TRANSFORMER POLARITY: Everything you need to know

[@SolarElectricGuy-qw8sx]

nice and perfect

[@hilineacademy8482]

Thank you 👍

[@eclecticlearner5943]

Your instruction is clear and unassuming. Very solid video. Thanks for sharing your knowledge my friend!

[@hilineacademy8482]

Yes sir thanks for the encouragement. I appreciate it. 👍

[@612murderapolis]

you explained it better than my njatc transformer book straight to the point.

[@hilineacademy8482]

Thanks man. I appreciate it. If you ever have any questions please reach out. Stay safe. 👍

[@CharlieDelaCruz-ki7cx]

Now I understand. Keep the Good work.... God bless Us.

[@hilineacademy8482]

👍let me know if you have any questions. I’ll get back to you but it might take a while.

[@tedlahm5740]

This is EXTREMELY INFORMATIVE.

[@abelvindas2634]

great video, thank you so much from Costa Rica

[@hilineacademy8482]

Any time. Stay safe 👍

[@luismota9846]

Thank you for sharing your knowledge. I took a course about NEC and when the instructor got to the point to explain transformers I really couldn’t understand anything polarity subtracting or additive 😅

[@hilineacademy8482]

lol. Ya I hear ya. If you have any questions please don’t hesitate to ask.

[@benjurqunov]

Nice ! It's similar to how I determine windings on a 3Φ motor. I'd never given thought to how a transformer applies.

[@hilineacademy8482]

That’s interesting.👍 stay safe.

[@Rkoest]

Hey Cody, what is the functional difference between an additive and subtractive transfer? Meaning, what difference does it make when the primary winding is wound in the same direction as the secondary winding or if they are wound in opposite direction?

[@hilineacademy8482]

So. In the lower primary voltage transformers there’s not a lot of functionality to it. They had to make a standard, meaning that transformers with a primary voltage input of 8660 volts and above will be wound subtractive only because there is an option of winding them one of two ways. In the higher primary voltage transformers there are advantages to keeping a lower difference of potential on the same side of the transformer for insulation purposes

[@denverbraughler3948]

⁠Insulation is a reason to make subtractive winding standard. Insulation doesn’t explain why VA requirement is a consideration.

[@electricalfield22]

Thank you so much sir. That's very informative 👏

[@hilineacademy8482]

👍any time.

[@jeffreykornspan9053]

nice demo

[@hilineacademy8482]

👍

[@shieldcracker]

Awsome video! Please confirm if the 8660V voltage requirement is a line-ground or line to line voltage.

[@hilineacademy8482]

So the 8660 rule is in reference to the voltage that the transformer is asking for. For example Nameplate 8660/14981Y The transformer is asking for 8660 volts so the polarity would be subtractive since it meets the subtractive qualification.

[@sylvansmith3091]

GE distribution transformer books says 200kva AND smaller, 8660v AND below are additive.

[@MizzCupcake244]

I have two books that go over polarity tests and both jumper from H1 to the left bushing. You're jumper uses the H2 instead... can you elaborate?

[@hilineacademy8482]

Great question! When doing a polarity test it doesn’t matter whether you jumped out the two left bushings or the two right bushings. The important thing is that your jumpering out bushings on the same side of the transformer. You will get the same readings on a volt meter either way. Stay safe. 👍

[@James-ql8bo]

On a 277/480 overhead TX would the amp rating be the same as you parallel a 120/240 TX.

[@jasonkenney5970]

If you had a single bushing transformer, could you hook up your 120v to the H1 and the case ground as opposed of the H2?

[@hilineacademy8482]

Absolutely. I would hook up the hot 120 to H1 and the neutral to the pot lug (H2). Then jumper out the case to the secondary bushing on the right. Then measure with a volt meter between H1 and the left secondary bushing. Stay safe. 👍

[@tedlahm5740]

Wonderful But looking for the explanation as to why NEEDED? Under stand the rules over 200 KVA need subtractive transformer, but why?

