Toroidal Transformers

[studentspark]

Any issues using these for ELV LED MR16 lamps, if minimum load is achieved

What are the possible issues of running a few lamps off the one tranny. The load is so low from the lamps, that I think I will have to put a few on to get up to load.
Distance about 12 m

 

[333rocky333]

Do torroidals have a minimum load

 

[studentspark]

The one Im looking at is 20-50VA

 

[333rocky333]

The one Im looking at is 20-50VA

really , what make is it
Issues you may have though are with overvoltage to the lamps

 

[studentspark]

http://www.neweysonline.co.uk/newle...n;jsessionid=4EFAB170CC0E1A35BF5C9ECB3D1341E9

 

[333rocky333]

Yeah your right, it may be to do with the short and overload protection within the unit.
The toroidals i encounter are usually just fused wire wound transformers and as far as i recall the input is just proportional to the output

 

[ericmark]

Some thing seems wrong. It states no electronics yet it says it regulates?

In my loft I have a unit looking the same which powers 4 extra low voltage lamps but there is no regulation it delivers a % of incoming voltage.

The NLLV200 and NLLV1X200 seem to have same spec other than terminal type and min output so one wonders if there is an error in the advert?

It does not give the weight I would call in and ask to see one and see how much it weighs then you will know if high or low frequency unit.

Nearly all power supplies for ELV lamps use toroidal transformers but some use electronics as well to both regulate and change the frequency so the transformer can be smaller.

The main advantage of LED and Cold Cathode lamps as well as low current is the ability to handle larger voltage fluctuations. Most LED's are around 1.2 volt so clearly there must be something inside the lamp to reduce the voltage further. What seems unclear is if this will work with DC, low frequency and high frequency alike. Some do claim a voltage tolerance of 10 - 30 volt.

My transformer which looks the same as one shown is 50Hz output and there is no electronics within it.

 

[RF Lighting]

A proper torroidal transformer does not have a minimum load requirement, so will be ideal for LEDs

One thing to check is that the LEDs will run on AC, as most of the dedicated LED drivers output DC. You could always knock up a rectifier though.

 

[ricicle]

And don't connect the cpc to the centre bolt

 

[bernardgreen]

And don't connect the cpc to the centre bolt

Well you can at one end of the bolt but not at both ends. For those un-aware if there is any connection from one end of the bolt to the other end that passes round the transformer then a shorted one turn secondary is created and very high currents will flow in it. At best the fuse on the primary will blow but often the transformer primary overheats and is damaged.

Toroids without a load will have an output voltage that is a constant percentage of the input voltage. When loaded the output voltage will drop. The amount of drop depends primarily on the resistance ( NOT impedance ) of the secondary winding and the amount of current drawn. The resistance of the primary has a minor effect on voltage drop as does the size of the transformer's core.

 

[davelx]

Some thing seems wrong. It states no electronics yet it says it regulates?

"offering excellent voltage regulation"

regulation in this context is a characteristic of all transformers and is to do with how the output voltage varies with load:

http://www.zen22142.zen.co.uk/Design/dcpsu.htm

which is what BG is referring to above.

 

[Space cat]

The amount of drop depends primarily on the resistance ( NOT impedance ) of the secondary winding and the amount of current drawn. The resistance of the primary has a minor effect on voltage drop as does the size of the transformer's core.

In a well designed transformer, I would expect the copper losses in primary and secondary to be roughly equal. Each winding should drop the same fraction of its working voltage under load. Core size is determined by volts per turn (which is the same for both windings) and the core material itself. There must be enough core in there to avoid saturation.

 

[ericmark]

reg·u·late
   [reg-yuh-leyt]
verb (used with object), -lat·ed, -lat·ing.
1. to control or direct by a rule, principle, method, etc.: to regulate household expenses.
2. to adjust to some standard or requirement, as amount, degree, etc.: to regulate the temperature.
3. to adjust so as to ensure accuracy of operation: to regulate a watch.
4. to put in good order: to regulate the digestion.

I can't see how one can consider a simple transformer as regulating the output. With the quartz tungsten lamp the envelope temperature is very important and in the main the whole idea of reducing the voltage is to also introduce some regulations so the envelope is at the correct temperature.

OK in with the case in question that's not an issue but if I was selling a power supply I would not want to call it regulated unless it was. One would expect either a manual or automatic method of adjustment.

There would seem to be something wrong with the description. Either it's a plain transformer with no regulation in which case great for job in hand or it's not a plain transformer and the electronics are using the mark/space ratio of a inverter so has both a min and max output. In which case could be a problem for job in hand.

I would expect it's a plain transformer but since it states min and max output I would say ringing up and asking would be most sensible approach. May be better as an email then you have a record.

 

[Space cat]

In the days before cheap semiconductor devices, one way to get a reasonably constant voltage from a variable source and with variable loads was to use a constant voltage transformer. We actually had these things in three of our accelerators before they went to the scrapyard.

They were curious looking devices with odd shaped cores which were very big for their power rating. They relied on core saturation to limit the output voltage and they incorporated a tuned circuit to cut down on harmonics. They were clever stuff in their time. I've never heard of this design being built in toroidal form and I'm not even sure if it's possible but who knows what's inside the OP's encapsulated transformer.

PS: One of those old accelerators even used a magnetic amplifier to control its focus coil current. Happy days. I'm beginning to think I should post this in here:

http://www.diynot.com/forums/electrics/good-old-days.317622/