X-Ray transformer questions / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

X-Ray transformer questions

Move Thread

LAN_403

sparky99

Fri Dec 07 2007, 02:54AM

Registered Member #1159 Joined: Fri Dec 07 2007, 02:10AM
Location: Hudson Valley of NY State
Posts: 84

Hello all,
New to the forum, but have been a high voltage junkie since I was a kid. I recently acquired an X-ray transformer from a friend who owns a X-Ray supply company. I was looking for a 100KV xfmr from a dental unit, but couldn't turn down the 125 KV 300 ma transformer & control unit he gave me. The transformer is a Universal Model 3550.
So far, I've got the transformer up out of the oil with a come-along & have it supported over the tank with 2x4's. Its filament transformers have ben removed, along with the 4 diode strips that formed the bridge rectifier. The xfmr has 2 secondary coils with a common primary. The high side of each coil has 2 leeds, one on each side of the coil, The inner side of each secondary coil is brought up shrink wrapped with each primary leed. one goes to ground & the other to the controller metering circuits. I know these have to be tied together & am pretty sure they should be grounded, correct? If they were just tied together, they would certainly have to ber rerouted, far away from the primary leeds. Here's a picture of the schematic, but I don't see any continiuty from the inner leg of the left side secondary to the transformer core.
Next, some controller questions. The unit is designed to work on 240 VAC. Will I get full output from the transformer with 240 Volts input? The reason I ask is because the controllers autotransformer has taps that go from 48 volts to 300 volts.
I was thinking about using the autotransformer as a ballast for current limiting, so I don't smoke my watt-hour meter & explode the 5KVA pole pig that feeds my house.
Last, The transformer oil. The manufacture date on the transformer is 1989. I believe the first restriction on the use of PCB's was in 1974 & then totally banned in 1979. So, am I safe to assume that this oil is non PCB?

Thanks for reading this! Your thoughts & ideas most welcome.

Sparky99

MOT_man

Fri Dec 07 2007, 04:51AM

Registered Member #1127 Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139

Yep. I'd say that it is 99% PCB free. XRAY trannies are usually submerged in slightly off yellow Napha based insulation oil. PCBs are very sweet smelling chemical and the vapors irritate the eyes - nearly clear and produces a green flame when flame is past over it.

J. Aaron Holmes

Fri Dec 07 2007, 05:46AM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Have to agree with MOT man on the PCB risk. There may be trivial amounts of PCB in there just because so much PCB-contaminated equipment remained in use at transformer factories long after the bans were put in place, but anything made in the 80's would have been subject to the < 50ppm definition of "PCB-free", as far as I know. My first big oil-filled trannies were some Westinghouse pole pigs from the 1960's. I bought some test kits and checked them out. "No" (< 50ppm) PCBs. Which was nice. I've heard that PCBs were actually more common in stuff like capacitors than in transformers, but I don't know if that's correct. If you watch eBay for big caps, though, you'll frequently see people selling caps full of PCBs (people see names on the caps like "Pyranol" and "Askarel" and don't realize that these are just brand names for PCBs).

Always wanted to play with an X-ray transformer. Unfortunately, my transformer collection draws frustrated glances and head shakes from my wife almost daily

...so I probably won't be adding to it for at least another year (This year's Transformer Season has already come and gone).

You only have a 5kVA transformer feeding your house? Wow. Turn on any two 240V appliances in your house and you're probably pulling double what that poor runt is rated for

(EDIT: In the U.S., that is, where "240V" means water heaters, furnaces, and electric ranges) Around here, the rule of thumb for transformer ratings seems to be 12.5kVA per house or 15kVA, whichever is larger. I share a 50kVA unit with three neighbors. Curiously: What's your breaker panel or fuse box rated at for amperage? The only 5kVA piglets I see in these parts are used to power traffic signals.

Cheers,
Aaron, N7OE

Steve Conner

Fri Dec 07 2007, 10:58AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

5kVA pigs are common out in the country here.

Yes, you do have to ground those two leads.

A ghetto way to test for PCBs is to try lighting a small sample of the oil on fire. If it burns cheerily, it's just ordinary oil. If it glows green and you die of cancer, it's PCB.

sparky99

Tue Dec 11 2007, 11:57PM

Registered Member #1159 Joined: Fri Dec 07 2007, 02:10AM
Location: Hudson Valley of NY State
Posts: 84

Thanks for the response. I did the quick & dirty tests on the oil: It floats on water & no green flame when exposed to fire. After reading all the stuff on PCB's on the Tesla webring, I decided to go for a test kit. Cheap enough for some peace of mind.
My place upstate has a 5KVA pole pig. Down here, there's a 25KVA pig feeding 7 houses. I guess NYSEG like to run things right at the edge.
Stay tuned, several mor questions coming later tonight

Bob

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob