Dennis Merchant video on transformer polarity. This video goes with 3rd year transformer connections units of instruction in the Merchant Job Training & Safety Program.
Thank you so much for the kind comment John. They were made in the day of VHS Video tapes. We are so glad for a medium like RUclips so that we can share them in a cost effective manner to a wider audience. We know of an instructor at a vocational school who is referring his students, and another instructor working at a power utility that is running some of the videos in class. We have more coming. The transformer videos deserve to be done in a manner where lighting & focus aren't and issue.
At 6:15, the explanation of the vectors and how they are tied is opposite from what is drawn on the board. The first example is of a subtractive transformer, so the vector arrows must point the same direction with H1 and x1 tied together (same potential) making the voltage measurement between H2 and x2 108 volts. The additive example begins around 7:10 where the vector arrows point opposite and H1 and x3 are now tied (same potential) to make voltage between H2 and x1 132 volts. Believe me, he knows his stuff, but is still human! Great videos for in depth learning.
+bbrown86neo thanks for the comment! I would like to suggest something though. Dennis always drew his vectors so that they point to the higher numbered terminal. From H1 to H2, and from x1 toward x2, etc. Try thinking about at how the coils look if they were laid out flat like the vectors. In other words, what if you took out the volt meter, and then flipped the x1-x2 coil out to the left so that the assembly was laying like an open book? The high side vector would point out to the right, and the low side vector would point out to the left, just like he drew them! Think about it. The reason you get 108 volts is because you have 120 volts to the right, and 12 volts pointing out to the left and subtracting from the 120 volts! In other words, the vectors are in opposition! Does it make sense to think about it that way? Let me know. If it doesn't I can draw you some diagrams and email them to you.
This really helped me quite a bit! I was struggling to understand it, and then you drew it in a very understandable fashion. Thank you for this help!
I teach electrical theory at a vocational school. These videos are great! Thanks so much.
Good work. The quality is not so bad. The content is fabulous!
Thank you so much for the kind comment John. They were made in the day of VHS Video tapes. We are so glad for a medium like RUclips so that we can share them in a cost effective manner to a wider audience. We know of an instructor at a vocational school who is referring his students, and another instructor working at a power utility that is running some of the videos in class. We have more coming. The transformer videos deserve to be done in a manner where lighting & focus aren't and issue.
This is the very useful programme. Thank you.
At 6:15, the explanation of the vectors and how they are tied is opposite from what is drawn on the board. The first example is of a subtractive transformer, so the vector arrows must point the same direction with H1 and x1 tied together (same potential) making the voltage measurement between H2 and x2 108 volts. The additive example begins around 7:10 where the vector arrows point opposite and H1 and x3 are now tied (same potential) to make voltage between H2 and x1 132 volts. Believe me, he knows his stuff, but is still human! Great videos for in depth learning.
+bbrown86neo thanks for the comment! I would like to suggest something though. Dennis always drew his vectors so that they point to the higher numbered terminal. From H1 to H2, and from x1 toward x2, etc. Try thinking about at how the coils look if they were laid out flat like the vectors. In other words, what if you took out the volt meter, and then flipped the x1-x2 coil out to the left so that the assembly was laying like an open book? The high side vector would point out to the right, and the low side vector would point out to the left, just like he drew them! Think about it. The reason you get 108 volts is because you have 120 volts to the right, and 12 volts pointing out to the left and subtracting from the 120 volts! In other words, the vectors are in opposition! Does it make sense to think about it that way? Let me know. If it doesn't I can draw you some diagrams and email them to you.
Excellent video!