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News Release from: Laplace Instruments | Subject: C2000 Harmonics and Flicker analyser
Edited by the Engineeringtalk Editorial Team on 30 March 2000

Full compliance measurement to
IEC61000-3-2 and 3-

The AC2000 Harmonic and Flicker analyser from Laplace enables simple and automated testing to the mains harmonics and flicker standards.

As from 1 Jan 2001, EMC conformity will include the requirement to comply with limits on mains harmonics and flicker imposed on the mains by the product Many modern electronic and electrical products draw current from the mains in a very non-linear manner, inevitably creating harmonic signals

These distort the mains voltage and create problems for the supply and distribution networks.

Given that the numbers of electronic devices connected to the mains seems set to ever increase, control of the harmonic emissions is an obvious requirement.

The AC2000 Harmonic and Flicker analyser from Laplace enables simple and automated testing to the standards.

The unit will test all products up to the 16A maximum power rating required by the standard, and display all harmonics in real-time against the limit values.

These results can be shown as a histogram, or in a chart recorder form, together with a simple pass/fail indication.

For loads up to 1kW, the optional AC1000 low cost power source can be provided.

This supplies a clean (harmonic free) mains supply to fully meet the requirements of IEC61000-3-2, and permits fully compliant testing, even if the mains supply exceeds the harmonic criteria.

The AC2000 also measures Flicker in accordance with IEC61000-3-3.

This is a requirement for products that impose fluctuating loads on the mains supply.

It is a measure of the ability of the product to cause lighting to flicker at frequencies which cause human discomfort.

The analyser indicates instantaneous flicker perception, short term value (Pst) and long term value (Plt).

Fully compliant with the standard, the AC2000 enables the user to self test and self declare in total confidence.

All test parameters and setup information are controlled by the user via an exceptionally simple, prompt driven soft key system on an LCD display screen The AC2000 costs under £1000 and the AC1000 is under £500.

The IEC61000-3-2 Harmonics Standard deals with the limitation of harmonic currents injected into the public mains supply.

It is a mandatory part of the EMC regulations as from 1/1/2001 It specifies limits for current up to and including the 40th harmonic of the mains supply and it is applicable to all electrical and electronic equipment having a rated input current less than 16 amps and using a nominal supply voltage of 230V.

In other words, it applies to virtually everything that plugs into a normal 13A mains socket.

There are 4 classes: Class A: Basically everything not covered by the following classes.

Class B: Portable tools Class C: Lighting equipment, including dimmers.

Class D: Equipment having an input current with a 'special wave shape' and an active power <600W.

The 'special wave shape' basically defines a current with a significant peak each half cycle.

This is a common feature found in many power supplies, particularly the classic rectifier/reservoir capacitor type.

The standard specifies many criteria for measurement techniques, selection of the class and calculation of limits, some of which are defined as a percentage of the fundamental current drawn and others as absolute levels.

Other criteria include an allowance for harmonics that exceed the limit, but only for less than 10% of the total time in a 2.5 minute observation period.

Clearly, assessment of compliance is not straightforward! IEC61000-3-3 The Flicker Standard: Flicker is a measure of the fluctuation of lighting caused by mains voltage variations.

This standard sets limits on the amount of voltage variation a product can impose on the mains supply.

Products that tend to cause these variations are those which vary their supply current from the mains in a pulsating manner.

Physiological visual perception is maximised at approximately 8Hz and so Flicker measurements are frequency weighted with a maximum sensitivity at this frequency.

It is this frequency that can provoke epileptic fits, so flicker is not a trivial problem! Tests are not required on equipment that is unlikely to produce significant voltage fluctuations in this frequency range.

The evaluation of Flicker involves the measurement of load current over a specified time period and performing a statistical analysis on the results.

Two parameters are calculated, short term flicker severity (Pst) and long term flicker severity (Plt).

Pst is normally calculated over a 10 minute period and Plt is normally 12 times the Pst period.

The standard specifies that the maximum allowable value of each flicker severity parameter is 1.0.

During a routine test, the analyser would automatically time the duration of the measurement, indicate the current flicker perception value and process the data to obtain the Pst and Plt values at the end of the test.

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