In this subclause measurements of current through networks simulating the impedance of the human body are referred to as measurements of TOUCH CURRENT.
Except for application of 5.1.8.2, these requirements do not apply to equipment intended to be supplied by only a DC MAINS SUPPLY.
5.1.1 General
Equipment shall be so designed and constructed that neither TOUCH CURRENT nor PROTECTIVE CONDUCTOR CURRENT is likely to create an electric shock hazard.
Compliance is checked by testing in accordance with 5.1.2 to 5.1.7 inclusive, and, if relevant, 5.1.8 (see also 1.4.4).
However, if it is clear from a study of the circuit diagrams of either STATIONARY PERMANENTLY
CONNECTED EQUIPMENT or STATIONARY PLUGGABLE EQUIPMENT TYPEB, that has a PROTECTIVE
EARTHING CONDUCTOR, that the TOUCH CURRENT will exceed 3,5 mA r.m.s., but that the
PROTECTIVE CONDUCTOR CURRENT will not exceed 5 % of input current, the tests of 5.1.5, 5.1.6
and 5.1.7.1 a) are not made.
NOTE In the above case, the requirement of 5.1.7.1 b) continues to apply.
5.1.2 Configuration of equipment under test (EUT) 5.1.2.1 Single connection to an a.c. mains supply
Systems of interconnected equipment with individual connections to the AC MAINS SUPPLY shall
have each piece of equipment tested separately. Systems of interconnected equipment with one common connection to the AC MAINS SUPPLY shall be treated as a single piece of
equipment. See also 1.4.10 regarding the inclusion of optional features.
NOTE Systems of interconnected equipment are specified in more detail in Annex A of IEC 60990.
5.1.2.2 Redundant multiple connections to an a.c. mains supply
Equipment that is designed for multiple connections to the ACMAINS SUPPLY, only one of which
is required at a time, shall be tested with only one connection.
5.1.2.3 Simultaneous multiple connections to an a.c. mains supply
Equipment requiring power simultaneously from two or more AC MAINS SUPPLIES shall be tested
with all AC MAINS SUPPLIES connected.
The total TOUCH CURRENT through all PROTECTIVE EARTHING CONDUCTORS that are connected to
each other and to earth is measured. IEC 60950-1 : 2005
60950-1 IEC:2005 – 351 –
A PROTECTIVE EARTHING CONDUCTOR that is not connected within the equipment to other
earthed parts in the equipment shall not be included in the above tests. If an a.c. power source has such a PROTECTIVE EARTHING CONDUCTOR it shall be tested separately according to
5.1.2.1 (see also 5.1.7.2).
5.1.3 Test circuit
Equipment is tested using the test circuit in Figure 5A (for single-phase equipment to be connected only to a star TN or TT power distribution system) or Figure 5B (for three-phase equipment to be connected only to a star TN or TT power distribution system) or where appropriate, another test circuit from Figures 7, 9, 10, 12, 13 or 14 of IEC 60990.
The use of a test transformer for isolation is optional. For maximum protection, a test transformer for isolation (T in Figures 5A and 5B) is used and the main protective earthing terminal of the EUT is earthed. Any capacitive leakage in the transformer shall then be taken into account. As an alternative to earthing the EUT, the test transformer secondary and the EUT are left floating (not earthed) in which case capacitive leakage in the transformer need not be taken into account.
If transformer T is not used, the EUT and the test circuitry shall not be earthed. The EUT is mounted on an insulating stand, and appropriate safety precautions are taken in view of the possibility of the BODY of the equipment being at a HAZARDOUS VOLTAGE.
Equipment to be connected to an IT power distribution system is tested accordingly (see Figures 9, 10 and 12 of IEC 60990). Such equipment may also be connected to a TN or TT power distribution system without further test.
Single-phase equipment intended to be operated between two line conductors is tested using a three-phase test circuit such as Figure 5B.
If it is inconvenient to test equipment at the most unfavourable supply voltage (see 1.4.5), it is permitted to test the equipment at any available voltage within the tolerance of RATED VOLTAGE
or within the RATED VOLTAGE RANGE, and then calculate the results.
IEC 60950-1 : 2005 IS 13252 (Part 1) : 2010
60950-1 IEC:2005 – 353 – L N PE T p1 L N PE e B A s p2 (Polarity) (Polarity) Point of connection to AC MAINS SUPPLY TELECOMUNICATION NETWORK connection port (not connected)
(Earthing conductor) Measuring network Optional test transformer for isolation (Test switch) EUT
NOTE This figure is derived from Figure 6 of IEC 60990.
Figure 5A – Test circuit for touch current of single-phase equipment on a star TN or TT power supply system
T p1 L1 N PE e B A s p2 (Polarity) (Polarity) (Test switch) L2 L3 L1 L2 L3 N PE EUT Point of connection to AC MAINS SUPPLY TELECOMUNICATION NETWORK connection port (not connected)
(Earthing conductor) Measuring network Optional test transformer for isolation
NOTE This figure is derived from Figure 11 of IEC 60990.
Figure 5B – Test circuit for touch current of three-phase equipment on a star TN or TT power supply system
IEC 60950-1 : 2005
60950-1 IEC:2005 – 355 –
5.1.4 Application of measuring instrument
Tests are conducted using one of the measuring instruments in Annex D, or any other circuit giving the same results.
Terminal B of the measuring instrument is connected to the earthed (neutral) conductor of the supply (see Figure 5A or 5B).
Terminal A of the measuring instrument is connected as specified in 5.1.5.
For an accessible non-conductive part, the test is made to metal foil having dimensions of 100 mm by 200 mm in contact with the part. If the area of the foil is smaller than the surface under test, the foil is moved so as to test all parts of the surface. Where adhesive metal foil is used, the adhesive shall be conductive. Precautions are taken to prevent the metal foil from affecting the heat dissipation of the equipment.
NOTE 1 The foil test simulates hand contact.
Accessible conductive parts that are incidentally connected to other parts are tested both as connected and disconnected parts.
NOTE 2 Incidentally connected parts are described in more detail in Annex C of IEC 60990.
5.1.5 Test procedure
For equipment having a protective earthing connection or a FUNCTIONAL EARTHING connection,
terminal A of the measuring instrument is connected via measurement switch "s" to the main protective earthing terminal of the EUT, with the earthing conductor switch "e" open.
The test is also conducted, on all equipment, with terminal A of the measuring network connected via measurement switch "s" to each unearthed or non-conductive accessible part and each unearthed accessible circuit, in turn, with the earthing conductor switch "e" closed. Additionally:
− for single-phase equipment, the tests are repeated in reverse polarity (switch "p1");
− for three-phase equipment, the tests are repeated in reverse polarity (switch "p1") unless the equipment is sensitive to phase sequence.
When testing three-phase equipment, any components used for EMC purposes and connected between line and earth are disconnected one at a time; for this purpose, groups of components in parallel connected through a single connection are treated as single components. Each time a line-to-earth component is disconnected the sequence of switch operations is repeated.
NOTE Where filters are normally encapsulated, it may be necessary to provide an unencapsulated unit for test or to simulate the filter network.
For each placement of the measuring instrument, any switches in the PRIMARY CIRCUIT and
likely to be operated in normal use are open and closed in all possible combinations.
After applying each test condition, the equipment is restored to its original condition, that is without fault or consequential damage.
IEC 60950-1 : 2005 IS 13252 (Part 1) : 2010
60950-1 IEC:2005 – 357 –
5.1.6 Test measurements
Either the r.m.s. value of the voltage, U2, is measured using the measuring instrument of Figure D.1, or the r.m.s. value of the current is measured using the measuring instrument of Figure D.2.
The D.1 instrument gives a more accurate measurement than the D.2 instrument if the waveform is non-sinusoidal and the fundamental frequency exceeds 100 Hz.
Alternatively, the peak value of the voltage, U2, is measured using the measuring instrument described in Clause D.1.
If the voltage, U2, is measured using the measuring instrument described in Clause D.1, the following calculation is used:
TOUCH CURRENT (A) = U2 / 500
NOTE Although r.m.s. values of TOUCH CURRENT have traditionally been measured, peak values provide better correlation with the response of the human body to non-sinusoidal current waveforms.
None of the values measured in accordance with 5.1.6 shall exceed the relevant limits in Table 5A, except as permitted in 2.4 (see also 1.5.6 and 1.5.7) and 5.1.7.
Table 5A – Maximum current
Type of equipment measuring instrument Terminal A of connected to: Maximum TOUCH CURRENT mA r.m.s.a Maximum PROTECTIVE CONDUCTOR CURRENT All equipment Accessible parts
and circuits not connected to protective earth b
0,25 –
HAND-HELD 0,75 –
MOVABLE (other than
HAND-HELD, but including
TRANSPORTABLE EQUIPMENT)
3,5 –
STATIONARY,
PLUGGABLE TYPE A
3,5 – All other STATIONARY
EQUIPMENT
– not subject to the conditions of 5.1.7
3,5 – – subject to the conditions
of 5.1.7
Equipment main protective earthing terminal
(if any)
– 5 % of input current a If peak values of TOUCH CURRENT are measured, the maximum values are obtained by multiplying the r.m.s.
values in the table by 1,414.
b Some unearthed accessible parts are covered in 1.5.6 and 1.5.7 and the requirements of 2.4 apply. These may be different from those in 5.1.6.
5.1.7 Equipment with touch current exceeding 3,5 mA 5.1.7.1 General
TOUCH CURRENT measurement results exceeding 3,5 mA r.m.s. are permitted for the following
equipment having a main protective earthing terminal:
IEC 60950-1 : 2005
60950-1 IEC:2005 – 359 – − STATIONARYPERMANENTLY CONNECTED EQUIPMENT;
− STATIONARY PLUGGABLE EQUIPMENT TYPE B;
− STATIONARY PLUGGABLE EQUIPMENT TYPEA with a single connection to the AC MAINS SUPPLY,
and provided with a separate protective earthing terminal in addition to the main protective earthing terminal, if any (see 2.6.4.1). The installation instructions shall specify that this separate protective earthing terminal be permanently connected to earth;
NOTE 1 The above equipment is not required to be installed in a RESTRICTED ACCESS LOCATION. However, the requirement to be STATIONARY EQUIPMENT is more onerous than the similar requirements in 2.3.2.3 a) because the potential hazard is greater.
− MOVABLE or STATIONARY PLUGGABLE EQUIPMENT TYPEA for use in a RESTRICTED ACCESS LOCATION, with a single connection to the AC MAINS SUPPLY, and provided with a separate
protective earthing terminal in addition to the main protective earthing terminal, if any (see 2.6.4.1). The installation instructions shall specify that this separate protective earthing terminal be permanently connected to earth;
NOTE 2 The limitation of use to a RESTRICTED ACCESS LOCATION is more onerous than the similar requirements in 2.3.2.3 a) because the potential hazard is greater.
− STATIONARY PLUGGABLE EQUIPMENT TYPEA with simultaneous multiple connections to the AC MAINS SUPPLY, intended to be used in a location having equipotential bonding (such as
a telecommunication centre, a dedicated computer room or a RESTRICTED ACCESS LOCATION). A separate additional protective earthing terminal shall be provided on the
equipment. The installation instructions shall require all of the following:
• the building installation shall provide a means for connection to protective earth; and • the equipment is to be connected to that means; and
• a SERVICE PERSON shall check whether or not the socket-outlet from which the
equipment is to be powered provides a connection to the building protective earth. If not, the SERVICE PERSON shall arrange for the installation of a PROTECTIVE EARTHING CONDUCTOR from the separate protective earthing terminal to the protective earth wire in
the building.
