I have bought some very nice Military surplus transformers (steel potted, apparently very high quality) .
primary 115V/0.7A and sek. 6.3V/12A (and with shield)
I intended to connect two primary windings in series for 230V line voltage application.
So far so good.
But one thing I have overlooked - they`re rated for 400Hz line frequency (as most of the Military power stuff)
Is there any way to use them on 50Hz line frequency though?
I believe it should be possible but very likely don`t get the rated power out of them.
Do You think I can use them on 50Hz at all?
If yes, what do You think which amount of decrease in output power I have to expect - 20%- 30% - or even more?
Thank You for any kind of input!
primary 115V/0.7A and sek. 6.3V/12A (and with shield)
I intended to connect two primary windings in series for 230V line voltage application.
So far so good.
But one thing I have overlooked - they`re rated for 400Hz line frequency (as most of the Military power stuff)
Is there any way to use them on 50Hz line frequency though?
I believe it should be possible but very likely don`t get the rated power out of them.
Do You think I can use them on 50Hz at all?
If yes, what do You think which amount of decrease in output power I have to expect - 20%- 30% - or even more?
Thank You for any kind of input!
or seriously overheat.Probably the core will go into saturation because of the increased number of volt-seconds, causing excessive currents and blown fuses or overheating.
At 50Hz, a transformer with one primary winding intended for 115V, 400Hz should be able to handle 115V*50Hz/400Hz=14.375V without saturation. With two windings in series, you can go up to 28.75V. Not very useful with 230V mains.
At 50Hz, a transformer with one primary winding intended for 115V, 400Hz should be able to handle 115V*50Hz/400Hz=14.375V without saturation. With two windings in series, you can go up to 28.75V. Not very useful with 230V mains.
Forget is completely!
Only if you lower your mains 8 times also
400Hz is/was common on aeroplanes to save weight and these trannies probably come from that area. But these are completely unsuitable for 50/60 Hz, period. Be careful with 50 Hz, they will for sure go into saturation and because these are hermetically canned, will for sure explode with a big bang when given sufficient time, and that can be lethal!
Cheers
it`s a pity
that`s what I thought too.
But it has still inductance also at a lower level.
So when I load them with a (much) lower current than rated I thought it should be possible.
I wanted to hook up the two primaries in series not secondary windings - so with series connected primaries and 230V I should get about the same secondary voltage as rated for 115V (6,3VAC - for tube filaments).
Moreover saturation is current/power dependend and I don`t think voltage ratings alone tell anything about saturation.
Pjotr,
after Your responds it seems to be clear that I can`t use them for what I have them intended but I would be satiesfied with a much lower secondary current rating in order I can use them at all for something else.
Do You think it`safe enough when I power one up very slowly with a variac and load it increasingly with an adjustable power resistor while monitoring the temperature of the transformer?
For additional safety precaution I could test them outside under some sort of enclosure.
Me thinks the temperature should be a good indicator if the transformer is overloaded - isn`t it?
If this would be reasonable, what do You think how far up I can go in temperature?
Anyway, many thanks for Your help !!!
dhaen,
that`s what I thought too.
But it has still inductance also at a lower level.
So when I load them with a (much) lower current than rated I thought it should be possible.
MarcelvdG,
I wanted to hook up the two primaries in series not secondary windings - so with series connected primaries and 230V I should get about the same secondary voltage as rated for 115V (6,3VAC - for tube filaments).
Moreover saturation is current/power dependend and I don`t think voltage ratings alone tell anything about saturation.
Pjotr,
after Your responds it seems to be clear that I can`t use them for what I have them intended
but I would be satiesfied with a much lower secondary current rating in order I can use them at all for something else.Do You think it`safe enough when I power one up very slowly with a variac and load it increasingly with an adjustable power resistor while monitoring the temperature of the transformer?
For additional safety precaution I could test them outside under some sort of enclosure.
Me thinks the temperature should be a good indicator if the transformer is overloaded - isn`t it?
If this would be reasonable, what do You think how far up I can go in temperature?
Anyway, many thanks for Your help !!!
Dear Cocolino,
I'm also talking about primary voltages. A transformer with two 115V, 400Hz primaries connected in series should be able to handle 28.75V of primary voltage at 50Hz (giving the same primary current as 230V, 400Hz). Of course the secondary voltage will then become about 6.3V*50Hz/400Hz=0.7875V.
I'm also talking about primary voltages. A transformer with two 115V, 400Hz primaries connected in series should be able to handle 28.75V of primary voltage at 50Hz (giving the same primary current as 230V, 400Hz). Of course the secondary voltage will then become about 6.3V*50Hz/400Hz=0.7875V.
cocolino,
unfortunately you cannot use the 400Hz transformers @50/60Hz without lowering the primary voltage, because the core saturates.
With Uind = -dPhi/dt = -L*dB/dt
you can see, when you increasing dt by 8 (one eigth of the frequency) you must decrease Uind (=primary voltage) by 8. Because of economical reasons the core is driven near by the saturation Bmax.
unfortunately you cannot use the 400Hz transformers @50/60Hz without lowering the primary voltage, because the core saturates.
With Uind = -dPhi/dt = -L*dB/dt
you can see, when you increasing dt by 8 (one eigth of the frequency) you must decrease Uind (=primary voltage) by 8. Because of economical reasons the core is driven near by the saturation Bmax.
cocolino said:Well, it looks like that I can actually forget them completely.
Anyone needs some nice and cheap transformers?
Thanks to everybody for the lesson!!
Those might be actually pretty good if used with AC power regeneration circuits, just like ML does. But the secondary is a bit low for any practical SS applications (maybe only in 5v digital circuits?).
You might use step up transformer (as suggested by Fred http://www.diyaudio.com/forums/showthread.php?s=&threadid=3674&highlight= ) but then again you are dealing with 400Hz.
Hmmm...right, good idea... and if I use another (I have enough of them
) of those transformers backwards it would be possible. Like this:
6.3V (adjustable within reasonable limits regarding the transformers ratings) 400Hz power-amplifier output > 6.3V (as primary) > 115V secondary > 115V primary > 6.3V secondary output
For practical implementation of an AC power regeneration circuit it seems to me wether to use 400Hz or any other frequency (as long the transformers can take it, as I have learned today) should not matter much.
Remains the question if the (pretended) advantage would be beneficial enough to justify the huge efforts to power a digital circuit this way?
Peter or anyone, do You know if this is already used in commercial digital equipment (I know that Madrigal uses this principle to power the input stages of some of their SS-power amps, but digital....)?
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