15 minute Tech Talk - August 4, 2020 - 30kVA Transformer

In this session we will focus on selecting OCPDs and Conductors for primary and secondary of a 30kVA transformer.
References will be made to the 2020 National Electrical Code.

[@joeballard3027]

Great video!!!!!

[@AlfredoSuarez-rl3qf]

Thanks for this video.

[@TDUNPLUGGED]

Really glad you liked it.

[@educationpower1823]

Very good. Thank so much very clear and accurate 👌

[@TDUNPLUGGED]

Glad it was helpful! Thanks for the feedback.

[@RonaldJamesR]

hello I would like to see the actual wiring process of selected conductors. thank you

[@rogers2339]

I am also waiting for this

[@sinclairelectricws]

Good job

[@TDUNPLUGGED]

Thanks

[@TheVinesettj]

Does anyone know how a #3 Conductor satisfies 215.2(A)(1)(a) in this case?

[@tomasvazquez4804]

Suscrito

[@loloramogayane4044]

Hello ,can i connect 30KVA /400V on a 220V ac source?

[@tomasvazquez4804]

Gracias me gustaría ver más de estos vídeos y también que tipo de interruptor abcd etc

[@TDUNPLUGGED]

De nada. No olvides suscribirte y seguir recibiendo ideas para que pueda desarrollar programas futuros.

[@paulhigdon5435]

I have 480 going into a 100amp breaker ...was going to take #3 copper to my primary 30kva transformer and 100amp circuit breaker on secondary 120/208y panel. do I really need to down size my breaker to a 90? on primary or could I leave the 100amp ....

[@TDUNPLUGGED]

The highest setting you are permitted by Code is Article 450 Table 450.3(B) is 250%. You can't go to the next higher ampere rating like usual as per the notes in the footer of that table. So you can't exceed 250% of the primary FLA in the OCPD size.

[@garbo8962]

Seems like over kill. A 30 KVA transformer @ 480 volts only draws 36 amps. At 125% that is only 45 amps. I would go witb #6 guage copper wire if run was not long.

[@garbo8962]

Let me give you a quick cheater multiplier for finding amps for a 3 phase 480 volt load. Just muitply the KVA by 1.2 . This is within 99.8% of using book formula.for 240 volt 3 phase multiply by 2.4 . easy peesy . Use to blow fellow sparkies minds. Before they had calculator on would give them the answer. Before I retired used to have a lot of single & 3 phase motor amps memorized. Example a plain vanilla 100 HP 3 phase 4 pole ( 1750 to 1770 RPM } motor draws around 125 amps so a 10 HP 480 volt 3 phase draws around 12.5 to 13.5 amps.

[@garbo8962]

@@TDUNPLUGGED in my 50 years I never went 250% higher for a transformer circuit breaker. Saves a lot of money say if you can use a 90 amp breaker versus a 125 amp breaker. Even with high lock rotor amp motors like air & refrigerant compressors, crushers and centrifuges always used a breaker no more then 175% ( except fire pumps ).

[@earleclemans4836]

Can you hook up backwards to stepup voltage?

[@Impedancenetwork]

Of course you can. That transformer can step up or down.

[@paulhigdon5435]

will it really trip it or is that just code

[@TDUNPLUGGED]

Hey Paul. not sure which part you're talking about but if it is the arc reduction methods then it all depends on the arcing current as it relates to the upstream device. We have IEEE 1584 to go on and use that to determine the arcing current and we use manufacturer curves to determine clearing times. Hope this helps. Take care and stay safe.

[@1972hattrick]

Why didn't you take 10% away from the impedance value of the transformer?

[@TDUNPLUGGED]

Just simplicity of the math. I should have mentioned it though. I will bring this up during our session this Thursday. thanks for catching that!!!!

[@lorenzomadam6669]

TSDN? Tom S Domitrovich Network?

[@TDUNPLUGGED]

Technical Social Distancing Network