NOTE 3 In Finland, Norway and Sweden, TOUCH CURRENT measurement results exceeding 3,5 mA r.m.s. are permitted only for the following equipment:
- STATIONARY PLUGGABLE EQUIPMENT TYPEA that
• is intended to be used in a RESTRICTED ACCESS LOCATION where equipotential bonding has been applied, for example, in a telecommunication centre,
• has provision for a permanently connected PROTECTIVE EARTHING CONDUCTOR, and • is provided with instructions for the installation of that conductor by a SERVICE PERSON; - STATIONARY PLUGGABLE EQUIPMENT TYPEB;
- STATIONARY PERMANENTLY CONNECTED EQUIPMENT.
NOTE 4 In Denmark, TOUCH CURRENT measurement results exceeding 3,5 mA r.m.s. are permitted only for
PERMANENTLY CONNECTED EQUIPMENT and PLUGGABLE EQUIPMENT TYPEB.
If the result of the TOUCH CURRENT measurement on any of the above equipments exceeds
3,5 mA r.m.s., the following requirements a) and b) apply, and also, if relevant, those in 5.1.7.2.
a) The r.m.s. PROTECTIVE CONDUCTOR CURRENT shall not exceed 5 % of the input current per
line under normal operating conditions. If the load is unbalanced, the largest of the three line currents shall be used for this calculation.
IS 13252 (Part 1) : 2010 IEC 60950-1 : 2005
60950-1 IEC:2005 – 361 –
To measure the PROTECTIVE CONDUCTOR CURRENT, the procedure for measuring TOUCH CURRENT is used but the measuring instrument is replaced by an ammeter of negligible
impedance; and
b) one of the following labels, or a label with similar wording, shall be affixed adjacent to the equipment AC MAINS SUPPLY connection:
WARNING
HIGH LEAKAGE CURRENT EARTH CONNECTION ESSENTIAL
BEFORE CONNECTING SUPPLY
WARNING
HIGH TOUCH CURRENT EARTH CONNECTION ESSENTIAL
BEFORE CONNECTING SUPPLY
Compliance is checked by inspection and measurement.
5.1.7.2 Simultaneous multiple connections to the supply
The following applies to EUT tested in accordance with 5.1.2.3. If the result of the total TOUCH
CURRENT measurement exceeds 3,5 mA r.m.s., the test is repeated with each ACMAINS SUPPLY
and its PROTECTIVE EARTHING CONDUCTOR connected one at a time, with the other AC MAINS
SUPPLIES, including their PROTECTIVE EARTHING CONDUCTORS, disconnected. However, if two
connections to the AC MAINS SUPPLY are inseparable, for example, connections for a motor and
its control circuits, they shall both be energized for a repeat test. NOTE It is not expected that the EUT will operate normally during this test.
If the result of the TOUCH CURRENT measurement for any of the repeat tests exceeds 3,5 mA r.m.s., the requirements of 5.1.7.1 a) apply to that connection to the ACMAINS SUPPLY.
For calculating 5 % of the input current per line, the input current from the ACMAINS SUPPLY,
measured during the repeat test, is used.
5.1.8 Touch currents to telecommunication networks and cable distribution systems and from telecommunication networks
NOTE In this subclause, references to "TELECOMMUNICATION NETWORK connection ports" (or telecommunication ports) are intended to cover those connection points to which a TELECOMMUNICATION NETWORK is intended to be attached. Such references are not intended to include other data ports, such as those commonly identified as serial, parallel, keyboard, game, joystick, etc.
5.1.8.1 Limitation of the touch current to a telecommunication network or to a cable distribution system
The TOUCH CURRENT from equipment supplied from the AC MAINS SUPPLY to a TELECOM- MUNICATION NETWORK or a CABLE DISTRIBUTION SYSTEM shall be limited.
Compliance is checked using the test circuit detailed in 5.1.3.
The tests are not applied to equipment where the circuit to be connected to a
TELECOMMUNICATION NETWORK or a CABLE DISTRIBUTION SYSTEM is connected to a protective
earthing terminal in the equipment; the TOUCH CURRENT from the EUT to the
TELECOMMUNICATION NETWORK or the CABLE DISTRIBUTION SYSTEM is considered to be zero.
