR 62368-2  IEC:2011(E) – 9 –
4.3.4 Safeguards for protection of a skilled person
IEC  1341/11
4.4.3 Composition of a safeguard
Purpose: To specify design and construction criteria for a single safeguard (basic,
supplementary, or reinforced) comprised of more than one element, for
example, a component or a device.
Rationale: Safeguards need not be a single, homogeneous component. Indeed, some
parts of this standard require a single safeguard be comprised of two or more
elements. For example, for thin insulation, two or more layers are required to
qualify as supplementary insulation. Another example is protective bonding and
protective earthing, both of which are comprised of wires, terminals, screws,
etc.
If a safeguard is comprised of two or more elements, then the function of the
safeguard must not be compromised by a failure of any one element. For
example, if a screw attaching a protective earthing wire should loosen, then the
current-carrying capacity of the protective earthing circuit may be
compromised, making its reliability uncertain.
4.4.5 Safeguard robustness
Purpose: To require safeguards to be robust.
Rationale: Safeguards must be sufficiently robust to withstand the rigors of expected use
throughout the equipment lifetime. Robustness requirements are specified in
the various clauses.
_____________
Clause 5 Electrically-caused injury
Purpose: Clause 5 classifies electrical energy sources and provides criteria for
determining the energy source class of each conductive part. The criteria for
energy source class include the source current-voltage characteristics,
duration, and capacitance. Each conductive part, whether current-carrying or
not, or whether earthed or not, shall be classed ES1, ES2, or ES3 with respect
to earth and with respect to any other simultaneously accessible conductive
part.
– 10 – TR 62368-2  IEC:2011(E)
5.2.1 Electrical energy source classifications
Source: IEC/TS 60479-1 and IEC 61201
Purpose: To define the line between hazardous and non-hazardous electrical energy
sources for normal and abnormal operating conditions.
Rationale: The effect on persons from an electric source depends on the CURRENT
through the human body. The effects are described in IEC/TS 60479-1.
Purpose: ES1 may be accessible to an ordinary person with no safeguards
Rationale: IEC/TS 60479-1:2005 (see Figures 20 and 22, Tables 11 and 13); zone AC-1
and zone DC-1; usually no reaction (Figure 1 and Figure 2, Table 1 and
Table 2 in this standard).
Purpose: ES2 may be accessible to an instructed person with no safeguards and to an
ordinary person under a fault condition of a basic safeguard.
Rationale: IEC/TS 60479-1:2005 (see Figures 20 and 22; Tables 11 and 13); zone AC-2
and zone DC-2; usually no harmful physiological effects (see Figure 1 and
Figure 2, Table 1 in this standard).
Purpose: ES3 is not accessible to an ordinary person nor to an instructed person under
normal conditions or under a fault condition of a safeguard. Parts and circuits
classed ES3 may be accessible to a skilled person.
Rationale: IEC/TS 60479-1; zone AC-3 and zone DC-3; harmful physiological effects may
occur (see Figure 1 and Figure 2, Table 1 and Table 2 in this standard).

TR 62368-2  IEC:2011(E) – 11 –

ms
10 000
a b
c c c
1 2 3
5 000
AC-4.1
2 000
AC-4.2
AC-4.3
1 000
AC-1 AC-2 AC-3 AC-4
0,1 0,2 0,5 1 2 5 10 20 50 100 200 500 1 000 2 000 5 000 10 000 mA
Body current I
B IEC  1000/05
Figure 1 – Conventional time/current zones of effects
of a.c. currents (15 Hz to 100 Hz) on persons for a current path corresponding
to left hand to feet (see IEC/TS 60479-1:2005, Figure 20)
Table 1 – Time/current zones for a.c. 15 Hz to 100 Hz
for hand to feet pathway (see IEC/TS 60479-1:2005, Table 11)
Zones Boundaries Physiological effects
AC-1 up to 0,5 mA curve a Perception possible but usually no startle reaction
AC-2 0,5 mA up to curve b Perception and involuntary muscular contractions likely but usually no
harmful electrical physiological effects
AC-3 Curve b and above Strong involuntary muscular contractions. Difficulty in breathing.
Reversible disturbances of heart function. Immobilisation may occur.
Effects increasing with current magnitude. Usually no organic damage
to be expected.
a
AC-4 Above curve c Pathophysiological effects may occur such as cardiac arrest,
breathing arrest, and burns or other cellular damage. Probability of
ventricular fibrillation increasing with current magnitude and time.
c – c AC-4.1 Probability of ventricular fibrillation increasing up to about
1 2
5 %.
c – c AC-4.2 Probability of ventricular fibrillation up to about 50 %.
2 3
Beyond curve c AC-4.3 Probability of ventricular fibrillation above 50 %.
a
For durations of current flow below 200 ms, ventricular fibrillation is only initiated within the vulnerable period if
the relevant thresholds are surpassed. As regards ventricular fibrillation this figure relates to the effects of
current which flows in the path left hand to feet. For other current paths the heart current factor has to be
considered.
Duration of current flow  t
– 12 – TR 62368-2  IEC:2011(E)

ms
10 000
a b
c c c
1 2 3
5 000
DC-4.1
DC-4.2
2 000
DC-4.3
1 000
DC-1 DC-2 DC-3 DC-4
0,1 0,2 0,5 1 2 5 10 20 50 100 200 500 1 000 2 000 5 000 10 000 mA
Body current I
B
IEC  1002/05
Figure 2 – Conventional time/current zones of effects of d.c. currents on persons for a
longitudinal upward current path (see IEC/TS 60479-1:2005, Figure 22)
Table 2 – Time/current zones for d.c. for hand to feet pathway
(see IEC/TS 60479-1:2005, Table 13)
Zones Boundaries Physiological effects
DC-1 Up to 2 mA curve a Slight pricking sensation possible when making, breaking or rapidly
altering current flow.
DC-2 2 mA up to curve b Involuntary muscular contractions likely, especially when making,
breaking or rapidly altering current flow, but usually no harmful
electrical physiological effects
DC-3 curve b and above Strong involuntary muscular reactions and reversible disturbances of
formation and conduction of impulses in the heart may occur,
increasing with current magnitude and time. Usually no organic
damage to be expected.
a
DC-4 Above curve c Pathophysiological effects may occur such as cardiac arrest,
breathing arrest, and burns or other cellular damage. Probability of
ventricular fibrillation increasing with current magnitude and time.
c – c
DC-4.1 Probability of ventricular fibrillation increasing up to about
1 2
5 %.
c – c DC-4.2 Probability of ventricular fibrillation up to about 50 %.
2 3
Beyond curve c DC-4.3 Probability of ventricular fibrillation above 50 %.
a
For durations of current flow below 200 ms ventricular fibrillation is only initiated within the vulnerable period if
the relevant thresholds are surpassed. As regards ventricular fibrillation this figure relates to the effects of
current which flows in the path left hand to feet and for upward current. For other current paths the heart
current factor has to be considered.

Duration of current flow  t
TR 62368-2  IEC:2011(E) – 13 –
The effects for an injury increas continuously with the energy transferred to the body. To
demonstrate this principle Figure 1 and Figure 2 in this standard (see IEC/TS 60479-1:2005,
Figures 20 and 22) are transferred into a graph: effects = (f) energy (see Figure 3 in this
standard).
Effects
Effects
EEnneerrggyy ssoouurrccee
AC/DC -4
AC/DC -4
AACC//DDCC --33
aa)) TThhrreesshhoolldd ooff
ppeerrcceeppttiioonn
b) Threshold of let go
AACC//DDCC --22 b) Threshold of let go
cc)) TThhrreesshhoolldd ooff

