Source: https://www.zes.com/en/Products/Compliance-Test-Systems/LMG-Test-Suite
Timestamp: 2019-04-22 10:56:08+00:00

Document:
The LMG Test Suite is a ZES ZIMMER developed software, used together with the LMG Power Analyzers to perform EMC compliance tests in accordance with the currently valid versions of the IEC/EN 61000-3-2/-12 standards for harmonic emissions and the IEC/EN 61000-3-3/-11 standards for flicker disturbance. The software further supports measurements of standby power according to IEC 62301:2011 & EN 50564 as well as measurements of as per ECE R-10.4 Annex 11 (electromagnetic compatibility of vehicles). The LMG600 itself performs the harmonic analysis and flicker measurement according to the IEC/EN 61000-4-7 and 61000-4-15 standards.
Compliance tests with the LMG Test Suite can be carried out either online, while directly linked with the measurement hardware, or offline, using stored data records. Each measurement data record is accompanied with the basic electrical properties of the Equipment Under Test (RMS values of voltage and current, active, reactive and apparent power, power factor, harmonic distortion, etc.) to enhance the meaningfulness of the information and to avoid incorrect allocations. The measurement results and the limit values (either fixed or product-specific) defined in the standards are also presented graphically.
The system uses the LMG’s proven precision power measurement technology. All ZES ZIMMER power analyzers measure with particularly great reliability and precision. A fast Ethernet interface (Gbit) guarantees smooth communication and data transfer with the test system.
The LMG Test Suite can quickly help to identify the cause of a negative compliance test result. All measurements can be displayed and evaluated in the frequency and time domain. All harmonic frequencies can be isolated and examined throughout the test to assist with localizing the problem. In addition, all data can be passed on to third-party applications for additional analysis in full resolution, using the clipboard or file export.
The LMG Test Suite supports all AC power sources available on the market that fulfil the requirements of the CE standards to be tested. This provides maximum flexibility to the user. In particular, the user can continue using an AC source that they may have already in possession and thus avoid additional investments. Calibration of the source specifically for CE testing is not necessary as the test system monitors the compliance to the specified source parameters. For instance, the system analyzes the source’s voltage harmonics and presents them graphically. This ensures independence from the distortion and voltage stability of the source. Any problems from this side of the test structure are thus reliably excluded.
All results are documented in clear, comprehensive PDF test reports. Alongside the appointed measurement values, all data regarding the measurement equipment, test structure and settings -such as type designations, serial numbers and information on the calibration and traceability- is also integrated into the test reports. Of course, the reports can be supplemented with additional customer-specific information and design elements, in order to avoid unnecessary post-editing outside the system.
In the last two decades the power quality of the public electrical grid has become a serious concern, as electronic and power electronic devices have become standard equipment into households as well as commercial environments. Especially power electronic converters can draw significant harmonic currents from the AC mains leading to inefficient power transfer and burdening of the neutral wire.
At the same time the grid voltage often suffers of fluctuations due to high inrush currents caused by electric motors, or electronic devices. These voltage disturbances do not only affect the quality of the grid voltage, but also cause flicker, a repetitive change over time in the magnitude of the luminous flux of a light source. Flicker itself, whether visible or invisible, is a cause of discomfort for people who operate in environments where it is present.
In today’s power grids it is essential that phenomena such as harmonic current emissions and flicker disturbance are regulated and minimized. This is the scope of a large part of the IEC 61000 EMC standard family. These standards are issued in an international level from the International Electrotechnical Commission (IEC) and are reviewed and harmonized by local organizations that represent either single countries, or wider geographical regions.
The European Union is particularly demanding when it comes to electromagnetic compatibility, requiring from products that are intended for sale and distribution in its territory to bear the “CE” marking, meaning that they comply with the EMC Directive. The European Committee for Electrotechnical Standardization (Cenelec) commonly reviews the IEC international standards before they become European (EN) standards. The IEC and EN versions of the standards are not by definition identical despite the fact that it often happens to be so. The EN standards are the only ones relevant with CE marking.
Compliance testing according to the EN IEC 61000 series of standards is therefore crucial, for every manufacturer of electric and electronic equipment who intends to distribute their products into the European Union and the European Free Trade countries.