IEC 60950-1 : 2005
60950-1 IEC:2005 – 363 –
For equipment having more than one circuit to be connected to a TELECOMMUNICATION
NETWORK or a CABLE DISTRIBUTION SYSTEM, the test is applied to only one example of each type
of circuit.
For equipment that has no main protective earthing terminal, the earthing conductor switch "e", if connected to a FUNCTIONAL EARTHING terminal on the EUT, is left open. Otherwise
it is closed.
Terminal B of the measuring instrument is connected to the earthed (neutral) conductor of the supply. Terminal A is connected via the measurement switch "s" and the polarity switch "p2" to the TELECOMMUNICATION NETWORK or CABLE DISTRIBUTION SYSTEM connection port.
For single-phase equipment, the test is made in all combinations of the polarity switches "p1" and "p2".
For three-phase equipment, the test is made in both positions of polarity switch "p2". After applying each test condition, the equipment is restored to its original operating state. Test measurements are made using one of the measuring instruments of Annex D as described in 5.1.6.
None of the values measured in accordance with 5.1.8.1 shall exceed 0,25 mA r.m.s.
5.1.8.2 Summation of touch currents from telecommunication networks
NOTE Annex W explains the background to 5.1.8.2.
An EUT that provides TELECOMMUNICATION NETWORK connection ports for connection of
multiple items of other telecommunication equipment, shall not create a hazard for USERS and
TELECOMMUNICATION NETWORK SERVICE PERSONS due to summation of TOUCH CURRENT.
In these requirements, abbreviations have the following meanings:
− I1 is the TOUCH CURRENT received from other equipment via a TELECOMMUNICATION NETWORK at a telecommunication port of the EUT;
− ∑I1 is the summation of TOUCH CURRENTS received from other equipment at all such
telecommunication ports of the EUT;
− I2 is the TOUCH CURRENT due to the ACMAINS SUPPLY of the EUT.
It shall be assumed that each telecommunication port receives 0,25 mA (I1) from the other equipment, unless the actual current from the other equipment is known to be lower.
The following requirements, a) or b) as applicable, shall be met:
a) EUT with earthed telecommunication ports
For an EUT in which each telecommunication port is connected to the main protective earthing terminal of the EUT, the following items 1), 2) and 3) shall be considered:
IS 13252 (Part 1) : 2010 IEC 60950-1 : 2005
60950-1 IEC:2005 – 365 – 1) If ∑I1 (not including I2) exceeds 3,5 mA:
− the equipment shall have provision for a permanent connection to protective earth in addition to the PROTECTIVE EARTHING CONDUCTOR in the power supply cord of PLUGGABLE EQUIPMENT TYPEA or PLUGGABLE EQUIPMENTB; and
− the installation instructions shall specify the provision of a permanent connection to protective earth with a cross-sectional area of not less than 2,5 mm2, if
mechanically protected, or otherwise 4,0 mm2; and
− one of the following labels, or a label with similar wording, shall be affixed adjacent to the permanent earth connection. It is permitted to combine this label with the label in 5.1.7.1 b).
WARNING
HIGH LEAKAGE CURRENT EARTH CONNECTION ESSENTIAL
BEFORE MAKING
TELECOMMUNICATION NETWORK CONNECTIONS
WARNING
HIGH TOUCH CURRENT EARTH CONNECTION ESSENTIAL
BEFORE MAKING
TELECOMMUNICATION NETWORK CONNECTIONS
2) ∑I1 plus I2 shall comply with the limits in Table 5A (see 5.1.6).
3) If relevant, such equipment shall comply with 5.1.7. The value of I2 shall be used to calculate the 5 % input current limit per phase specified in 5.1.7.
Compliance with item a) is checked by inspection and, if necessary, by test.
If the equipment has provision for a permanent protective earth connection in accordance with item 1) above, it is not necessary to make any measurements, except that I2 shall comply
with the relevant requirements of 5.1.
TOUCH CURRENT tests, if necessary, are made using the relevant measuring instrument