vveennttrriiccuullaarr ffiibbrriillllaattiioonn

AACC//DDCC --11
aa bb c
c
Energy
Energy
IEC  1342/11
Figure 3 – Illustration that limits depend on both voltage and current
Within the standard only the limits for Zone 1 (green) and Zone 2 (yellow) will
be specified.
Curve “a” (limit of Zone 1) will be the limit for parts accessible by an ordinary
person during normal use.
Curve “b” (limit of Zone 2) will be the limit for parts accessible by an ordinary
person during (or after) a single fault.
It was found to be not acceptable to go to the limits of either Zone 3 or 4.
In the standard three (3) zones are described as electrical energy sources.
This classification is as follows:
– electrical energy source 1 (ES1): levels are of such a value that they do not
exceed curve “a” (threshold of perception) of Figure 1 and Figure 2 in this
standard (see IEC/TS 60479-1:2005, Figures 20 and 22).
– electrical energy source 2 (ES2): levels are of such a value that they exceed
curve “a”, but do not exceed curve “b” (threshold of let go) of Figure 1 and
Figure 2 in this standard (see IEC/TS 60479-1:2005, Figures 20 and 22).
– electrical energy source 3 (ES3): levels are of such a value that they exceed
curve “b” of Figure 1 and Figure 2 in this standard (see IEC/TS 60479-
1:2005, Figures 20 and 22).
– 14 – TR 62368-2  IEC:2011(E)
5.2.2.2 Steady-state voltage and current limits
Table 4 – Electrical energy source limits for d.c. and low frequency a.c. currents
Source: IEC/TS 60479-1, Dalziel, Effect of Wave Form on Let-Go Currents; AIEE
Electrical Engineering Transactions, Dec 1943, Vol 62.
Purpose: Current values for ES Sources.
Rationale: The current limits of Table 4 line 1 and 2 are derived from curve a and b,
Figure 1 and Figure 2 in this standard (see IEC/TS 60479-1:2005, Figures 20
and 22).
The basis for setting limits for combined a.c. and d.c. touch current is from the
work of Dalziel which provides clear data for men, women and children. Since
we are working with consumer appliances under this standard we need to
provide protection for children, which are generally considered the most severe
case.
The formulas of IEC 62368-1:2010, Table 4 addresses the Dalziel
investigations.
Table 5 – Electrical energy source limits for d.c. and low frequency a.c. voltages
Source: IEC 60950-1 and IEC 61201:2007(see Table 3 in this standard)
Purpose: Voltage values for ES sources.
Rationale: In most cases the electrical power source is a voltage source. Therefore it is
practical for the design and testing of electrical equipment to specify voltage
limits.
The values chosen in the table are for dry conditions only.
Typically, physically larger people in the population have lower internal body
resistance because of their larger cross sectional area. Physically small people
in the population generally have higher internal body resistance. Some
measurements of body impedances show that the body impedance is not
greatly influenced by the body weight. Therefore there is not sufficient
correlation between the body weight (children or adults) and the physiological
current values corresponding to a particular effect.
– ES-1 and ES-2 voltage limits are taken from IEC 60950-1, based on
experience.
– ES-1 voltage limits correspond to the limits of SELV circuits of IEC 60950-1
and to Table A.1 of IEC/TS 61201:2001 environmental situation 3 (dry).
– ES-2 voltage limits correspond to the limits of TNV circuits of IEC 60950-1
and to Table A.1 of IEC/TS 61201:2001 environmental situation 3 (dry)
“single fault.”
The basis for setting limits for combined a.c. and d.c. touch current is from the
work of Dalziel which provides clear data for men, women and children. Since
we are working with consumer appliances under this standard we need to
provide protection for children, the worst case.
The formulas of IEC 62368-1:2010, Table 5 addresses the Dalziel
investigations.
TR 62368-2  IEC:2011(E) – 15 –
Table 3 – Limits for steady-state voltages (see IEC 61201:2007)
Environmental situation No fault Single fault Two faults
1 0 V 0 V 16 V a.c.
35 V d.c.
2 16 V a.c. 33 V a.c. Not applicable
b
35 V d.c. 70 V d.c.
a a
3 33 V a.c. 55 V a.c. Not applicable
b b
70 V d.c. 140 V d.c.
4 Special applications
a 2
For a non-grippable part with a contact area less than 1 cm , limits are 66 V and 80 V respectively.
b
For charging a battery, limits are 75 V and 150 V.

