Austin Transformers

[RadioFan2J3]

Anyone have any experience with the full load to no load variation on the output of an Austin transformer wired for 230VAC on the output side?

I've got a location where the techs claim the output voltage is up to 275VAC on the output side, and is said to be burning out the tower lights rather fast. To clarify, they've not put in any new bulbs since the last failure and this is the reading without any load.

I've asked them to try to check the voltage unloaded and loaded down, perhaps with a pair of beacon bulbs, to verify there is a regulation problem.

We relamped the towers where this problem is occurring some time back and two of the towers have no problems, only the third tower has this problem.

I don't have ready access to the location, and trying to work on this somewhat remotely.

I realize this isn't a lot of information, but all that I have at the moment.

 

[frankberry]

That's a lot of sag. Do the other transformers show the same amound of sag when under load?
With that much sag, I'd almost think that the transformers are too small for the load.
That being said, it may not be a problem at all. As soon as the current begins to flow through the lamps, the voltage will sag. The cold resistance of the lamp filaments is quite a bit lower than the hot resistance. You'll get maximum sag as the lamps are just beginning to draw current.
In the past, I've adjusted the transformer taps so as to reduce the secondary voltage slightly to extend the life of the lamps..

 

[RadioFan2J3]

That's a lot of sag. Do the other transformers show the same amound of sag when under load?
With that much sag, I'd almost think that the transformers are too small for the load.
That being said, it may not be a problem at all. As soon as the current begins to flow through the lamps, the voltage will sag. The cold resistance of the lamp filaments is quite a bit lower than the hot resistance. You'll get maximum sag as the lamps are just beginning to draw current.
In the past, I've adjusted the transformer taps so as to reduce the secondary voltage slightly to extend the life of the lamps..

Thanks for the reply. I am not sure if the transformers are too small, as they have been installed for something like 20 years or so. I don't normallly have access to the location and I am working with the folks somewhat remotely.

Let me look further into your suggestions.

 

[boiseengineer]

So the lights are on both sides of the seconday 230V center tap for 115V to the lamps?
Something weird going on with the neutral? Is one of the legs shorted to the tower.

 

[RadioFan2J3]

So the lights are on both sides of the seconday 230V center tap for 115V to the lamps?
Something weird going on with the neutral? Is one of the legs shorted to the tower.

I will need to clarify, the primary voltage is a nominal 240VAC. This is in a location where 240VAC is the usual voltage - not a US location.

Tower has one set of flashing beacons and one level of side lights, all bulbs are 240VAC.

Don't think anything is shorted to the tower. RF is not a factor, for reasons beyond this discussion.

I am trying to rule out an issue with the Austin transformer for the moment.

I saw two of the techs yesterday and tried to determine if that voltage reading was an unloaded voltage on the output side of the Austin transformer and would it drop to a more usual 240VAC with some load. I don't have an answer yet.

Normally, anything which changes the voltage ratio of a transformer, turns ratio, would be a defect within the transformer, shorted turns particularly, and there would be other issues, mostly overcurrent and tripping breakers, especially if there are shorted turns on the primary side.

I've not had Austin transformers in my operations, and looking to see if anyone else has ever had anything like this to happen.

 

[TomT]

Single phase should be 240, three phase 208. Of course, it's rarely that...we see considerable variation on our 3 phase feed. Third world power company out here in WV.

 

[secondchoice]

Single phase should be 240, three phase 208. Of course, it's rarely that...we see considerable variation on our 3 phase feed. Third world power company out here in WV.

You must be talking about the Snowshoe area.

 

[RadioFan2J3]

Single phase should be 240, three phase 208. Of course, it's rarely that...we see considerable variation on our 3 phase feed. Third world power company out here in WV.

Our nominal mains are 240VAC phase to neutral, 415AC phases to phase.

I was considering buying stock in a light bulb company the three weeks or so the phases voltages were running upwards of 257VAC phase to neutral.

 

[BobOnTheJob]

If the voltage is going that high when unloaded, you can be sure of this : When the first lamp fails, the second lamp will fail much quicker as the voltage will be somewhere between the loaded and unloaded values. In the USA, we often purchase 700W 130V bulbs rather than 620W 120V bulbs. The higher voltage rating of the bulb offsets the higher wattage rating and the light output is similar...the primary reason for doing this is longer bulb life. Is it possible to buy a higher voltage/higher current bulb in that country?

 

[RadioFan2J3]

If the voltage is going that high when unloaded, you can be sure of this : When the first lamp fails, the second lamp will fail much quicker as the voltage will be somewhere between the loaded and unloaded values. In the USA, we often purchase 700W 130V bulbs rather than 620W 120V bulbs. The higher voltage rating of the bulb offsets the higher wattage rating and the light output is similar...the primary reason for doing this is longer bulb life. Is it possible to buy a higher voltage/higher current bulb in that country?

Re the bulbs, the owner takes care of buying the bulbs. I just get my tower guy to climb.

We had changed out the bulbs on all three towers in the spring and they should have lasted longer. I am told two of the towers have no problems, just the one.

And yea, I've done the same on bulbs higher voltage and wattage - bulbs are normally cheaper than climbers.

We will try to get access to the site and play around with loading down the Austin to see if it really is very poor voltage regulation or there is another issue. It isn't at my work site and I have to work through others for the initial indications. I am thinking that the transformer may be one of the dual winding models, a winding opened and in fixing the problem, using some taps they have screwed up the secondary voltage.

 

[RadioFan2J3]

OK, so for the update on this.

The high voltage on the secondary side of the Austin transformer was a combination of wrong taps on the transformer, actually setting up the secondary side to be a higher voltage than the primary side.

The primary voltage was also quite high, running upwards of 250VAC, and that has been corrected by the power company.

We put new bulbs in all the tower lights and hopefully they will last a lot longer.

 

[Tom Wells]

Ummm, how bright were the lights when it was in stepped up config?

I mean, did it just look regular?

 

[RadioFan2J3]

Ummm, how bright were the lights when it was in stepped up config?

I mean, did it just look regular?

Tom, don't know.

I never saw the tower lit at night. We had changed the bulbs out maybe a year back, and all we could tell what that the bulbs were working, when changed. Daylight hours, of course.

Only the center tower had the Austin transformer, the other two towers are grounded and powered directly off the power line. The line voltage must not have been too high, as the grounded tower with a beacon, the two beacon bulbs were OK.

The site wasn't mine and I got involved only because we have a tower climber and he doesn't mind the trip out in the country.