I've seen it mentioned here and there on the net, that people use, let's say;
2x transformers with 0-9VAC 1,5A secondaries...they then hook those up back to back with the 0-9VAC secondaries in the middle. The point being getting 0-230VAC(230Vac being mains voltage here) from the primaries of the transformer not connected to mains voltage.
Could one use different voltage secondaries to "bump" the 230Vac to...say 260Vac at the output of the second transformer?
Is this a reasonably safe practice?
2x transformers with 0-9VAC 1,5A secondaries...they then hook those up back to back with the 0-9VAC secondaries in the middle. The point being getting 0-230VAC(230Vac being mains voltage here) from the primaries of the transformer not connected to mains voltage.
Could one use different voltage secondaries to "bump" the 230Vac to...say 260Vac at the output of the second transformer?
Is this a reasonably safe practice?
Ahh you mean 245V -> 9V -> 245V?
I’d probably red flag that given the primaries are wound differently - on the second transformer you’re treating the secondary as a primary.
Would it work - yes. Would I want an amp using it? Nope. (I don’t have winding experience)
I’d probably red flag that given the primaries are wound differently - on the second transformer you’re treating the secondary as a primary.
Would it work - yes. Would I want an amp using it? Nope. (I don’t have winding experience)
I have successfully used that kind of setup, but going a bit below 230V.
Say a 230V/18V into the "secondary" of a 230V/19V, to end up at ~218V.
Both transformers are oversized with regard to the required load, and it has been working without adverse effects.
They are both E-I structure, but with different arrangements of primary/secondary (like layered vs separated etc.)
Not being knowledgeable enough, I never dared trying the "step up".
If you try it, keep a close watch to humming or heating or sagging voltages...
260V is like +13% to 230V, maybe a high quality component would survive?
BUT IF IN DOUBT, DO NOT RISK !
_
Say a 230V/18V into the "secondary" of a 230V/19V, to end up at ~218V.
Both transformers are oversized with regard to the required load, and it has been working without adverse effects.
They are both E-I structure, but with different arrangements of primary/secondary (like layered vs separated etc.)
Not being knowledgeable enough, I never dared trying the "step up".
If you try it, keep a close watch to humming or heating or sagging voltages...
260V is like +13% to 230V, maybe a high quality component would survive?
BUT IF IN DOUBT, DO NOT RISK !
_
It may work, but the transformers may get hot. Why? When the 9v secondary of the 2nd transformer is used as a primary, it is the winding that magnetizes the core. Depending on transformer mutual inductance as seen by that winding, excess current flow may occur in order to magnetize the core.
This will always work to ultimately provide a voltage lower than the specified primary voltage at the "secondary" but in the case you describe which attempts to achieve a 260V output from a 230V winding the results may be far from ideal. This is because most power transformers are designed to operate just below saturation so just as placing 260V on a 230V primary could cause issues with heating and excessive magnetizing current, expecting 260V from a 230V winding would do the same.
Could it work??? Yes. Are the chances of it repeatably working well high??? Probably not. A safe rule of thumb is to never expect or apply a voltage higher than the published numbers on a transformer.
dave
Could it work??? Yes. Are the chances of it repeatably working well high??? Probably not. A safe rule of thumb is to never expect or apply a voltage higher than the published numbers on a transformer.
dave
Under ideal conditions, using two transformers back to back will give about 80-90% of the output of a single transformer of the same size, taking twice the space with twice the weight, and having half the regulation (twice the voltage drop under load). If the transformers are free, and power requirements low, it might be worth trying. One handy application is to obtain 50-60VAC for bias by operating a tiny 12V transformer in reverse from a 6.3V winding.
As Dave mentioned, don't try a "step up" as transformers have no more core and winding than necessary to stay out of saturation. Those of us in 60 Hz land can get away with a 20% step-up IF the transformer is rated for 50/60 Hz.
As Dave mentioned, don't try a "step up" as transformers have no more core and winding than necessary to stay out of saturation. Those of us in 60 Hz land can get away with a 20% step-up IF the transformer is rated for 50/60 Hz.
I see.
Thank you all for your help.
I can get my hands on EI-core transformers with single or dual secondaries (the dual secondaries are center-tap).
I had hoped that maybe a couple of Ei-core transformers with 1.5A on the 0-9Vac side would be 1, more cost effective and 2, maybe step up the voltage a bit (that now seems foolish just to save a small amount of money).
Just to see if it is cost-effective, what kind of mA would I see in the output of the example above using two 9vac/1.5A back to back?
Thank you all for your help.
I can get my hands on EI-core transformers with single or dual secondaries (the dual secondaries are center-tap).
I had hoped that maybe a couple of Ei-core transformers with 1.5A on the 0-9Vac side would be 1, more cost effective and 2, maybe step up the voltage a bit (that now seems foolish just to save a small amount of money).
Just to see if it is cost-effective, what kind of mA would I see in the output of the example above using two 9vac/1.5A back to back?
From what I've read here, there seem to be little that speaks in favor of using transfomers back to back. Even considering price. I think I'll steer clear of it.
It is sorta desperate way to get high voltage on a budget in the world dominated by the low-voltage solid-state electronics. There is a point in using two transformers with 6 or 12 volt secondary to get also the heater power, but if you intend to use separate transformer for this, than the isolation transformer (230V to 230V) might be more useful and economical.
if i were to do this, the traffo connected to the mains will have 70va and the step up will be lower, say 50va.
another way is if you have your mains traffo with several taps, like 4.5, 6, 9, 12 vac, then i will connect the other traffo with the 9vac to the 4.5v tap of the mains traffo...
reason is you will still be connecting filaments to the mains trafffo..
another way is if you have your mains traffo with several taps, like 4.5, 6, 9, 12 vac, then i will connect the other traffo with the 9vac to the 4.5v tap of the mains traffo...
reason is you will still be connecting filaments to the mains trafffo..
Hello people. 🖖 I'm wondering if traffo from microwave is rewinded completely (prim. and sec.) is it possible to make normal traffo which can be used for amplifiers ?
I know with rewinding only sec. traffo from microwave is built like that to heat up no matter is it something connected or not on sec., so if I rewind prim. and sec. would that heating be than normal like other traffo which is not from microwave.
I know with rewinding only sec. traffo from microwave is built like that to heat up no matter is it something connected or not on sec., so if I rewind prim. and sec. would that heating be than normal like other traffo which is not from microwave.
Rewinding MOTs is a pain in the *** because the E’s and I‘s are usually welded together. Which means running the entire length of the wire through the core over and over and over again, potentially scraping the enamel off the wire each time thru. I’ve done low voltage secondaries like that but good luck with a primary. It’s just too many turns.
So basically you are asking whether a microwave transformer core can be used for a power transformer for continuous duty.
I guess it is, but probably only for low continuous power.
Getting a real continuous power core is probably cheaper/easier.
Jan
I guess it is, but probably only for low continuous power.
Getting a real continuous power core is probably cheaper/easier.
Jan
Hello Brko, if you mean to rewind both sections I think you would use it in a reverse way (prim->sec and sec->prim).
I wound many transformers but never microwave ones 1-2kV. Also, mind that one wire of the HV is connected to the transformer core so if you use plain the HV as primary beware that you have a live contact on power up.
I wound many transformers but never microwave ones 1-2kV. Also, mind that one wire of the HV is connected to the transformer core so if you use plain the HV as primary beware that you have a live contact on power up.