OVERVIEW OF CHANGES FOR IEC :2014 FOURTH EDITION

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1 OVERVIEW OF CHANGES FOR IEC :2014 FOURTH EDITION December 2014

2 In February, the International Electrotechnical Commission (IEC) published the fourth edition of IEC , a collateral standard that provides the requirements for essential performance and basic safety in the presence of electromagnetic disturbances. Requirements for documentation, technical descriptions, user information, in addition to emissions limitation and susceptibility performance, are outlined in the standard. This article presents some of the major changes introduced by the IEC in the fourth edition of IEC with a focus on testing for emissions and susceptibility. Electromagnetic Environments A very important change to recognize in the fourth edition with regards to electromagnetic (EM) environments is the removal of the category of life-supporting equipment. The standard has now introduced EM environments of intended use. Intended use is defined in the collateral standard, IEC , as use for which a product, process or service is intended according to the specifications, instructions and information provided by the manufacturer (IEC , 2012). The introduction of these EM environments helps to clarify the applicable test limits for emissions limitations and test levels that are to be applied during susceptibility testing. The two major categories of EM environments are professional healthcare facilities and home healthcare. Professional healthcare facilities are those facilities that have attending medical staff on hand such as hospitals, dental offices and intensive care and surgery rooms except near high-frequency surgical equipment. Home healthcare environment is defined in IEC as a dwelling place in which a patient lives or other places where patients are present, excluding professional healthcare facility environments where operators with medical training are continually available when patients are present (IEC , 2010). A third EM environment that has been included is special environments. Special environments are those areas that do not fall under professional healthcare facilities or home healthcare locations. These locations may have emissions limits, susceptibility test levels or test methods that are different from those specified for the professional healthcare facility environment and the home healthcare environment. These special locations include heavy industrial plants or medical treatment areas with high powered medical electrical equipment like short wave therapy equipment. Emissions Requirements Unlike its predecessor, the fourth edition has removed CISPR 15 as an option to show compliance for a device that provides lighting features. These products now have to be tested to CISPR 11 requirements. Products that are simple motor-operated devices with no electronics can still be tested to CISPR 14-1 and all other products in professional healthcare facilities and home healthcare facilities, excluding aircraft, are tested to CISPR 11. Devices that are transported by air are subject to emissions requirements in accordance with ISO 7137, which has requirements equivalent to DO-160G Category M. If the device can be used in other means of transportation then the appropriate emissions standards should be used, for example applying CISPR 25 for motor vehicles. In professional healthcare facilities, Harmonics (IEC ) and Flicker (IEC ), are tests that are only required if medical electrical equipment or systems will be connected directly to the public mains network. These tests are mandatory for home 2

3 healthcare facilities that operate off AC mains power. It should be noted that IEC does limit the applicability to devices that operate on 230 Vac, single phase, or 400 Vac three-phase power configurations. Flicker testing is limited to an operating frequency of 50 Hz. Susceptibility Requirements Unlike emissions testing which did not undergo major changes, susceptibility requirements to ensure a device is not susceptible to events that could be encountered during normal use in the intended environment have changed rather significantly. The following will present a summary of those changes. It is always recommended to read the standard for complete details of the test in question. Electrostatic Discharge (ESD) ESD test levels were increased for both air and contact type discharges. Air discharges are conducted on those surfaces which are not metallic. Contact discharges are conducted both directly and indirectly. Direct contact discharges are performed directly on metallic portions of a product while indirect contact discharges are conducted on the vertical and horizontal coupling planes which represent adjacent or stacked products respectively. Tests levels for contact discharges increased from ±6kV to ±8kV. Air discharges increased from ±8kV to ±15kV. This includes patient coupling ports but this test is not performed with the ports connected to simulators or connected to an artificial hand. Radiated RF Electromagnetic Fields Radiated RF Electromagnetic Fields or RF susceptibility test levels are now specified based on the intended use environment. For professional healthcare facilities the test level of 3 V/m did not change from the previous edition of the standard. For home healthcare environments, the test level increased to 10 V/m. Tests are still conducted in accordance with IEC In addition to the standard RF susceptibility test, which is conducted from 80 MHz to 2.7 GHz, the fourth edition added a new test to simulate proximity to wireless communication equipment. This test is required for both professional healthcare facilities and home healthcare environments and the test levels do not vary based on the intended use environment because the levels being simulated from wireless devices would be the same at either location. The test frequencies, modulation and test levels are shown in Table 1. Table 1: RF susceptibility test levels Test Frequency (MHz) 385 Pulse modulation 18 Hz 450 FM ±5 khz deviation 1 khz sine** 710, 745, 780 Pulse modulation 217 Hz 810, 870, 930 Pulse modulation 18 Hz 1720, 1845, 1970, 2450 Modulation* Susceptibility Test Level (V/m) Pulse modulation 217 Hz 5240, 5500 Pulse modulation 217 Hz * carrier shall be modulated using a 50% duty cycle square wave signal ** 50% pulse modulation at 18 Hz may be used Electrical Fast Transients (EFT) EFT did not undergo test level changes. ±2kV levels on AC and DC power ports and ±1kV levels on signal

