Electronics > Beginners
Is my 15KV neon light transformer broken ?
<< < (3/4) > >>
beanflying:
Yep external Scrape and paint. Most of them are Bituminous filled or similar. I have already stripped and cleaned the terminals and insulators as much as possible as mine was well used.

A few basic cautions 15kV will travel over moist surfaces! Assume everything around the transformer can conduct when you are first testing it.

Play Safe  ;)
BravoV:

--- Quote from: rsjsouza on March 20, 2019, 05:12:12 pm ---Obviously that you can simply try to test with a regular DMM's ohmmeter (which only puts out DC) and see if you have any of such effects in your measurement.
--- End quote ---

Update, tested using Fluke 189, manual range at Mega Ohm range, it started to flicker from infinite resistance to about > 200 Mega Ohm and slowly , I mean like at few seconds starting to crawl upward like 230 .. 240 ... 250 and so on.
BravoV:

--- Quote from: beanflying on March 21, 2019, 08:14:45 am ---A few basic cautions 15kV will travel over moist surfaces! Assume everything around the transformer can conduct when you are first testing it.

Play Safe  ;)

--- End quote ---

Thanks for the reminder, yeah, I will be very cautious and triple check at every connection made, and probably quadruple checks all over again before I power this thing. Also it will be put above a stool in the middle of the room, instead on top of bench table.

Waiting for my order to arrive of few meters of HV motor spark plug wire at local motorcycle repair/modding shop.
Psi:
if you're worried the primary might short you could put a resistive load in series with NST primary for the first power up.
A high wattage mains voltage incandescent lamp is a good load for this, if you still have one around somewhere.
If anything shorts out the lamp will just light up and nothing will go bang.

Note that you will have to remove this lamp before trying to get arcs from the secondary. The 15kV 30mA will be too much to draw through a normal 100/200W lamp. So the lamp will lightup if you try get any arcs.

The usual failure mode for a NST is one of the two output sides going short.
So you get an arc from one side to case but not the other side to case.
Zero999:

--- Quote from: BravoV on March 20, 2019, 03:26:37 pm ---
--- Quote from: Fraser on March 20, 2019, 01:36:06 pm ---This thread may be of interest. You can calculate the inductive reactance of the primary.

https://www.physicsforums.com/threads/mains-transformer-with-1-4-ohm-primary-winding.924900/
--- End quote ---

Thanks for the link.

So, my primary reactance based on my measurements above ...

Reactance :
= 2 x pi x freq x inductance
= 2 x 3.14159 x 50 Hz x 0.414 Henry
= 130.06 \$\Omega\$

So at 220 VAC the primary current will be -> 220V / 130.06 \$\Omega\$ = 1.69A ?

Much lower than the rated current (2.25A) as printed at the label isn't it ? :-//
--- End quote ---
The primary's inductance should be much higher than that. The magnetising current will be tiny, compared to when it's loaded.

The problems is the inductance of the transformer will be frequency dependant and meters often test at a much higher frequency, than the mains.

I think the transformer is most likely fine. As mentioned above, connect it to a spark gap, turn on the power and keep well back. Note that 15kV at 30mA, is a high enough voltage and current to be lethal!
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod