Harmonics & Flicker

 Standards:    

IEC/EN61000-3-2    
Limits for harmonic current emissions (Equipment input current <16 per phase).

IEC/EN61000-3-3
Limitation of voltage fluctuations and flicker. (Equipment input current <16A per phase)

These standards became a mandatory requirement on Jan 1st 2001. THere have been several amendments since then, the latest version is IEC61000-3-2 (2006) which included some significant changes to the measurement requirements.

 
 The Harmonic standard deals with the limitation of harmonic currents injected into the public mains supply system. It is applicable to electrical and electronic equipment having an input current up to and including 16A per phase and intended to be connected to public low-voltage distribution systems (ie supply voltages nominally 230V ac or 415V ac 3 phase.
The scope includes products such as lighting equipment, portable tools, all electronic equipment, consumer products and appliances and industrial equipment.
This standard does not cover equipment which has a nominal supply voltage less than 220V ac and no limits have been specified for professional equipment above 1kW.

Note however that there is a similar US document IEEE-std-519:1992 although no tests are currently mandated in the US, and the Japanese are proposing a variation for use in Japan. 

The Flicker standard covers 2 aspects:
- Estimation of the ability of a product to induce flicker in lighting that is connected to the same electrical supply. This is only likely if the product draws heavy current in pulses at a repetition rate between 2Hz and 25Hz. If this characteristic is not likely, then the product can be declared compliant without testing.
- Inrush current. This is required for all products.

 

  Whilst the EUT is operating under normal conditions, the harmonic content of the current drawn by the EUT is measured. There are currently four sets of limits that are applied corresponding to the ‘class’ of the equipment. Classes are A, B, C or D depending on the type of EUT.

Class A:  Balanced three phase equipment and all other equipment, except that stated in one of the following classes.
Class B: Portable tools.
Class C: Lighting equipment, including dimming devices.
Class D: ITE Equipment.

The ‘Waveshape’ criteria which was specified in earlier editions of this standard no longer applies.

For each class, a set of harmonic limits are specified.
Class A and B limit values are specified as absolute levels and include all harmonics up to the 40th.
Class C limits are specified as a percentage of the fundamental current and are applied to the odd harmonics only (up to 39th).
Class D limits are specified in terms of rated load condition (W) with an additional absolute maximum. Again these are applied to the odd harmonics only (up to 39th).

The new (2006) version of the standard introduces new requirements for the measurement of interharmonics and revised analysis processing.

Whilst testing the product, the input mains supply should itself be free of mains harmonics. Limits are specified for the value of allowable harmonic content in the supply. Typical mains supplies will exceed these limits thus the use of a special power source to deliver harmonic free mains is normally required.
The standard specifies in detail how the harmonics are measured, with particular attention given to fluctuating harmonics and test conditions.
 

 

 The Laplace range includes all that is required for full compliance testing of products. It includes a harmonics and flicker analyser, PC software and a 1kW clean power source. The AC2000A harmonics analyser can be used up to 16A per phase, but for products with a rating >1kW, mains supply must be provided either by a high power clean power source or the public mains supply. The analyser includes a function that will measure the mains supply harmonics so that the siutability of the mains can be checked.

Use of the harmonics analyser without the clean source is entirely acceptable, and the compliance measurements will be valid provided that the results show the results are significantly below the limits.

  

AC2000A Mains harmonics analyser. Fully complies with IEC61000-3-2 (2006).
This analyser is shipped complete with PC software, RS232 and USB interfaces, plus Flicker analysis feature. Apart from having a very powerful harmonics measurement and flicker analysis capability, the analyser is also a fully featured power analyser which displays VA, W, power factor, crest factor, phase angles, THD, peak voltage and current and harmonic current measurements.

AC1000  1kW power source. Provides a ‘harmonic free’ mains supply to comply with IEC61000-3-2 requirements.  The typical mains supply in the UK will have a THD of between 2% and 5%. The standard requires an THD of 0.1% or better. The AC1000 provides this 'clean' supply by using active waveshape control to 'clean' the incoming mains.

  Help in the selection of the appropriate measurement techniques and automatic display of the relevant limit levels are standard features in the software provided with all Laplace EMC analysers. Note The above is for guidance only. Refer to the published standard for definitive details, exclusions and exceptions and detailed test technique.