15 Minute Tech Talk - 75 kVA Transformer

This session will look at a 75 kVA transformer and select primary / secondary OCPDs as well as primary and secondary transformer conductors.
For more information on Eaton dry-type low voltage transformers please see the following link:
www.eaton.com/...

[@geofferyromany4634]

As a newbie on learning about transformers I was a little confused about the formula you used. After re-reading my text and doing the calculation according to the text, I got approx values for primary and secondary current FLA. Happily, I realized that your formula is a shortcut and accurate (within an approx). I will use it in the future for swift calculations. Thx. Good video for newbies like me. Keep it up

[@garbo8962]

Glad you mentioned selective ampere selection. Retired from a large hospital/research center where they talked about this but never did antyhing on it. Several times a zone mechanic was replacing a 277 volt breaker and caused a short circuit where the 225 amp tripped and not the 20 amp branch circuit breaker. This occured in at least 3 large ( 10 to 14 floor ) buildings.

[@TDUNPLUGGED]

Really appreciate the feedback. I have often been told that events like what you described never occur in a hospital. Would love to learn more.

[@carlubambi5541]

This happened to me at York University Campus .3 phase 600v/347V lighting control circuit rated for 20 amp single phase breaker took out the main 3 phase 100 amp lighting control breaker .Crazy stuff happens with impedance drops and AIR ratings of breakers .

[@joeballard3027]

Really like listening to this guy lay down some riffs

[@KevinCoop1]

One of Eaton’s competitors makes 250 amp MCB and 250 amp buss panels as a standard for a good reason. Many times if 250 is specified, their competitors, like your company, couldn’t compete with the price. Economics pay a huge role in the decisions. Especially if you are the contractor and designer.

[@TDUNPLUGGED]

Thanks for joining in the discussion @kevinCoop1.

[@educationpower1823]

Hey Tom. Great job on these tech talks. Robert from Omaha

[@scfc96g]

nice i just put in a 75 kva transformer and panelboard, it was a great tech talk

[@LittleOldBoat]

You got my attention, thanks for your time!

[@TDUNPLUGGED]

Glad I could help!

[@intheskymusic]

Take an hour if you have to brother, great information like always.

[@AlfredoSuarez-rl3qf]

On the field we use 125% calculation for primary and secondary OCPD.

[@AlfredoSuarez-rl3qf]

Thanks for this master class.

[@TDUNPLUGGED]

Sure thing. I agree that 125% is very common. I think a little depth of knowledge helps to understand the why's. You have to love those rules of thumb that get you through some hard parts.

[@educationpower1823]

Your sound is 👍

[@4abettaworld]

Thank you brotha, appreciate you!

[@TDUNPLUGGED]

Any time!

[@RonaldJamesR]

great job. however I would like to see the wiring process. thank you.

[@TDUNPLUGGED]

Hey Ronald. thanks for the feedback. I"ll see what I can do on the wiring. going to have to get a video on that in our experience center.

[@enriquetrujillo7864]

Incredibly informative video thank you

[@carlubambi5541]

STANDARD PRACTICE IS WIRE FOR 125% IN CANADA FOR WIRE SIZE AND NOW SOME AREAS WANT OVERSIZED NEUTRAL .All because of harmonics from VFDs And Switch mode power supplies .Ztrap is optional

[@TDUNPLUGGED]

Thank you Carlu for that note. Very good point on oversizing the neutrals!

[@johnmich1242]

Please do one on TC curves

[@lawoull.6581]

awesome video

[@kevinokuku7289]

Thanks for the video. I have a 30 kva transformer. I need to feed 415vac to the input. I require 240vac at the output and not 120.how do i achieve that?

[@josecruz490]

Great video 👍👍

[@educationpower1823]

Nice job Tom as usual. I thought you needed to supply ocpd to the load possible regardless...

[@TDUNPLUGGED]

Thanks Robert. Yea, that primary OCPD is tricky because you have that pesky little detail called inrush :)

[@marktheunitedstatescitezen185]

Thanks , you really know what you’re speaking ! Any and all advice is welcoming! “ My breaker box in my house is 100A / 120v 2 Phase - I’m installing for electrical back~up only a 5KVA Solar Inverter 230v charge controller 48v PWM what I see is the inverter 230v One Phase the L1 is 115v & the Neural is Hot line of 115v & the ground is a ground ! What’s you’re idea of using the L1 = 115v & the Neutral = 115v into a 20A Double Pole breaker to back-feed my breaker box all One Phase of 115v & the inverter at 5KVA is 86A and my house per month uses between 3-3,500KW a month and I’m going to use a SIEMENS Transformer MTO100A 480-220 input One Phase & Output 240-110 Two Phase ~ Off my Order inverter to the 20A Double Pole breaker . Sounds good ?

[@aten9754]

Wth are you talking about. Better call electrician

[@nisuquayum7817]

for the secondary time i would put 250 amps panel broad

[@TDUNPLUGGED]

Thanks for commenting and adding the value of the video. I agree with you. There are so many options in these applications.

[@danielno20]

What gauge wire did you use for high and low voltage?

[@how2diy123]

So if I am installing a 75kva Step Up i can just use all the info you just provided but just flip info on primary and secondary ?

[@TDUNPLUGGED]

step up transformers are a little different beast. Make sure the transformer is listed for back feeding and as far as I can tell you make the same calculations. Inrush on that will be a little different too. I'll do some research and put a program together as this could be a good discussion on the program.

[@BlackAdam2784]

**Very good video !!

[@rabindranauth1235]

Do you have troubleshooting videos for these transformers

[@sungkim16]

Why is the optimum ocpd 100amps and not 115A

[@TDUNPLUGGED]

sungkim1189, I would agree that a 115A OCPD would be the appropriate solution for that application.

[@KevinCoop1]

115A is not a standard OCPD rating. Standard ratings are 100, 110, 125, and 150 amps. For 35 years, I used 125 amps on 75Kva rated primary.

[@nestorporquirino5595]

LOVE IT 😍🤩👍

[@demetriotizcareno980]

Thanks

[@presicionturning5672]

so can i run a 3phase cnc machine from 1phase power source using this type of transformer? thanks

[@TDUNPLUGGED]

That would take a bit more than just this transformer.

[@nisuquayum7817]

.9 is the efficiency of the transformer

[@TDUNPLUGGED]

Thanks for commenting and adding to the value of the information!

[@emmanueltsey3417]

Please I needed to do a house wiring of both 110v and 220v after it all it was 30 socket in number for the 110v and I want to know the type of the step down transformer to use in order to power the entire room.thank you

[@NancyMendozai]

Davis Patricia Hall Mary Garcia Jeffrey

[@ricsalsa]

x the equation i think u will mixt up people more than anything lol u should put all the numbers on the screen maybe it will help...maybe lol.

[@alammd4673]

😜