Table 6 – Electrical energy source limits for medium and high frequency voltage and
current
Source: IEC/TS 60479-2 and IEC/TS 60479-1
Purpose: Voltage values for ES Sources with higher frequencies.
Rationale: The effect of a.c. current with higher frequencies (above 100 Hz) is
documented in IEC/TS 60479-2. With increasing frequency an increasing
current has the same effect to the human body (Figures 9 and 12 of
IEC/TS 60479-2:2007). For high frequency currents of about 100 mA burns
may occur. Therefore the maximum HF current limit is specified to 100 mA. The
formula used for the ES1 limits of the HF current is already used in IEC 60215
and in IEC 60950-1. The body impedance falls with increasing frequency. The
effect is documented in IEC/TS 60479-1. Therefore the voltage limits has a
different formula than the formula for the current.
5.2.2.3 Capacitance limits
Table 7 – Electrical energy source limits for a charged capacitor
Source: IEC/TR 61201:2007 (Annex A)
Purpose: Limits for capacitances.
Rationale: Where the energy source is a capacitor, the energy source class is determined
from both the charge voltage and the capacitance. The capacitance limits are
derived from IEC 61201:2007.
The values for ES2 are derived from Table A.2 (IEC 61201:2007).
The values for ES1 are calculated by dividing the values from Table A.2
(IEC 61201:2007) by two (2).
While Table 4 in this standard shows a value of 60 kV for 0,133 nF capacitor,
because this value results in an energy greater than 350 mJ (using ½ CV
formula), it was changed to 50 kV.

– 16 – TR 62368-2  IEC:2011(E)
Table 4 – Limit values of accessible capacitance (threshold of pain) –
(IEC 61201:2007)
U(V) U(kV) C(nF)
C(μF)
70 42,4 1 8,0
78 10,0 2 4,0
80 3,8 5 1,6
90 1,2 10 0,8
100 0,58 20 0,4
150 0,17 40 0,2
200 0,091 60 0,133
250 0,061
300 0,041
400 0,028
500 0,018
700 0,012
5.2.2.4 Single pulse limits
Table 8 – Voltage limits for single pulses
Table 9 – Current limits for single pulses
Source: IEC/TS 60479-1:2005
Purpose: Values for ES Sources of single pulses.
Rationale: For ES1 the limit of single pulse should not exceed the ES-1 steady state
voltage limits for d.c. voltages.
For ES2 the voltage limits have been calculated by using the d.c. current
values of curve b Figure 2 in this standard (IEC/TS 60479-1:2005, Figure 22)
and the resistance values of Table 10, column for 5 % of the population (see
Table 5 in this standard).
The current limits of single pulses in Table 9 for ES-1 levels are from curve a
and for ES-2 are from curve b of Figure 2 in this standard (IEC/TS 60479-
1:2005, Figure 22).
TR 62368-2  IEC:2011(E) – 17 –
Table 5 – Total body resistances R for a current path hand to hand, d.c.,
T
for large surface areas of contact in dry condition

Values for the total body resistance R (Ω)
T
that are not exceeded for
Touch voltage
V
5 % of the 50 % of the 95 % of the
population population population
25 2 100 3 875 7 275
50 1 600 2 900 5 325
75 1 275 2 275 4 100
100 1 100 1 900 3 350
125 975 1 675 2 875
150 875 1 475 2 475
175 825 1 350 2 225
200 800 1 275 2 050
225 775 1 225 1 900
400 700 950 1 275
500 625 850 1 150
700 575 775 1 050
1 000 575 775 1 050
Asymptotic value 575 775 1 050

