Millitary Transformer

[Rippey574]

I have this power supply my grandfather started and I have finished it. I am trying to figure the rating for transformer, they are military. I understand easily the wiring and markings... except for the way the have listed the max W.V. and secondary amperage. See the pic...
If you notice the MAX W.V. is at the center, so does it represent the max W.V. for the primary or secondary? If its secondary is that for 6.3-6.3 or the 12.6?

Also the the secondary winding shows the amperage under the center tap, so is this a 20 amp if i use the 12.6 or is it 10 amp,.,. Or could it be used as a 2 10 amps at 6.3?

Other information, they are sealed (presumed) oil filled.
Primary is set up to 115 with both primary's using 110 (1&4 Hot 2&3 Neutral)
Well back to fixing the regulator and drying the stain.

 

[Nigel Goodwin]

The transformer is 6.3V CT - so it can't give 12.6V, it's 3.15V-0-3.15V.

6.3V at 10A is 63W, so it's a 63W transformer.

I imagine it's an antique valve heater transformer?, the tap been for earthing to help reduce hum.

 

[Rippey574]

I just checked the ac values for secondary, 3.539VAC for CT and 7.05VAC for full. They are bridged to get 21.17VAC all to gather. Glad you pointed that out, now I know why my cooling system wasn't going to its full potential. As for their original use, I don't know. He got them when he was in the service (with many other parts) they told him not to ask because they wont tell. That was in the 50's to late 60's if I remember right.

 

[Nigel Goodwin]

I just checked the ac values for secondary, 3.539VAC for CT and 7.05VAC for full. They are bridged to get 21.17VAC all to gather. Glad you pointed that out, now I know why my cooling system wasn't going to its full potential. As for their original use, I don't know. He got them when he was in the service (with many other parts) they told him not to ask because they wont tell. That was in the 50's to late 60's if I remember right.

6.3V is the standard heater voltage - it's even got it's own prefix (E) in pro-electron coding.

 

[Rippey574]

I didn't find an "E" in the numbers, but the amperage would be suitable for a heater element. You also seem to know you stuff, what do you think this would of been apart of? A ship ballast valve or some kind of building valve. I don't see it being used in aircraft since it has a max altitude rating.

 

[Nigel Goodwin]

I didn't find an "E" in the numbers, but the amperage would be suitable for a heater element. You also seem to know you stuff, what do you think this would of been apart of? A ship ballast valve or some kind of building valve. I don't see it being used in aircraft since it has a max altitude rating.

Valve is the real name for what you call 'tubes' - they commonly have 6.3V heaters. For example an ECC83 is an 6.3V heater (E), double triode (CC), using a B9A base (8) - the 3 distinguishes it from other ECC8x valves.

As I understand it, aircraft didn't use 50/60Hz equipment, it was 400Hz or something?, this made it smaller and lighter.

 

[Rippey574]

Valve is the real name for what you call 'tubes' - they commonly have 6.3V heaters. For example an ECC83 is an 6.3V heater (E), double triode (CC), using a B9A base (8) - the 3 distinguishes it from other ECC8x valves.

As I understand it, aircraft didn't use 50/60Hz equipment, it was 400Hz or something?, this made it smaller and lighter.

Can't believe I didn't catch that , your UK they are valves to you. 400Hz would seem good to reduce weight.
I have another transformer that has a 400V secondary, I have been thinking about turning it into a power supply, got any ideas on when or where I would use 400V D or A.C.? I do self experiments and i'm a ham radio.

 

[Nigel Goodwin]

Again, 400V would be for valves, possibly the HT transformer that goes with the heater transformer?.

Both are perhaps for a decent power transmitter?.

 

[Rippey574]

yes, the 400v was for a power transmitter (11M modulator amplifier), unfortunately when I was repairing it, I dropped a transformer on the valves an smashed them. Wasn't able to get a number off the pieces.

 

[duffy]

Could have been worse - imagine if you had dropped the valve on the transformer!

 

[Rippey574]

ha ha, good representation!

 

[stevez]

Interesting discussion. Keep in mind that the spec for the transformer was based on a fixed set of conditions including input voltage and load on the secondary. Manufacturing tolerances along with slight departures from design conditions might explain why 7 volts when you expect 6.3 volts. If your measurements were no load or open circuit you might try adding some kind of load.

 

[Menticol]

Yes, your grandfather's transformer was onboard a plane. Check the 10.000 ft max label. When height increases, the air becomes thinner, and generators & electrical system starts to arcing, if not properly isolated.

Modern aircraft electrical system:
115 VAC, 400 Hz, motor driven generator(s)
28VDC, batteries
115VAC, 400 Hz, battery powered inverter, for emergency use only

There may be also a small turbine called APU, that generates electrical or phneumatic power to start the engines. Instead of APU, an external power supply may be attached, the ground power unit, to do the same.

If everything goes wrong in flight, a small "windmill" called the RAT (ram air turbine) is deployed to provide electrical power to drive the control surfaces on wings and tail

 

[KMoffett]

When height increases, the air becomes thinner, and generators & electrical system starts to arcing, if not properly isolated.

Seems counter to Paschen’s Law: https://www.duniway.com/images/pdf/pg/Paschen-Curve.pdf Do you have a reference?

I think the altitude limit has more to do with the differential burst pressure of the sealed, oil-filled transformer case at altitude.

Ken

 

[duffy]

??? Looks correct to me - 760 torr is all the way over on the left, pressure reduces, breakdown voltage reduces.

It starts going up again, but that's at like half a torr... not sure if you can actually fly a plane in that.

 

[KMoffett]

Oops! Misread the chart. Still seems counter intuitive. Increase in humidity also increases breakdown voltage. Now throw a bucket of water an high voltage circuit.

Ken

 

[john1]

Well, No-one has mentioned that if it was intended for 400 c/s, its not going to give its rated current output at 50 c/s.

 

[Nigel Goodwin]

Well, No-one has mentioned that if it was intended for 400 c/s, its not going to give its rated current output at 50 c/s.

Well the heater transformer, which this thread is originally about, is clearly labelled 50/60Hz on it's photo, and also 10,000 feet - check the first post.

 

[john1]

Yes.
Sorry, I missed that.
It is marked as 50-60 c/s.

John

 

[Hero999]

Another interesting thing is that an increase in humidity actually increases the breakdown voltage which is pretty counter intuitive. It's only when you get condensation does the breakdown voltage decrease.