[@hilineacademy8482]

Great question. The need for larger transformers to me subtractive has more to do with building them. Without getting too much into it. It is beneficial to the transformer manufacturers to make them subtractive because the insulation needs are lower on subtractive cans. We don’t see the benefits on the distribution side as much as they do on the big power transformers where here voltages are larger.

[@CameronPellecer]

Is the H2 in this example grounded during the polarity test? Or did you energize both primary bushings?

[@hilineacademy8482]

So I applied 120 volts to the primary side. Phase in H1 and neutral to H2.

[@denverbraughler3948]

A transformer primary coil always requires two connections with a potential difference in order to be energized. Therefore, at least one connected phase must be ungrounded. The bushings are hollow insulators that guide conductors from the coil through the case to a safe stand-off distance for the terminals. Being insulators, transformer bushings technically cannot be energized.

[@tedlahm5740]

X1 bushing on right side means additive transformer

[@hilineacademy8482]

Correct👍

[@jovetj]

What is the practical application of this? Correct 3-phase wiring?

[@hilineacademy8482]

I am a journeyman lineman and also teach transformer theory at my local apprenticeship. I started this channel so that I could help other journeyman and apprentices learn how to wire transformer banks to supply three phase power to customers. Thanks for watching. Let me know if there’s any questions I can answer. Ide love to help. 👍

[@RHall-xh3ek]

What if your transformer is 23900/13800 x 13800/7979 dual voltage? Is additive or subtractive?

[@hilineacademy8482]

Awsome question. With dual voltage transformers, the manufacturer will base polarity off of the larger voltage requirement. In other words, since this transformer can be fed with either 13.8 or 7979 volts, they would make it a subtractive transformer because 13.8 is over the 8660 volt qualification. 👍

[@benjamenclemenal.5523]

What if the suply is single phase 220v. 10kva a.c. alternator and the secondary output we need 50kw. What kind of tranformer we buy.

[@denverbraughler3948]

@@benjamenclemenal.5523: You would need a magical transformer to meet your impossible specifications.

[@david7three]

@@hilineacademy8482this helped me understand my scenario so much

[@jovetj]

What are the specs on that nice little transformer? Where can someone get one?

[@hilineacademy8482]

It’s a 120 primary to 120/240 secondary. I bought some 1/2 kva transformers that had blown up. Then drained the oil, pulled the cores, and rewound new coils for them. It was a lot of work. I still have to wind some 208 primary to 120/240 secondary. I’ve just had a lot going on and haven’t had time to do it. 👍

[@alexhudson2621]

Will you not change polarity if you swap the high sides?

[@denverbraughler3948]

No. Polarity is relative between the ungrounded primary phase and the secondary phase. If you move the primary ungrounded phase, you measure from it to the corresponding secondary phase, e.g., H1 - X1 or H2 - X2. Swapping H1 and H2 doesn’t really change the measurement.

[@jonbaldwin]

Why not just make all transformers subtractive?

[@hilineacademy8482]

Lol. “How does the posi track on a Plymouth work? It just does” That’s a great question and one that I have asked a few transformer manufacturers myself and the answer I’ve gotten in return is “tradition”. They all say that this is the standard the industry came up with and this is the way the industry will continue to do it. In other words this is what the industry came up with and to change it up now would just be a ton of un needed work. This is the standard and we can just teach the standard rather than wasting the time to dumb it down even further. Stay safe and don’t hesitate to ask questions. 👍

[@daviddaley3007]

We heare in jamaica would say step up and step down tranformer

[@hilineacademy8482]

Yes sir. Where do you work in Jamaica? I went to Jamaica a few years ago and did a climb for gelco belts with Tom Jeffers. I wonder if I met you.

[@denverbraughler3948]

Step-up / step-down indicates the direction of energy flow. It doesn’t have anything to do with the direction/polarity of primary versus secondary windings.