4 input/signal output (SIP/SOP) lines are still required. However the test repetition frequency applied has increased from 5 khz to 100 khz. According to IEC , 100 khz is more representative of the actual repetition frequency that equipment would experience in an installation. DC power port testing is only required on ports that will be permanently connected to lines greater than 3 meters in length. SIP/SOP lines also are only tested if greater than 3 meters in length. Surge Immunity For AC powered devices, the fourth edition has the same requirements as its predecessor. DC-powered devices where power lines are permanently connected and greater than 3 meters in length will need to meet the same test levels as AC-powered devices; ±1kV line-to-line and ±2kV line-to-ground. New to the fourth edition are surges to SIP/SOP lines that are directly connected to outdoor cables. If a product has this type of interface then tests at ±2kV line-to-ground will be required. IEC remains the basic standard that defines the specific test methods. Electrical transient conduction along supply lines New to the fourth edition are transient tests on DC input power ports in accordance with ISO These transient tests are applied to devices installed in passenger cars and light commercial vehicles including ambulances fitted with 12 V electrical systems or commercial vehicles including ambulances fitted with 24 V electrical systems. These tests are not intended for equipment installed in professional healthcare facilities. For details, it is recommended to consult ISO however, a summary of the impulses are listed in Table 2. Table 2: EFT Tests levels for DC input power ports in IEC ed. 4.0 Test Pulse Applied Impulse Level (Volts) Power System (Volts) (battery voltage) or 24 2a or 24 2b b a a b b Conducted disturbances induced by RF fields The section on conducted RF disturbances added new requirements based on the location of intended use. In the professional healthcare environment, the test levels applied increase from 3 Vrms to 6 Vrms in the Industrial Scientific and Medical (ISM) bands. For home healthcare environments the test levels increase to the same amount in the ISM bands and also the higher levels apply in the amateur radio bands. DC Power ports need only be tested for permanently connected power lines that are greater than 3 meters in length. In addition to the increase in test levels in both the ISM and amateur radio bands, the fourth edition also added an exemption to SIP/SOP ports that are less than 3 meters in length (note that the FDA has not accepted this clause and testing is required on any length SIP/SOP cable, see Extent of Recognition at fda.gov/scripts/cdrh/cfdocs/cfstandards/detail. cfm?standard_identification_no=32630 for more information). 4

