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 Power transformer
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 Return to top of page · Post #: 1 · Written at 5:35:23 PM on 8 September 2018.
Aurther Dungar's Gravatar
 Location: Brisbane, QLD
 Member since 8 July 2018
 Member #: 2263
 Postcount: 11

Does anybody have information on a power transformer 18 - 4150 (1966)
possibily used by Kriesler
I just want to know how much I can safely pull on the six volt winding.
thank you.

 Return to top of page · Post #: 2 · Written at 4:59:32 PM on 12 September 2018.
Sue's avatar
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

What I would do is load the filament winding with globes until the output drops to 6.3V, then measure the current. If it's any help, I've just measured a Kriesler 18-101 transformer this way, and the output at 6.3V is about 2 amps.

 Return to top of page · Post #: 3 · Written at 4:17:47 AM on 13 September 2018.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 766

QUOTE: load the filament winding with globes until the output drops to 6.3V,

If your mains voltage is higher than back in the day, you'd need to compensate. If you now have 240VAC, but the transformer was designed for 220VAC, I'd stop loading the 6.3V heater winding when you get it down to 6.8V.

 Return to top of page · Post #: 4 · Written at 9:26:22 AM on 13 September 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4339

The thing with a lot of Australian transformers used in Radio, that was not common in USA, is that they had primary tappings which allowed a voltage range from 200 to 260 allowing a safety factor.

With the introduction of "State Grids" anything outside 6% is illegal. I recently had a utility transformer (now replaced) that was leaking oil & it was running around and exceeding 252VAC: 252V being the upper limit.

I have photos of it; it's likely close to 50 years old & the oil based dirt was around half way up the primary's insulators.

If anyone knows what it actually came out of, it would be handy to feed back the info. Wa2ise method will work.

 Return to top of page · Post #: 5 · Written at 7:32:14 PM on 13 September 2018.
Relayautomatic's avatar
 Location: Canberra, ACT
 Member since 24 April 2012
 Member #: 1136
 Postcount: 122

If that transformer was 50 years old then the 'oil' would have been PCB. I hope you you did not get any of it on your skin or on your clothing/work gear. If the 'oil' dripped on the pole or ground then that area would be contaminated. PCB is very nasty stuff in liquid form and even worse when vapourised or burnt..

 Return to top of page · Post #: 6 · Written at 9:34:57 PM on 13 September 2018.
Brad's avatar
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6348

Transformer oil is supposed to be replaced by the supply authority periodically. Some of the larger transformers get done every second year whilst others the timespan is longer. When a transformer is just left to buzz away for half a century, the end result is quite predictable. Unfortunately it is just not economical to transmit at less than 11kV, which is why each customer has their own substation in the bush. The electrical losses are too great at the distances the lines span.

AS 60038 dictates that the nominal low voltage is 230V +10%/-6%. This was more or less equal to the previous voltage, 240V +/-5%. Each state, however, has it's own interpretation of the standard and a couple haven't bothered ratifying it. Additionally, no state has lowered its voltage for practical reasons, given that the old nominal voltage and tolerance is pretty much equal to the new one on paper, which made the whole exercise pointless to begin with, like many things that governments and unelected standards bodies drum up.

Most of the time, if you plug a digital multimeter into a GPO, it'll read somewhere between 242V and 248V.

With most electronic equipment now able to plug into a supply anywhere between 100V and 250V, the actual output voltage is not that important provided it falls somewhere in that range. Anything with an electric motor, though, will require a more stringent approach. There's three things that electric motors do not like: 1. Running with no load, 2. Running whilst stalled, and 3. Being fed with the incorrect voltage.

A valve a day keeps the transistor away...

 Return to top of page · Post #: 7 · Written at 10:02:26 PM on 13 September 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4339

I did have a dig at AusNet about the oil. I worked in chemistry for a large part of my life & that stuff is tame, compared with some we used.

No stress dealing with it. We put the power underground & being so old, I am sure that undoing the taps for the second time in six years, last prior to that, in 1983, was the last straw for the seals. The new one was set 240V at the transformer & its around 50m to the house. Total underground around 600m: Four feeders from a meter box, to four sub boards & one sub board feeds the house sub board.

On the original SWER in 62 before upgrade to single phase off two wires. I did have contactors to stop the motors (including fridge) when there was a phase fail (normally lightning initiated) & the power dropped to around 100V.

 Return to top of page · Post #: 8 · Written at 11:13:15 AM on 14 September 2018.
Sue's avatar
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

OK then. Taking into account the mains voltage in your area, select the appropriate input voltage, 220V or 240V, load the filament winding until you get 6.3V, and measure the current.

 Return to top of page · Post #: 9 · Written at 1:07:02 PM on 14 September 2018.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 881

Brad's comment about motors not liking to run on no load may have puzzled some people but he has a point.
In the olden days a motor with a classic winding would draw magnetising plus efficiency current on no load and that woud be a low value.
Then as the motor is loaded the current rises, the power factor swings more resistive as shaft kW are delivered.

Not necessarly true with motors after about 1990 or so. I first bumped into this oddity when investigating the multiple failure of motors in a grain process shed. The designer had oversized some screw feed motors by heaps and they were burning out in droves. I did a current check and first met motors that drew high current on idle falling to normal on medium load and full load on full load. I simply went and got one motor of 1/4 the hp but that would fit straight in and checked current and temperature as within limits over 4 hours operation. Much to the amazement of the plant electrician.. All motors were swapped out for same make same frame but less guts and no more was heard . I never did any further testing but when I used motors in my own designs made sure the HP rating was what I required, no more no less and I never had any trouble.

Somebody more clued up on motor characteristics may have a better insight on the phenomena.

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