2002

RF emissions from energy-efficient fluorescent lighting

Conventional tungsten filament lamps are entirely without radio frequency emissions, except in rare fault conditions. However, because they are inefficient, the UK government is promoting use of energy efficient alternatives in support of its climate change policy. These include energy efficient fluorescent lamps, which produce high levels of RF interference.

For a fluorescent tube to operate at high frequency an electronic switching ballast is required. A typical operating frequency for an electronic ballast would be in the region of 20kHz to 40kHz. The high frequency ballast is essentially a switching power supply and has the potential for radiofrequency interference in the same way as any switched mode power supply. Dimming is achieved by reducing the power applied to the fluorescent tube. In order to maintain the discharge, the frequency of operation must increase as the light output level is decreased. Thus a typical electronic ballast which operates at around 30kHz for maximum light output will supply the lamp at increasing frequencies up to approximately 100kHz for minimum light output.

Measurements of sample lamps have shown that electronic ballasts can cause an increase in interference in long wave and medium wave bands to portable radio receivers. The minimum distance of a radio receiver to the lighting samples for good reception varied between samples. Of particular interest was the interference to AM services from the dimming ballast. Because the fundamental ballast operating frequency alters as the lamp is dimmed, so interference to individual radio stations depends upon the light output level of the unit. For example at maximum dimming (minimum light output) the second harmonic of the lamp operating frequency fell at the same frequency as BBC Radio 4 Long Wave (198kHz) and so reception of this station at maximum dimming was considerably worse than the reception for other long wave stations.

Moreover, VHF band 2 FM radio reception can be affected by electronic ballasted fluorescent lamps with batten type fittings. Modern lighting technologies and techniques do give rise to significant emissions in the VHF band. In practice these emissions are seen to be limited to an upper frequency of less than 300MHz at present, but since the EMC standard for lighting (CISPR 15) gives no tests above 30MHz, these emissions are effectively uncontrolled by any legislation.

2004

Harmonics from low-voltage lighting can cause overheating

In the lighting industry, simple switch-mode power supplies with AC outputs, often called "electronic transformers", are used increasingly to operate 12 volt lamps from the mains supply. In a retail store 50-100 of these units each rated around 50W would not be uncommon.

Most of these devices claim to meet the EMC Directive individually and are CE marked. However if a number of these devices are operating in one location, then their total emissions can be shown to exceed the limits for both RF and harmonics, sometimes by a large margin.

There are already instances of other equipment malfunctioning, and of sine wave distortion causing conventional transformers to overheat (due to enhanced core losses). A building had recently been fitted with about 50 off 50W "electronic transformers", the harmonic emissions from which so distorted the mains supply waveform that conventional transformers powered from the same mains distribution overheated.

Clearly, this is not just an EMC issue, but a significant safety concern. But experience so far is that lighting equipment manufacturers, on the whole, don't seem to understand this significance of this problem, and that installers could not care less.

Interference from lighting is an ever-increasing threat

(IEEE 2005 EMC Symposium)

Standard CISPR15 (EN 55015) is a special product family standard for electrical lighting and similar equipment that has served the market well for many years, but in recent times the incidence of interference from lighting has increased. This has coincided with technological developments in the lighting industry. With the increasing pressure for more energy efficient lighting and because of requirements for more energy labelling of household lamps, there will be an increase in the use of technologically advanced lighting. This is the reason, why CISPR15 has been seen to be insufficient and it is under revision.

Unlike the generic standards and most other product family standards, CISPR15:2000 contains no requirements for radiated emissions from 30MHz to 1GHz. Also in Finland, it has been found that some lighting appliances are causing harmful interference to radio communications on the VHF band. Therefore these lamps and luminaires are not in compliance with the EMC Directive (EMCD), although they might fulfil the requirements of CISPR15.

Energy saving lamps (ESLs) are typical sources of interference to TV VHF broadcast receivers and also to private radiotelephone networks on the VHF band. Finnish EMC market surveillance authorities, the Safety Technology Authority (TUKES) and the Finish Communications Regulatory Authority (FICORA) have received several interference complaints concerning ESL bulbs.

In 2003, FICORA solved ten interference cases caused by ESLs. In a new conference hall in Tampere, Finland, these kinds of lamps were installed throughout the building. Radiated interference from these lamps was so high that it was not possible to use VHF radiotelephones inside. All ESLs were then replaced. The bandwidth of the interference was about 50MHz (-30 dBc points) and the interference occurred on the frequency band 159 - 209MHz. In Finland, this band is used by many different radio services including emergency services (police, fire brigade, ambulance services, etc.).