Another important matter that every electronics manufacturer must nowadays look after is the power efficiency of their devices and especially the watts that these devices consume when in standby mode. The EN 50564 standard, as derived from the IEC 62301, defines the procedures for measurement of low power on electrical and electronic household and office equipment.
The following table shows the standards supported by the LMG Test Suite, as well as the upcoming versions and their current state of implementation into the software.
ZES ZIMMER, as a manufacturer of precision power measurement technology, is represented in the international standards committee. As a result, all changes in standards are incorporated into our test systems.
77A/929/CDV, accepted by 100% but not yet published.
Modern electrical and electronic equipment can inject significant harmonic components into the public supply system. The scope of the IEC 61000-3-2 and IEC 61000-3-12 standards, is the limitation of these harmonic emissions in order to improve electromagnetic compatibility and voltage quality in the grid.
This standard refers to equipment under test (EUT) with input current of maximum 16 A per phase. Some general requirements include that the power input of the EUT may be connected to 220/380 V, 230/400 V or 240/415 V systems operating at 50 or 60 Hz.
Further equipment not specified as belonging to Class B, C or D is classified as Class A equipment.
According to each equipment class, different limits and test conditions may apply. The LMG Test Suite foresees selection of the proper equipment class in the test settings, with references to the paragraphs of the standard where the corresponding limits and procedure are described.
The power source that the circuit employs must comply with the requirements described in §A.2. For single phase measurements the same circuit applies if the 2 of 3 phases are ignored. In the software, operation of 1 or 3 phase EUT is clearly selectable.
The LMG600 power analyzer is designed to perform measurements of harmonics according to the EN IEC 61000-4-7 standard. It is the user’s task to control the type test conditions in Annex B according to the nature of the EUT and select the applicable limits. These are given to LMG Test Suite as inputs before the test. During the test, the LMG Test Suite carries out the measurement procedure described in §6.3.2 of EN IEC 61000-3-2 and applies the corresponding conditions and limits to the measurement.
At the same time, besides the measurement of the harmonic currents, the instrument measures the voltage at the EUT connection terminals and the software checks whether this complies with the requirements of §A.2. The software can carry out the tests either with grouping of harmonics or without, therefore supporting both newer and older versions of the standard. Lastly, the software can plot certain current harmonics over time. Although this measurement is not required by the standard, it is very helpful in discovering the causes of harmonic emission on certain orders that might lead to non-compliance.
According to the standard, the test report may be based on information supplied by the manufacturer to a testing facility, or be a document recording details of the manufacturer’s own tests. It includes all relevant information for the test conditions, the test observation period, and, when applicable for establishing the limits, the active power or fundamental current and power factor.
This standard refers to equipment under test (EUT) with input current exceeding 16 A and up to 75 A per phase, intended to be connected to public low-voltage distribution systems of nominal voltage up to 240 V (1-ph 2-3 wires) or 690 V (3-ph, 3-4 wires) and nominal frequency of 50 or 60 Hz.
The EN IEC 61000-3-12 standard uses the same measurement topology as the one previously given in EN IEC 61000-3-2 Figure A.2.
The LMG Test suite carries out the compliance tests according to the requirements for direct measurement in §7.2.
The standard foresees also a method based on calculation by validated simulation for determination of conformity, which may be used in case the requirements of direct measurement are not met. This alternative method lies partly outside the scope of the LMG600 and the LMG Test Suite software. The power analyzer and software can be used to determine the validation reference as described in §7.3.a, to which the following simulations will be compared.
The LMG600 in cooperation with the LMG Test Suite, measures the harmonic currents as explained in §4.2.2 of the standard. This involves determining the smoothed 1.5s RMS for individual time windows, as defined in EN IEC 61000-4-7, as well as calculating the arithmetic average of the DFT time window values over the entirety of the observation period.
The test report shall contain all information relevant to the determination of the reference current, the used short circuit ratio, the minimum required short circuit ration and the applied table, as well as test conditions and observation times.
Scope of the EN IEC 61000-3-3 and EN IEC 61000-3-11 standards is the limitation of voltage fluctuations and flicker disturbances inducted into the public low voltage power grid. Such voltage fluctuations are a result of current changes on the network impedance, coming from the equipment under test (EUT).