NOTE 1 Some measurements indicate that the total body resistance R for the current path hand to foot
T
is somewhat lower than for a current path hand to hand (10 % to 30 %)
NOTE 2  For living persons the values of R correspond to a duration of current flow of about 0,1 s
T
For longer durations R values may decrease (about 10 % to 20 %) and after complete rupture
T
of the skin R approaches the initial body resistance R
T o
NOTE 3 Values of R are rounded to 25 Ω
T
5.2.2.5 Limits for repetitive pulses
Table 10 – Electrical energy source limits for repetitive pulses
Source: IEC/TS 60479-2 and IEC/TS 60479-1
Purpose: To define current and voltage limits for repetitive pulses.
Rationale: For repetitive pulses with a pulse-off time less than 3 s the steady state peak
values of Table 4 are used.
For repetitive pulses with a pulse-off time more than 3 s the limit values of
single pulses from Table 8 (voltage) or Table 9 (current) are used.
5.2.2.6 Ringing signals
Source: EN 41003
Purpose: Limits for analogue telephone network ringing signals.
Rationale: For details see rationale for Annex H. Where the energy source is an analogue
telephone network ringing signal as defined in Annex H, the energy source
class is taken as ES2 (as in IEC 60950-1:2005, Annex M).

– 18 – TR 62368-2  IEC:2011(E)
5.2.2.7 Audio signals
Source: IEC 60065:2001; IEC 62368-1:2010, Annex E
Purpose: To establish limits for touch voltages for audio signals.
Rationale: The proposed limits for touch voltages at terminals involving audio signals that
may be contacted by persons have been extracted without deviation from
IEC 60065:2001. Reference: IEC 60065:2001, 9.1.1.1a). Under single fault
conditions, 10.1 of IEC 60065:2001 does not permit an increase in acceptable
touch voltage limits.
The proposed limits are quantitatively larger than the accepted limits of Tables
5 and 6, but are not considered dangerous for the following reasons:
– the output is measured with the load disconnected (worst case load);
– defining the contact area of connectors and wiring is very difficult due to
complex shapes. The area of contact is considered small due to the
construction of the connectors;
– normally, it is recommended to the user, in the instruction manual provided
with the equipment, that all connections be made with the equipment in the
“off” condition. In this case we could consider the user as an instructed
person;
– in addition to being on, the equipment would have to be playing some
program at a high output with the load disconnected to achieve the
proposed limits (although possible, highly unlikely). Historically, no known
cases of injury are known for amplifiers with non-clipped output less than
71 V r.m.s;
– the National Electrical Code (USA) permits accessible terminals with
maximum output voltage of 120 V r.m.s.
5.3.2 Protection of an ordinary person
Ordinary person
ES1
Basic
Safeguard ES2
Supplementary Basic
Safeguard ES3
Safeguard
IEC  1343/11
Figure 4 – Safeguards between an energy source and an ordinary person
5.3.2.1 Safeguards between energy source ES1 and an ordinary person
Source: IEC/TS 60479-1
Purpose: No requirement for a safeguard.
Rationale: Because there is usually no reaction of the human body when touching ES1,
access is permitted (IEC/TS 60479-1; zone AC-1 and zone DC-1). See Figure 4
in this standard.
TR 62368-2  IEC:2011(E) – 19 –
5.3.2.2 Safeguards between energy source ES2 and an ordinary person
Source: IEC/TS 60479-1
Purpose: At least one equipment safeguard.
Rationale: Because there may be a reaction of the human body when touching ES2,
protection is required. But one safeguard is sufficient because there are usually
no harmful physiological effects when touching ES2 (IEC/TS 60479-1; zone
AC-2 and zone DC-2). See Figure 4 in this standard.
5.3.2.3 Safeguards between energy source ES3 and an ordinary person
Source: IEC/TS 60479-1
Purpose: At least two safeguards, one basic and one supplementary.
Rationale: Because harmful physiological effects may occur when touching ES3, (IEC/TS
60479-1; zone AC-3 and zone DC-3), protection is required including after a
fault of one safeguard. See Figure 4 in this standard.
5.3.3 Protection of an instructed person
Instructed person
ES1
Behaviour
ES2
Safeguard
Supplementar Basic
ES3
Safeguard Safeguard
IEC  1344/11
Figure 5 – Safeguards between an energy source and an instructed person
5.3.3.1 Safeguards between ES1 or ES2 and an instructed person
Source: IEC/TS 60479-1
Purpose: No requirement for a safeguard.
Rationale: For ES1: because there is usually no reaction of the human body when
touching ES1 access is permitted (IEC/TS 60479-1; zone AC-1 and zone
DC-1). (See Figure 5 in this standard.)
For ES2: An instructed person is instructed that there may be a reaction of the
human body when touching ES2 but no harmful physiological effects may occur
when touching ES2 (IEC/TS 60479-1; zone AC-2 and zone DC-2). (See
Figure 5 in this standard).
– 20 – TR 62368-2  IEC:2011(E)
5.3.3.2 Safeguards between ES3 and an instructed person
Source: IEC/TS 60479-1
Purpose: At least two safeguards, one basic and one supplementary.
Rationale: Because harmful physiological effects may occur when touching ES3,
(IEC/TS 60479-1; zone AC-3 and zone DC-3), a protection is required including
after a fault of one safeguard. (See Figure 5 in this standard.)
5.3.4 Protection of a skilled person

