Buzzing

T666,
I've had the same issues with my recent cbus installation. We found that the electronic transformer was the source of buzzing. We tried 3 different brands (ie. Nelson,Atco,Osram ) but could not find one that reduced the buzzing sound completely. The best one that came close was Luxman ETH70. The different between this one and the others that we tried, is that it has a capacitance on 0nF in the specifications.
I am still trying to source one that has no buzzing at all. One that is Leading edge Only and has low Capacitance.
If their is anyone that can help, please reply.

 

Hi Speakerroom,

Both the Luxman ETH70 and the ETH105 have 100nF capacitance on their inputs, NOT 0nF.

The lowest capacitance/per watt transformer on the Clipsal recommended list is the Eurolite WT-105L, which is a 105 watt tranny.

I havent found any that have zero capacitance.

Have a quick look at the attachment:

Hope this helps, Darpa

 

Darpa,
My information has come from Compact Lamps Australia the sole distributors of Luxman. They informed me that the Latest ETH 70 has a Capacitance on 0nF.

 

Fair enough Speakerroom, I stand corrected

 

Hi Speakerroom. I am not disputing there claims, however it is my understanding that the capacitance is required for EMC Compliance (C-Tick). It's strange how all the "well known" manufacturers need a capacitor to comply ???

Also, I was informed by Osram that there are potential instability issues when the capacitance is lowered. They claim they (internally) tested Speedy, Possum and other "low-capacitance" transformers and found that they suffered from fluctuations in light level setting (wavering) at low levels. This was the reason they chose to use a 130nF input capacitance for the new Osram Redback.

I am unsure if ANY of this is true, but it's be interesting to actually measure one of those Luxman transformers - if they have found the solution that everyone else can't, then that is great !

Cheers, John

 

100% correct John.

The problem appears to only be with the PRO range of dimmers when the total capacitance (per channel) is below 500 - 600nF.

 

Capactiance loading

gday guys,
Ive had a little bit to do with capacitance loading and the problems it can cause.From that i have been told from adelaide that the Max cap loading of proseries dimmers is 1000nf a channel and the DIN mount Dimmers are 300 nf per channel.If you do a serach on transformers or capacitance theres plenty of reading

 

Nick,

The maximum capacitance is not the issue, it's the minimum capacitance levels that are causing the problems.

 

wow, another issue..minimium capacitance...so there is only a narrow range (500 - 100nf), is that correct?

By the way, I have also heard from a Luxman saleman from China that the ETH105 has no input capacitance (but the ETH70 has)...........

also in a recent case, the buzzing is from the "light" litself. The client is using a remote magnetic transformer which connected to a number of spotlights. When dimmed, the lights are buzzing but the transformer is at the other side of the room. I wonder if it is the light or the old dimmer (the old 750W 4 channel dimmer).

 

Just another thing on this subject, the Clipsal electronic transformer compatability chart lists transformers that meet the input capacitance requirements of C-bus dimmers or at least recomends the maximum number of any one type of dimmer that can be connected to any one channel of a particular C-bus dimmer and still meet the capacitance requirements as of the date of testing. Clipsal do not have any control over the build quality of other manufacturers products - a product may be ok today but one made next week may not be built to the same quality, loose windings on inductors etc - not saying this is the case with these transformers but in general as a guide it is best to qheck that the transformers manufactures haven't changed the input capacitance and that the product has been put together correctly.

And another nother thing, In my experience the electronic transformers with 0 nF input capacitance were the most expensive as they had been designed to solve the problem that the input capacitace cures (radiated EMF from the switch mode power supply inside) buy more eligant (and expensive) design methods and circuitry, waking a relativly big cap across the input is a cost effective way of achieving EMC standards.

On a lighter note it may well be that the days of the electronic transformer and Fluro ballast are numbered as some bright spark has worked out that the cost of manufacture and (even more so) the cost of disposing of the units when it ultimatly dies exceeds the cost of power saved by their relative efficiency.

 

Question:

If CIS are creating 'maximum' total capacitance recommendation lists / charts, have you tested for minimum (total) capacitance on Pro Range dimmers?

 

Absolutely correct - however the MEPs for fluorescent ballasts has already been introduced, and MEPs for ELV Transformers is coming upon us really fast. For fluoros, the old wire-wound Low Loss (B1) and Semi-Low-Loss (B2) are still allowed, and no plans to ban them. However, the cost of copper is on the rise and the electronics prices are falling - it now costs about AUS$8 for an OEM to buy a brand-name 1x36W electronic ballast, and maybe $1 more for a 2x36w. Even cheaper if you want to take a risk on a chinese manufactuered ballast. That makes electronic 2x36W cheaper to install than 2x36W wirewounds, a capacitor and 2 starters.

But for the ELV Transformers, if I remember correctly they are stating a max 10W loss on a 50W trannie, which will effectively wipe out the old Atco black TM50 wire-wounds. So, all we will be left with is crappy, asian-made electronics with dubious build quality... unfortunately we Aussies (as a rule) only want to buy the cheapest, irrespective of how bad it is ! We consumers have a lot to do with the situation we are now in, and it'll only get worse.