This standard applies to EUT with input current no greater than 16 A per phase. The EUT is meant to be connected to low-voltage public power grids with line-to-neutral voltage between 220 and 250 V and frequency of 50 Hz.
The voltage source G must fulfil the requirements of §6.2, while the measuring equipment must carry out the measurement according to the EN IEC 61000-4-15 standard. The network impedance is (0.24 + j0.15) Ω on the phase conductors and (0.16 + j0.1) Ω on the neutral.
For single phase measurements the same circuit applies if the 2 of 3 phases are ignored. In the software, operation of 1 or 3 phase EUT is clearly selectable.
The user shall make sure that before each test the general conditions of §6.6 as well as the EUT-type conditions of Annex A are applied. The LMG Test Suite allows for the selection of the type of the EUT as described in Annex A and applies the according test conditions and limits during each test.
The EN IEC 61000-3-3 standard describes also further methods for flicker evaluation besides the flicker meter, such as simulation or analytical approach. These alternative methods are out of the scope of the LMG600 and the LMG Test Suite. In any case, for flicker evaluation, measurement is always the reference method.
The EN IEC 61000-3-11 applies to electrical and electronic equipment with rated current up to 75A, meant to be connected to low-voltage public power grids with line-to-neutral voltage between 220 and 250 V and frequency of 50 Hz.
The EUT in this standard is subject to conditional connection, meaning that the EUT is not necessarily evaluated using the reference impedance as defined in the EN IEC 61000-3-3. This also covers devices with rated current up to 16 A that fail to meet the limits when tested according to the EN IEC 61000-3-3. In such cases these devices may be retested according to the EN IEC 61000-3-11 standard.
The test setup is given by Figure B.1 of the standard and is generally identical to the one described in above in EN IEC 61000-3-3 with the only difference that the value of the network impedance depends on the test and measurement procedures explained in §6.
For EUT with rated current up to 16 A the same test conditions specified in Annex A of EN IEC 61000-3-3 are to be applied. To equipment rated above 16 A apply the general test conditions of §6.6 of EN IEC 61000-3-3. Furthermore, different conditions and limits apply to EUT that is switched manually. The correct application of the test conditions depends on the user, who shall also give them as inputs to the test setup in the LMG Test Suite. Depending on the above, the software will carry out the corresponding procedure to determine conformity.
The network impedance is a key parameter to the test. The decision between using the reference impedance Zref or the selection of a test impedance Ztest lies on the user. Depending on the user selection of network impedance, the LMG Test Suite will either use the directly measured flicker properties, or adapt them according to §6.2.3 to the Ztest If the calculated values meet the limits of §5, then compliance with that standard may be declared.
In case the aforementioned limits are still not met, the procedure of §6.3 is carried out, using the maximum permissible system impedance Zsyst to evaluate the flicker properties as described in §6.3.2.
Environmental concerns that were considerably amplified the past 20 years have made clear that it is of major importance to reduce any energy waste. An undeniable source of that waste is the variety of modern electronic devices that consume energy while being connected to the mains but not operating under their primary function. Typical examples include LED indicators of a device’s off state, digital clocks on ovens and microwaves, or internal electronic circuits being on a standby state for remote switch-on commands or sensor inputs.
The present day, the number of electronic devices that implement such low-power functions is estimated to billions, leading to an estimation of the yearly energy consumed in the range of tens of TWh.
These limits are therefore design specifications for electrical and electronic products meant to comply with the EU regulations. As a result, the development phase of any new product requires reliable measurement of its power consumption in low ranges. The International Electrotechnical Commission specifies the methods of low power measurement in the IEC 62301 standard. The European EN 50564 published by Cenelec, derives from IEC 62301 but extends its scope to cover a wider range of household and office equipment. The EN 50564 is the only one applied for CE marking. Given the above, in the following paragraphs emphasis will be given to the EN 50564 standard.
The ZES ZIMMER solution, uses the LMG600 for the accurate power measurement in combination with the LMG Test Suite for carrying out the tests according to the standards, applying the limits and reporting the results.
