Abstruse "not a transformer" stuff

[plugwash]

The trouble with "electronic transformers" is they have a high frequency AC output. That leads to all sorts of problems when driving anything other than the intended load of a short cable running to an incandescent bulb.

A SMPSU with a DC output should have far less problems with driving long cables.

 

[bernardgreen]

The trouble with "electronic transformers" is they have a high frequency AC output.

This is an old item but the team are still active
http://www.emcia.org/awareness/Pages/InterferenceExamples/HouseholdAppliances.htm

A well-known make of wireless baby alarm is known to cause occasional interference with aircraft communication at some U.K. airports. It is not the wireless technology in the baby alarm that is the problem, it is their plug-top power supply, which uses a switch-mode converter. A faulty batch of power supplies was shipped with the baby alarms, and although they function well enough they emit powerfully on VHF radio channels used by National Air Traffic Services (NATS).

Commentary

This source of interference was found to be due to a spurious oscillation that occurred when the internal cables were in a certain position. Designers should ensure that their products’ performance is not significantly affected by the minor variations that will inevitably occur during production.

Even assuming the product had been tested for radiated emissions, it is possible that the test was performed on a sample that did not exhibit the spurious oscillation, though this does not absolve the manufacturer from responsibility. It is also possible that the plug top power supply was only tested for conducted emissions up to 30MHz, in the mistaken belief that it had no mechanism to generate disturbances above this frequency.

Most plug-top power supplies these days use switch-mode power conversion technology, which involves power devices switching at between 50 and 500KHz. However, because they must switch at very high rates to maximise efficiency and minimise heat losses it is easy for them to emit significant amounts of emissions at up to 1000 times their basic switching rate. So a 100kHz switcher might give high levels of emissions at 100kHz intervals all the way from 100kHz to 100MHz.

Such plug-top power supplies must employ filters and other techniques to prevent their emissions exceeding statutory limits. Sometimes a batch is made with faulty or missing filter components, or with a design change that has not been tested for emissions. If the manufacturer is not employing QA methods that ensure that EMC compliance is maintained in volume manufacture, the ‘noisy’ power supplies can find their way onto the market.

Today there are too many dubious manufacturers who ignore the regulations when designing cheap SMPS modules.

a more recent item
http://www.ukqrm.org.uk/smps.php

DIYers who are using SMPS module to power equipment should be made aware of the hazards associated with the use of SMPS modules which may not be compliant with EMC ( radio frequency interference ) regulations.

 

[ban-all-sheds]

The trouble with "electronic transformers" is they have a high frequency AC output. That leads to all sorts of problems when driving anything other than the intended load of a short cable running to an incandescent bulb.

A SMPSU with a DC output should have far less problems with driving long cables.

And a SMPS with a high frequency AC output would have exactly the same problems as an electronic transformer.

The reason for that is that there is no link between what is written on the outside of the enclosure and what is housed within it.

 

[ban-all-sheds]

This is an old item but the team are still active
http://www.emcia.org/awareness/Pages/InterferenceExamples/HouseholdAppliances.htm

The problems cited in that report were not due to how the power supply was labelled. It could have been labelled "electronic transformer" or "switch mode power supply" or "AC adapter" or "power supply" or "<makers name>" or it could have had no "name" at all, and the internals would still have been the same.

The name is irrelevant to the EMI problems.

Today there are too many dubious manufacturers who ignore the regulations when designing cheap SMPS modules.

I'm sure there are.

And I'm sure that there are dubious manufacturers who ignore the regulations when designing cheap electronic transformers.

The name is irrelevant to the ignoring of the regulations.

a more recent item
http://www.ukqrm.org.uk/smps.php

An article all about interference from Switched Mode Power Supplies.

No mention of "electronic transformers".

Remind me again why naming a SMPS made as an ELV lighting supply an "electronic transformer" is the cause of problems?

DIYers who are using SMPS module to power equipment should be made aware of the hazards associated with the use of SMPS modules which may not be compliant with EMC ( radio frequency interference ) regulations.

Indeed they should.

And they should be made aware of the hazards associated with the use of badly made corn-cob LED lamps.

They should be made aware of the hazards associated with the use of incompetent electricians.

They should be made aware of the hazards associated with the use of Volkswagen diesel cars.

The list is probably indefinitely long.


Or maybe we should focus on properly, and aggressively, with the most hideous penalties for infringement, enforcing the regulations and holding those who sell or import, or facilitate the sale or the import, of contravening items to account.


OOI, why can't DIYers who are using electronic transformers to power equipment be made aware of the hazards associated with the use of electronic transformers which may not be compliant with EMC ( radio frequency interference ) regulations?