5 Power Frequency Magnetic Fields The fourth edition has increased the test levels for power frequency magnetic fields tenfold. The new tests levels are 30 A/m rather than 3 A/m from third edition. This new test level is required for both professional and home healthcare facilities. Unlike the third edition, the new requirements are only applied to devices with magnetically sensitive components, for example reed relays disk drives, etc. In addition, new warnings are provided which indicate that if the medical electrical equipment is to be used closer than 15 cm to the source of the power frequency magnetic field, the test level is to be adjusted as needed to ensure it is representative of fields at the closer distance. Voltage Dips and Interruptions The fourth edition has introduced testing at multiple phase angles for the half-cycle, 100% voltage dip (0% residual voltage during the test). Testing is to occur at each phase angle with a 45-degree step size (0, 45, 90, 135, 180, 225, 270 and 315 ). All other tests still require a single phase angle test at the 0 crossing. Fourth edition removed the requirement of the 40%, five-cycles dip and replaced it with a one-cycle, 100% voltage dip. Voltage dips are only required on devices that are rated less than 16A/phase. Voltage interruptions for equipment rated greater than 16A/ phase-only requires a single interruption at any phase angle and if the medical electrical equipment has a multiphase power configuration then the interruption is conducted on all phases dropped simultaneously at any phase angle. For multiphase equipment that is rated less than 16A/phase, all phases are interrupted simultaneously. In all cases, if the device operates at both 50 Hz and 60 Hz, then the cycles are adjusted accordingly for each power line frequency, for example 250 cycles for 50 Hz and 300 cycles for 60 Hz, each resulting in a five-second interruption in input power. Input Power and Frequencies during testing The third edition required that tests such as EFT and Surge be performed at both the highest and lowest rated AC voltages when a medical electrical device included a rated voltage range or employed an auto switching power supply with a rated voltage range. In the fourth edition this requirement was removed. A table was added to clarify the test voltage and frequency required for both emissions and susceptibility testing. For all tests, with the exception of Voltage Dips and Short Interruptions, Harmonics and Flicker testing can be conducted at any one power input voltage. For Harmonics and Flicker, if the device is single phase and is rated between 220Vac and 240Vac, testing is conducted at 230Vac. For three phase equipment rated between 380Vac and 415Vac, the device is tested at 400Vac. All other voltages do not require testing of Harmonics and Flicker mainly due to the fact that the standards IEC and IEC only specify limits in these voltage ranges and other ranges do not have defined limits. 5

6 For Voltage Dips and Short Interruptions, if the rated range is less than 25% of the lowest input voltage then testing can be conducted at any single rated input voltage. In all other cases testing is conducted at the minimum and maximum rated voltages. Essentially, a rated input of 100Vac - 240Vac would require testing at the minimum and maximum voltages but a rated input of 200Vac - 240Vac would only require testing at a single voltage within that range. The only exception would be where the medical electrical equipment power input voltage is varied by a change in a transformer tap, then testing only needs to be conducted at one tap setting regardless of the range of the transformer taps. The line frequency for testing for all tests except Harmonics, Flicker and Power Frequency Magnetic Fields can be set to any one of the rated frequencies. For Harmonics, testing can be conducted at either 50 Hz or 60 Hz and Flicker is only tested for devices rated with a line frequency of 50 Hz (e.g. a rating of 50/60 Hz would require testing at 50 Hz). Power Frequency Magnetic Fields is tested at either 50 Hz or 60 Hz as long as the test frequency is the same as the operating frequency of the medical electrical equipment at the time of the test; e.g. medical electrical equipment is operating at 50 Hz, the test frequency of the magnetic coil is 50 Hz. What s Next? There have been some extensive changes to the fourth edition that can greatly impact product design from an EMC perspective. From defined use environments to new tests and documentation requirements, the standard is a working improvement in patient safety. It is important to review the tests, requirements and documentation details with your test lab to ensure that you fully comply with all the requirements that have been put in place. It should also be noted that SC62A, the IEC committee that is responsible for IEC is already working on Amendment 1 to the fourth edition. Author: Bob DeLisi Bob DeLisi is a project lead and certifier in the UL Telecommunication Certification Body program in the Consumer Technology division at UL s Melville facility. He has been with UL for 25 years and has been involved in all facets of the UL EMC business from testing to lab management. He participates on ANSI Accredited Standards Committee C63 and is the chair of Subcommittee 8 for Medical Devices and actively participates on Subcommittee 1 (Techniques and Development) and Subcommittee 6 (Accreditation/Conformity Assessment). He is also a member of the IECEE s Committee of Testing Laboratories Expert Task Force, CLT-EFT 10 for EMC. DeLisi is the vice chair for the Long Island IEEE EMC Society Chapter. DeLisi holds a bachelors degree in electrical engineering and is a NARTE Certified EMC laboratory engineer. This article is for general information purposes only and is not intended to convey legal or other professional advice. 6