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PD IEC/TS 62996:2017 Industrial electroheating and electromagnetic processing equipment. Requirements on touch currents, voltages and electric fields from 1 kHz to 6 MHz, 2017
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- CONTENTS
- FOREWORD
- INTRODUCTION
- 1 Scope
- 2 Normative references
- 3 Terms and definitions
- 4 Organization and use of this document
- 5 Prospective source voltage limits
- 6 Assessment of the source impedance
- 7 Touching and access considerations [Go to Page]
- 7.1 General
- 7.2 Primary contact areas
- 7.3 Special protective gloves, footwear and clothing
- 7.4 External metallic objects and tools
- 7.5 Considerations for the secondary contact area assessment
- 8 Impedances of parts of the body, and touch current densities [Go to Page]
- 8.1 General
- 8.2 The equivalent circuit of skin and parts of the body
- Figures [Go to Page]
- Figure 1 – Complex impedances of various parts of the body, 1 kHz to 6 MHz
- 8.3 Touch current density consideration for large contact areas
- 9 Capacitively coupled currents in the body due to an external electric field or insulated live part [Go to Page]
- 9.1 General and measurement frequency
- 9.2 Determination of the capacitance
- 9.3 Assessment of the electric field and use of reference level data
- 9.4 Measurement methods and limiting values [Go to Page]
- 9.4.1 Simplified measurement of the prospective current in the parts of the body
- 9.4.2 More accurate method for determination of currents in the parts of the body
- 9.4.3 Limiting touch current values
- 10 Electric shock – immediate nerve and muscle reactions [Go to Page]
- 10.1 General
- 10.2 Touch current limits – immediate nerve and muscle reactions
- 11 Electric shock – local overheating and burns of parts of the body [Go to Page]
- 11.1 General and initial thermal conditions
- Figure 2 – Maximum allowed touch and touch currents, 1 kHz to 100 kHz,immediate nerve and muscle electric shock
- 11.2 Awareness, perception and withdrawal [Go to Page]
- 11.2.2 Heat sensing nerves exist only in the skin region, and thus not in the interior of for example fingers. Conditions where such interior heating occurs while the skin sensing is insufficient for perception are dealt with in 11.3.
- 11.2.3 The perception conditions for hazard calculations are skin temperature rises of at least 3 K over 5 s to 10 s and 5 K over 20 s or less. These times then include the time for withdrawal. The high alternative value 10 s applies if the touching p...
- 11.3 Long-term tissue overheating
- 12 Requirements and risk group classification [Go to Page]
- 12.1 General
- 12.2 Conditions for the touch current limits up to 100 kHz
- 12.3 Requirements related to skin temperature rises and times of awareness, perception and withdrawal [Go to Page]
- 12.3.1 Skin heat capacity considerations
- 12.3.2 Skin temperature considerations
- 12.4 Risk level categorisation as function of the prospective contact voltage
- 12.5 Additional protection: residual current protective devices (RCDs)
- 13 Non-sinusoidal touch currents
- Tables [Go to Page]
- Table 1 – Maximally allowed skin power density per surface area,under various conditions of withdrawal
- 14 Warning marking and risk group classifications [Go to Page]
- Figure 3 – Warning markings
- Annex A (informative) Examples of calculations [Go to Page]
- A.1 General
- A.2 Skin heating
- Table A.1 – Comparison of impedances of parts of the body, using the equivalentcircuits in IEC 60990:2016 and in this document
- Table A.2 – Moist skin, finger and overall heating rate at 50 V overall effective voltage, using equivalent circuits in IEC 60990:2016 and this document
- Table A.3 – Wet skin, finger and overall heating rate at 50 V overall effective voltage,using this document, with halved skin impedances comparedwith Table A.2
- Table A.4 – Effective contact voltage limits for the moist skin examples in Table A.2
- Table A.5 – Effective contact voltage limits for the wet skin examples in Table A.3
- A.3 Examples of tissue heating conditions [Go to Page]
- A.3.1 With 1 500 mm2 fingerskin area, i.e. gripping
- A.3.2 With the maximal fingerskin area 230 mm2
- Annex B (informative) Rationales, references and volunteer studies in the non-thermal case [Go to Page]
- B.1 Background and observations
- B.2 Discussion of Figure B.1
- Figure B.1 – Maximum allowed touch and touch currents in various standards, 1 kHzto 100 kHz, immediate nerve and muscle electric shock
- B.3 A volunteer study at 11 kHz sinusoidal conditions [Go to Page]
- B.3.1 Experimental setup and data
- B.3.2 Discussion and analysis of the experimental data
- Figure B.2 – Setup for touch current and voltage measurements with indexand middle fingers on 50 mm2 flat conductors
- B.4 Contact/touch current data from standards and other published documents
- B.5 Reference levels for the external electric field
- B.6 Prospective touch voltage limits
- B.7 Perception and pain in relation to risk levels
- Figure B.3 – Current measuring circuit for unweighed touch current,from IEC 60990:2016
- B.8 Remarks on the slope of the curves for frequencies higher than 10 kHz
- B.9 Remarks on the touch current levels above 100 kHz in ICNIRP and IEEE specifications
- Annex C (informative) Additional information and rationales – skin data and impedances of parts of the body [Go to Page]
- C.1 Skin anatomy
- Figure C.1 – Human skin anatomy (from Wikipedia)
- C.2 Comparative calculation procedure for wet skin impedances
- C.3 Some data for dry skin
- C.4 Frequency dependence of the body tissue electrical conductivities
- C.5 Calculations for Table 1
- Figure C.2 – Average electrical conductivities for homogeneous body modellingfrom 10 Hz to 10 MHz (from EN 50444:2008)
- Table C.1 – Comparison of complex impedances of moist and wet fingers
- Bibliography [Go to Page]