TUKES has also received other complaints concerning interference cases caused by ESLs. Typical equipment being disturbed has been, for example, the remote control of TVs or narrow band in-house telecommunication networks using domestic 50Hz/230V electricity mains wiring. The disturbances between TVs and their remote control equipment was mostly caused on the infrared band, for which there are no requirements at all. In local telecommunication cases, conducted EMI from ESLs made it unable to use domestic electricity wiring as media for signal transmission. Also, other fluorescent lamps have caused both kinds of disturbance.

Finnish market surveillance test results with regard to ESLs have been a little better than those from Germany. According to Finnish tests, 43% of ESLs do not fulfil the standard. In Germany, 48% has failed. In ten cases, emissions from ESLs were so high that TUKES was obliged to restrict the distribution of the lamps (sales bans). Surprisingly, defects were found to be equally distributed between inexpensive and expensive ESL models.

Also in the USA, surprisingly high conducted emissions from some ESLs have been measured in the band 450kHz to 2MHz. The need for measuring was prompted by problems with AM radio reception while ESLs were in operation, and levels approaching 100dBmV occurred at the low end of the MF band. At 1.7MHz, the levels were more reasonable, but were still in the region of 70dBmV. The majority were reported as very high-order harmonics of the supply frequency, which suggest that the rectifier should have had shunt capacitors and/or soft recovery diodes. If these emission levels are common, where does that leave the troublesome subject of power line communication? It seems to both provide a case for relaxed limits and an indication that communication may be compromised by the very emissions that support that case!

The most troublesome interference case in Finland concerning metal halide lamps (MHLs), occurred in relation to a public swimming pool. The rated life time of the type of MHLs used was 10,000 hours usage, but after 2,000 hours, the sparking interferences of the lamp's electrodes during normal operation caused serious interference to TV receivers in a neighbouring house. When the lamps were exchanged for new ones, the event repeated itself after about 2,000 hours.One regrettable detail was that the pool had to be once again emptied before it was possible to change the lamps.

In Finland, there has been one very serious interference case caused by a single rechargeable torch model. After about half a year's use the regulatory circuit together with the battery began to oscillate causing serious interference to one TV channel. Before identification of this problem source, many interference cases were noted all around Finland. In fact, this could be considered to be more of a battery-charger problem than a lighting interference one.

Market surveillance on ESLs

(Joint Cross-Border EMC Market Surveillance Campaign Carried Out in 2004/05 By European Market Surveillance Authorities, EMC-ADCO 20(06)04, 2006)

A Joint Cross-Border EMC Market Surveillance Campaign was conducted between 1 October 2004 and 31 May 2005. The campaign was actively supported by 16 market surveillance authorities participating in the EMC Working Group on Administrative Co-operation.

The purpose of the campaign was to check the technical compliance of Energy Saving lamps (ESLs) products with the radio-frequency emission requirements of the EMC Directive. The principal conclusions drawn from the campaign were as follows:

Although there does not appear to be an intrinsic problem with the Energy Saving Lamps (ESLs) as a whole, because of very poor results from ESLs originating from some manufacturers an overall 23% of all the samples tested failed to meet the disturbance voltage (conducted emissions) limits of the relevant European harmonised standard EN55015. ...

Although not part of the original campaign, some samples were also tested for harmonics emissions in accordance with EN61000-3-2. Of the 142 samples tested, 23% failed to meet the requirements of the standard.

Market surveillance on LED lamps

(FINAL REPORT ON THE 4TH JOINT CROSS-BORDER EMC MARKET SURVEILLANCE CAMPAIGN (2011) LED LIGHTING PRODUCTS)

As a result of discussions at the 29th EMC Administrative Cooperation Working Group (EMC ADCO) held on the 5th and 6th of October 2010 in Budapest, and following an impact assessment procedure it was agreed that the fourth joint cross-border EMC market surveillance campaign should assess the compliance of LED lighting products.

The results of the technical compliance with the applicable harmonised standards showed large differences:

Rather low compliance with the emissions limits: 61.5% of the tested, one hundred and sixty-six (166) products were found to be compliant

There was a better level of compliance with the immunity limits: 91.5% of the tested, forty-six (46) products were found to be compliant.

Within this market surveillance campaign an additional study on harmonic current emissions (EN61000-3-2) was carried out. When applying the same harmonic limits as those for compact fluorescent lamps, one out of two samples, 46% of the assessed LED lighting equipment failed. This is clear evidence for the need of a prompt amendment of EN61000-3-2.