You can use a standard dual winding transformer as an autotransformer to step up (Boost) or step down (buck) small voltages. This video shows how that is done.
It's really difficult to find any good articles or videos about kVA calculations for these circuits. I'm in a program now trying to get my head around it -- I know autotransformers and therefore, Buck-Boost transformers can supply a larger kVA than the rating, but I'm having a hell of a time figuring out how to choose the correct winding current depending on the arrangement. We're always using 2 winding buck-boost for our labs and calculations, so I know the rated kVA is across 2 separate windings, and depending on series or parallel configurations, it's going to change things. This video has helped a fair amount, thank you. I'll see if I can find more on your channel and subscribe.
I'm not seeing how you can get an output power more than the input. If volts increase or decrease through magnetic addition or subtraction then amperage would be inversely proportionate, ie, volts going up means amps must go down. If the windings in the primary are good for 25 amps when it's in series with a secondary with 125 amps, it seems illogical to stuff 150 amps through a 25 amp winding.
I'm still trying to wrap my head around this stuff, but the 150A supply side current isn't directly through the 25A rated primary winding -- it's being split with the secondary 125A rated winding due to the configuration (125+25 = 150), so it's not overloading the winding. It's also not supplying more power than the input, the VA value is equal on both sides. Again, I'm suffering through class trying to grasp how these kVA values work because I have similar mental blocks as you (at least you 8 months prior to this reply!).
It does from neg to pos but in AC it'll be both directions. You can pick any direction and it will still work out the same as long as you follow that path
I believe the use of “positive” and “negative” in this discussion was a bad choice. By most conventions H2 would be neutral, or the grounded conductor (US National Electric Code term). I wouldn’t call it “negative”. If your 600V is phase to phase (which is likely would be), then using the “dotted” winding notation would have been a better why to represent it, especially if the viewer has read any buck-boost transformer literature.
This is the same way we learn it in electrical school. The point of using pos and neg polarities is so you can draw the circuit as 2 batteries to figure out the load voltage and amperage.
I need BUCK BOOST TRANSFORMER designing of 40KVA stabilizer 3phase Input voltage range: 340 to 500 volts Output voltage : 400 volts And I need TAP POINT of variable transformer. Copper winding
Think i'm not understanding how transformers works, My impression is that the secondary coil doesn't have a polarity until connected? therefore how can we infer if its boost or buck?
Do I understand correctly then, that a bucking transformer isn't a particular type of transformer design as such, so much as a conventional transformer used in a particular way? If so that would explain why I cannot find any listed in component catalogues!
The connection draws the "first" 600V directly from the input before the transformer, then the transformer adds or subtracts it's secondary voltage of 120V to/from the 600V of the input. The key here is that most of the power does not pass through the transformer, instead only the 120V which is 120/600 = 1/5 of the input voltage passes through the transformer, and the transformer is limited to a maximum output current of (15000/120) = 125A. Thus the output can consume 125A from the input in both buck and boost connection with the difference only being that in buck the output voltage is subtracted from by 1/5 to 4/5 of the input voltage, and in boost the output voltage is added to by 1/5 to 6/5 of the input voltage. Since the kVA going through the transformer is the same in both cases due to the secondary side current being identical, the observation that in buck connection the output voltage is 4/5 of the input voltage where 1/5 corresponds to 15kVA giving 4/5 => 4 * 15kVA = 60kVA, and in boost connection the output voltage is 6/5 of the input voltage where 1/5 corresponds to 15kVA giving 6/5 => 6 * 15kVA = 90kVA. I just watched the video to learn to understand how it works myself, I hope that my explanation is not too far off, and not using too bad naming conventions, it was many years since I last studied any of this :)
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It's really difficult to find any good articles or videos about kVA calculations for these circuits. I'm in a program now trying to get my head around it -- I know autotransformers and therefore, Buck-Boost transformers can supply a larger kVA than the rating, but I'm having a hell of a time figuring out how to choose the correct winding current depending on the arrangement.
We're always using 2 winding buck-boost for our labs and calculations, so I know the rated kVA is across 2 separate windings, and depending on series or parallel configurations, it's going to change things. This video has helped a fair amount, thank you. I'll see if I can find more on your channel and subscribe.