Measurement of low power is not a simple matter. A detailed analysis of the challenges in low power measurement can be found in our Application Note 112: Measurement of standby power and energy efficiency.
Even for high end power analyzers it is often a challenge to detect and measure correctly the fast pulses/spikes that appear in low power modes. Moreover, such sudden current jumps make it hard for a user to select the appropriate current range. The influence of low power factors makes the situation even more complicated. The cause of low power factors in low power states is not only the non-sinusoidal currents that are commonly present in these modes, but also the use of EMC-capacitors that can lead to significant phase angles between current and voltage. The problem is more or less the same: low power must be measured using a much higher current scale. The low active power that is of interest is actually transferred through a current much higher than necessary, resulting from the high apparent power that is present.
It is therefore important that an instrument that measures low power must provide current ranges with high crest factors. This way, the uncertainty error can remain relatively small when a small current scale is used instead of a higher one, while the current spikes do not lead the instrument in an out-of-range state. Naturally, auto range selection is in this case out of the question, as it can lead to inacceptable measurement gaps. Further appearance of gaps in the measurement can be blamed to limited data processing and transfer capabilities of the instrument as well as to DC-offset compensation errors. In this case, high processing power and high quality components is what makes a high-accuracy instrument.
Last but not least, no voltage or current meter is perfect. In other words, every volt-meter has a very high but finite internal resistance which leads to a current leak through it, and every amp-meter has very small but non-zero internal resistance that leads to a voltage drop over it. Any possible power measurement wiring will carry one of these two imperfections to the result. But for measurement of low current, a wiring is preferred where the amp-meter is connected to the load-side of the circuit. This way the power meter measures the actual current in the load and the inevitable measurement error comes from the voltage drop on the amp-meter. This error is normally very small compared to the actual voltage of the load. However, one cannot risk a current error when measuring low current. Therefore a wiring with the volt-meter on the load-side is not recommended, as the small current leak though a voltage meter would be comparable to the small current through the load.
There are differences in the definitions of accuracy between the EN 50564 standard and the EU 1275/2008 Commission regulation. The first only specifies the accuracy of the measurement instrument while the latter, the accuracy of the entire measurement setup. This very fact requires special attention, as the EU regulation rules, override the EN 50564 standard.
Real time analysis of the measured values: true RMS, peak, crest factor, etc.
The methods of power measurement described in EN 50564 standard apply to electrical equipment operating in a low power mode. Rated output voltages may vary within 100-250 V AC for 1-phase devices or 130-480 V AC for other devices.
Off mode: The product does not provide any function other than the indication that the product is in the off state.
Standby mode: The product provides one or more user oriented or protective functions such as activation of other modes, status information or sensor based functions.
Network mode: At least one network function is activated such a reactivation over a network command or network integrity communication.
There are several product types that may incorporate and one or more of low power functions into one or more main functions under different switching conditions between one another. These types are defined in detail in §A.5 of the standard.
A low power mode test involves several procedures that need to be carefully taken care of the user, such as preparation of the product, proper warm-up and achievement of a stable state, as well as recognizing and separating different low power states.
Furthermore, low power loads can be distinguished according to their stability to non-cyclic or cyclic, meaning that a product in a low power mode can either have a stable power consumption behavior or follow a regular sequence of power states over time. Different procedures apply for each case.
Sampling method: The recommended method for all types of modes and necessary when the stability of the mode is under question. Involves the recording of power samples over equal time intervals and their evaluation according to §5.3.2.
Averaging method: Is only permitted for non-cyclic loads. Includes the averaging of the power over an observation time by two ways: either by direct measurement of average power or calculation by measuring the energy and dividing it by the monitoring period, as described in §5.3.3.
Direct meter reading method: May only be used when the power consumption of the product is proven to be stable over a sufficient observation period. The exact procedure is described in §5.3.4 of the standard.
Deciding which stability mode applies and which method should be used depends eventually on the user. The user must additionally control that the test procedure is carried out properly when it comes to wiring, energizing the product before the test and taking care of any further details that require human input. The LMG Test Suite provides all measurement methods for any stability mode that can be selected in the pre-test settings. The software evaluates the readings as each method requires and concludes to the final pass/fail results.

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