Anyway, the whole thing will be resolved when the new Cbus dimmers (eventually) arrive... the whole concept of using Leading Edge dimmers on Electronic Transformers is a disaster waiting to happen. Use a proper trailing edge dimmer and none of these problems will occur.

John

 

I think you will find the Less Capacitance the Better. The pro series dimmers do not have a need for a minimum Capacitance.

 

I was poking around on another ummmm... manufacturer's site and found an interesting Transformer Compatability chart.

In that chart they don't make a comment about the Atco Speedy, but they DO make a very blatent comment about noise from Osram HTM 70 and 105 'Mouse' transformers !

So, seems that there is more to this whole subject than meets the eye (or ear?) !

Link to : Opposition Company to CIS

 

Hi thanks for all the discussion on this topic. Its been a while since i posted. My CBUS system has been working great no problems at all, i didnt take more pictures yet until its fininshed becasue im still just on the top level this is a very slow renovation My transformers still buzz but i have found the only time i can hear it is if im reading a book and i never read, so with a computer / tv on the buzz canot be heard I still think that some scientist should invent a way of dimming a light without noise resulting. Is the transformer squealing because it has to eat some of the power instead of sending all of it to the light? well why cant the transformer just route that power back into the board instead having to deal with it?. note: i am not a scientist dd

 

Sorry in advance for the long post...

They already have - there are a VAST number of very effective ways of dimming halogen and incandescent lights. The problem is that Leading Edge wave-chopping dimming is the cheapest way, and everybody (in the private sector) always wants the cheapest product.

The noise problem lies with the "way" that wave-chopping dimmers work - without explaining it too scientifically, imagine a nice smooth wave in the surf. Not a breaking wave, just a wave-shaped lump of water moving into shore. That is what "normal power" is like... and when that water strikes a pylon or wall it doesn't make much noise because the change in water level is "smooth"... slowly moving upwards, and then downwards again.

The total amount of "power" is determined by the total amount of water inside that that wave form in the surf. If you wanted less "power" (less water movement) then the logical way would be to reduce the size (height) of the waves, but retain them the same shape. This would result in less power - the problem is that this way of dimming electricity is very expensive.

One method of controlling the water would be to chop off the beginning of the (ocean) wave.... so the height of the wave was the same, but instead of a smooth "ramp" of water at the front there is a vertical wall of water moving into shore. When that wall of water hits something there is a huge "crash" of energy, creating a loud noise. That's exactly what Leading Edge Dimmers do with electricity waves, it's the sudden increase in power at the beginning of the wave that makes the noise.

Trailing Edge dimmers are similar, except that they chop off the rear of the wave instead. This creates a smooth front of the waveform, but a sudden drop-off at the back - this will not create as much noise either with water or with electricity waves, since the noise is only caused by a sudden increase in water / power, and not caused by a sudden decrease (that make sense?).

Open this page from Vossloh website : http://www.vossloh-schwabe.de/eng/technische_hinweise/gluehlampen/141.php The shaded areas in the diagrams represent the part of the waveform that has been removed (dimmed), and you will be able to see the sudden "chop-off" of the waveforms when these methods are used for dimming.

OK, to summarise - Leading Edge dimming is the cheapest method, but it's also the most likely to create noise. It is NOT a good thing when the load is capacitive, since the capacitor presents a virtual "short circuit" to that instant increase of power when the waveform is dimmed (chopped). That short circuit tends to cause the dimmer to be overloaded, hence the de-rating and maximum capacitance requirements of leading edge dimmers. Even when used with other load types, the Leading Edge dimmer tends to create magnetic fields that cause buzzing - so you get what you pay for.

Trailing Edge is the correct method of dimming capacitive loads like electronic transformers - and will always be MUCH quieter. You cannot use Trailing Edge dimmers with Inductive loads like motors and wire-would transformers, but they work perfectly well on resistive loads like incandescent lamps. Trailing edge dimming costs a bit more than leading edge, due to more complex electronics.

The new C-Bus Universal dimmer switches between Leading and Trailing Edge, after it detects what kind of load is connected. This is a good way of handling things if you want a conventional (cheapish) approach.

Dimmers that reduce the "overall size" of the waveform (retaining a pure sine wave) are very rare and only used in specific commercial and industrial applications. No domestic project would be prepared to pay for these methods, nor accept the power losses (inefficiency) and size of these kinds of dimmers.

There is a method termed "IGBT" (Insulated Gate Bi-Polar Transistor) dimming. This is virtually noiseless, and is widely used in the entertainment industry where low-noise and interference is more important that cost. There is very few domestic transformers available for this method (some extremely high-end decorative products like Flos contain IGBT-dimmable transformers).

Probably the best way is to distribute the dimming - so rather than have a high-powered dimmer on the mains, to instead have a dimmer in each transformer! This is the way that fluorescent ballasts are dimmed now-days... there is no dimmer required for these devices - you send them a digital signal to set light output at 50% and they just "do that". That is probably the best way to dim halogens, but of course it costs more than a AUS$6 chinese electronic transformer

For example, Tridonic make a variety of electronic transformers for DSI and DALI control... here's a link to just one model :

http://www.tridonicatco.com/kms/cms/kms.php?id=86&str_id=541&det_back=1

Hope that helps explain it, at least a little bit