WOW!!!! THIS IS A FANTASTIC TUTORIAL!!!! WELL DONE!!!!! THANK YOU!!!!
Best description I've seen on this. Thanks.
Very good info, the only one i found useful on youtube. Thank you.
Do you have a video or description on how to size a buck boost transformer?
SwirlVanHalen I’m glad you liked it. I don’t right now but I can definitely add that one to the queue.
just want to thank you for all the videos, you're the only reason I"m passing second year right now ahaha
Where ya going to school?
same! I'm in the middle of 2nd year right now in Canada.
Keep it up! You're absorbing more than you think you are.
Very helpful, thank you!
You're very welcome.
I'm not seeing how you can get an output power more than the input. If volts increase or decrease through magnetic addition or subtraction then amperage would be inversely proportionate, ie, volts going up means amps must go down.
If the windings in the primary are good for 25 amps when it's in series with a secondary with 125 amps, it seems illogical to stuff 150 amps through a 25 amp winding.
I'm still trying to wrap my head around this stuff, but the 150A supply side current isn't directly through the 25A rated primary winding -- it's being split with the secondary 125A rated winding due to the configuration (125+25 = 150), so it's not overloading the winding. It's also not supplying more power than the input, the VA value is equal on both sides.
Again, I'm suffering through class trying to grasp how these kVA values work because I have similar mental blocks as you (at least you 8 months prior to this reply!).
doesn't current travel from - to + instead of + to - as you said in the video??
It does from neg to pos but in AC it'll be both directions. You can pick any direction and it will still work out the same as long as you follow that path
Yes - to +
I believe the use of “positive” and “negative” in this discussion was a bad choice. By most conventions H2 would be neutral, or the grounded conductor (US National Electric Code term). I wouldn’t call it “negative”. If your 600V is phase to phase (which is likely would be), then using the “dotted” winding notation would have been a better why to represent it, especially if the viewer has read any buck-boost transformer literature.
This is the same way we learn it in electrical school. The point of using pos and neg polarities is so you can draw the circuit as 2 batteries to figure out the load voltage and amperage.
I need BUCK BOOST TRANSFORMER designing of
40KVA stabilizer 3phase
Input voltage range: 340 to 500 volts
Output voltage : 400 volts
And I need TAP POINT of variable transformer.
Copper winding
Helpful
now i know what is a buck and what is a boost. yay
Love your videos! Thank you for teaching me the things my instructors were supposed to.
Good teaching. Extremly simple and clear.
Think i'm not understanding how transformers works, My impression is that the secondary coil doesn't have a polarity until connected? therefore how can we infer if its boost or buck?
Do I understand correctly then, that a bucking transformer isn't a particular type of transformer design as such, so much as a conventional transformer used in a particular way? If so that would explain why I cannot find any listed in component catalogues!
PS thanks - great video!
How can you draw 60KVA of power on the primary if the transformer is only rated for 15KVA?
The connection draws the "first" 600V directly from the input before the transformer, then the transformer adds or subtracts it's secondary voltage of 120V to/from the 600V of the input. The key here is that most of the power does not pass through the transformer, instead only the 120V which is 120/600 = 1/5 of the input voltage passes through the transformer, and the transformer is limited to a maximum output current of (15000/120) = 125A. Thus the output can consume 125A from the input in both buck and boost connection with the difference only being that in buck the output voltage is subtracted from by 1/5 to 4/5 of the input voltage, and in boost the output voltage is added to by 1/5 to 6/5 of the input voltage. Since the kVA going through the transformer is the same in both cases due to the secondary side current being identical, the observation that in buck connection the output voltage is 4/5 of the input voltage where 1/5 corresponds to 15kVA giving 4/5 => 4 * 15kVA = 60kVA, and in boost connection the output voltage is 6/5 of the input voltage where 1/5 corresponds to 15kVA giving 6/5 => 6 * 15kVA = 90kVA.
I just watched the video to learn to understand how it works myself, I hope that my explanation is not too far off, and not using too bad naming conventions, it was many years since I last studied any of this :)
@@danielnilsson2076 That makes perfect sense! Sir, I thank you.
bravo