"Robert L. Berger" wrote: >> Load must be varied to maintain the proper output voltage of the >> transformer, or >> early failure will likely result. >> >> I would like to see the source of this data!! >> > Check out the sites of the companies that make the transformers. That is where I got the information from, but unfortunatly I lost all my bookmarks to a virus. I will see if I can find them again.
>> > > While I have never designed a transformer of neon sign service, I > have designed transformers for the old tube type ham radio > transmitters, as well as pulse welding transformers, and your > statements do not compute. Why. If a transformer is designed for a specific voltage, and the voltage is 50 to 100% more, then the likelyhood of insulation breakdown increases dramatically. If it is designed for 20 mA, but you are running 30 at a lower voltage, the dissipation is 2.25 times as much, and it will overheat. I know for a fact the latter can happen, as I burned one up early on in only a couple of days until I started monitoring my current and voltage and keeping them within the recommended range. Neon sign transformers are impedence limited as far as current is concerned. They have to be, since a neon lamp exhibits a negative resistance region, and you need a ballast type action. They need a high open circuit voltage to strike, and operate at a much lower voltage once lit. They do this with a magnetic shunt. If you look at the transformers I am using at http://www.transco-neon.com/tfoot.htm you will see that the unit is rated 15KV open circuit and 30 Ma short circuit. But the power consumed under normal operating conditions is 243 watts. That is because it is speced to operate at about 9-10 Kv and 20 to 25 mA, which if you multiply out and add power lost in the transformer, will add up to about 250 watts. If you call the company and request the data sheets on the unit, they will send them to you, and should show a VI curve which indicates an impedence limited source. I have these graphs around here somewhere from a couple of neon sign transformer companies. Marshall OK, found a couple of references, from one company. Other companies say the same essential thing. The curves on the transformer I have indicate proper operation is at about 70% of nameplate voltage, but the following reference says 50% for theirs. To be safe get the operating specifications on you specific transformer: http://www.franceformer.com/faqdetail.asp?FAQDataDis_Action=Find('FAQNumber','53')&FAQDataDis_Position=FIL%3AFAQType+%3D+%27Neon+Transformers%27ORD%3AABS%3A2KEY%3A53PAR%3A http://www.franceformer.com/faqdetail.asp?FAQDataDis_Action=Find('FAQNumber','65')&FAQDataDis_Position=FIL%3AFAQType+%3D+%27Neon+Transformers%27ORD%3AABS%3A14KEY%3A65PAR%3A: Question: 3.014 What is overloading and what affect does it have on a transformers life? Answer: Overloading, or the connecting of more tubing than recommended, produces higher secondary voltages resulting in increased stress on the transformer and sign insulation system. This stress can cause secondary coil failure and reduced transformer life and premature failure of high voltage sign components. Overloading can also ... creating high voltage and current peaks in the secondary coils, damaging the insulation system in the transformer and sign, and again, significantly reducing transformer life. http://www.franceformer.com/faqdetail.asp?FAQDataDis_Action=Find('FAQNumber','66')&FAQDataDis_Position=FIL%3AFAQType+%3D+%27Neon+Transformers%27ORD%3AABS%3A15KEY%3A66PAR%3A: Question: 3.015 What is underloading and what effect does it have on a transformers life? Answer: Underloading, or connecting less tubing than recommended, forces the transformer to supply more tube current than normal, resulting in increased wire loss and higher operating temperatures in the transformer. This reduces the life of the transformer.