ES1
ES2
Skill
Safeguard ES3
IEC  1345/11
Figure 6 – Safeguards between energy sources and a skilled person
5.3.4.1 Safeguards between ES1 or ES2 and a skilled person
Source: IEC/TS 60479-1
Purpose: No requirement for a safeguard.
Rationale: For ES1: Because there is usually no reaction of the human body when
touching ES1 access is permitted (IEC/TS 60479-1; zone AC-1 and zone DC-
1). (See Figure 6 in this standard.)
For ES2: A skilled person has the knowledge that there may be a reaction of
the human body when touching ES2, but that there are no harmful
physiological effects when touching ES2 (IEC/TS 60479-1; zone AC-2 and
zone DC-2). (See Figure 6 in this standard.)
5.3.4.2 Safeguards between ES3 and a skilled person
Purpose: Unintentional contact has to be prevented.
Rationale: A skilled person has the knowledge that there may be harmful physiological
effects when touching ES3. (See Figure 6 in this standard.)
5.3.5 Safeguards between energy sources
5.3.5.2 Safeguards between ES1, ES2 and ES3
Purpose: At least one basic safeguard between ES1 and ES2.
Rationale: ES1 could be accessible for an ordinary person; ES2 should not therefore, the
same protection as for ES2 applies (see 5.3.2.2).

TR 62368-2  IEC:2011(E) – 21 –
Purpose: At least two safeguards between ES1 and ES3, one basic and one
supplementary.
Rationale: ES1 could be accessible for an ordinary person; ES3 should not, even after a
single fault, therefore the same protection as for ES3 (see 5.3.2.3).
Purpose: Example of determination of ES1 class for interconnected sources.
Rationale: ES1 circuits must be examined for voltage and current for both normal
operating condition and single fault condition. If the voltage does not exceed
the ES1 limit or, under single fault conditions, the ES2 limit, then the current
does not need to be measured. Several examples are provided.

Example A, normal operating condition

EXAMPLE A
AAA
normal operating conditions
volts d.c.
40 V40 V40 V  ddd.c.c.c.
A B C D E
A 0 40 0 0 n/a
BBB
B 40 0 0 0 n/a
C 0 0 0 40 n/a
D 0 0 40 0 n/a
CCC
E n/a n/a n/a n/a n/a
40 V40 V40 V  ddd.c.c.c.
DDD
EEE
IEC  1346/11
All voltages are within ES1 limits. Terminals A, B, C, D, and E may be accessible. If A, B, C, or D is
connected to E, the results are the same.

Example B, single fau
...