Thomas, I have been doing basic three phase short circuit calculations for about a decade now. Have believed what my seniors told me about thermal and magnetic effects of high SC (above device ratings) but I must admit that your this piece of work has addressed my "seeing is believing" aspect. The videos of various tests is too good that you shared... Simply loved it to pieces.....Keep up the good work Sir.
Thomas, I'm really enjoying these presentations and have started sharing with co-workers. Thank you for all your time and effort in these videos! Do you have a short video demonstrating 70e category method and associated limitations with equipment being serviced, available fault current, and trip clearing times?
Thanks for the note! Sometimes I wonder if it is worth the time and energy. I know this was from 8 months ago but I am just now seeing this. Thanks. TD
An application where interrupting ratings can easily be mis-applied is on some PV applications involving a customer owned medium voltage to 480V padmount xfmr connected to a multi-megawatt inverter. Often, there's a need for a small amount of 120V power, and this need may be met via the use of a Mini Power Center connected to the 480V xfmr. Those mini power centers normally have interrupting ratings on their main breaker that are too low for the fault current the large xfmr may be able to deliver. Sometimes current limiting fuses are needed ahead of the mini power center.
Hi Thomas on 1:57:05 you talk about using the 10% tolerance even in as built calculations. My question is, if the manufacturer sends me the "Certified Test Report" with an impedance more accurate than the one in the equipment plate, do I still take in account the 10% tolerance?
I failed to understand why at 1:45:15 it was said that you should consider the impedance based on the xfmr's rating if no fans are used, rather than the higher rating if the fans are used. I had understood it that %Z basically is what percent of the xfmr's available short circuit current it is able to deliver at its rated load. So if you take rated KVA and divide that by %Z, then you get short circuit KVA. I fail to understand the statement that %Z would be the same at both KVA levels. To me, the %Z (percent the xfmr is shorted) changes at the higher KVA value. It would seem it would have to be a manufacturer standard to mark the %Z at the lower KVA value and not something of electrical theory that the %Z stays the same.
Can cable limiters ever be used to accommodate lower fault current ratings on equipment? Never seen it done this way but wondered. If it was allowed, I would think there would be concern with parallel runs, of making sure they all operate both for purposes of clearing the fault and also to make sure you don't have just 1 open, creating overload on the other conductors if the circuit survives the fault and is re-energized.
@01.25-26. Utility fault current availability is said to be insignificant in many cases when doing available fault current calculations for equipment compatibility considerations. Infinite bus is used. However, what is its effect on available arcing current? Is it also negligible?
@@markwelte8391 Hey Mark. Yes. I will take attendance in the beginning via a code and the menti web site and at the end you will have teh chance to fill out a short quiz. That pair of info will get ya a cert.
Thomas, I have been doing basic three phase short circuit calculations for about a decade now. Have believed what my seniors told me about thermal and magnetic effects of high SC (above device ratings) but I must admit that your this piece of work has addressed my "seeing is believing" aspect. The videos of various tests is too good that you shared... Simply loved it to pieces.....Keep up the good work Sir.
Excellent presentation. Very complicated topic broken down into chunks that can be understood. Well done!
Just found this one. Thanks for your insight. I always learn something new whenever I watch your stuff. Thanks again!!
Excellent presentation Thomas
subbed
Thomas, I'm really enjoying these presentations and have started sharing with co-workers.
Thank you for all your time and effort in these videos!
Do you have a short video demonstrating 70e category method and associated limitations with equipment being serviced, available fault current, and trip clearing times?
Thanks for the note! Sometimes I wonder if it is worth the time and energy. I know this was from 8 months ago but I am just now seeing this. Thanks. TD
An application where interrupting ratings can easily be mis-applied is on some PV applications involving a customer owned medium voltage to 480V padmount xfmr connected to a multi-megawatt inverter. Often, there's a need for a small amount of 120V power, and this need may be met via the use of a Mini Power Center connected to the 480V xfmr. Those mini power centers normally have interrupting ratings on their main breaker that are too low for the fault current the large xfmr may be able to deliver. Sometimes current limiting fuses are needed ahead of the mini power center.
great work Thomas thank you very much
You are very welcome
Hi Thomas on 1:57:05 you talk about using the 10% tolerance even in as built calculations. My question is, if the manufacturer sends me the "Certified Test Report" with an impedance more accurate than the one in the equipment plate, do I still take in account the 10% tolerance?
I failed to understand why at 1:45:15 it was said that you should consider the impedance based on the xfmr's rating if no fans are used, rather than the higher rating if the fans are used. I had understood it that %Z basically is what percent of the xfmr's available short circuit current it is able to deliver at its rated load. So if you take rated KVA and divide that by %Z, then you get short circuit KVA. I fail to understand the statement that %Z would be the same at both KVA levels. To me, the %Z (percent the xfmr is shorted) changes at the higher KVA value. It would seem it would have to be a manufacturer standard to mark the %Z at the lower KVA value and not something of electrical theory that the %Z stays the same.
Can cable limiters ever be used to accommodate lower fault current ratings on equipment? Never seen it done this way but wondered. If it was allowed, I would think there would be concern with parallel runs, of making sure they all operate both for purposes of clearing the fault and also to make sure you don't have just 1 open, creating overload on the other conductors if the circuit survives the fault and is re-energized.
@01.25-26. Utility fault current availability is said to be insignificant in many cases when doing available fault current calculations for equipment compatibility considerations. Infinite bus is used. However, what is its effect on available arcing current? Is it also negligible?
Can you use up-over-down for higher fault current-reduction at equipment that is rated 5ka? Would this be recognized be nec 110.10?
Thanks, great information! I wish electrical engineers would figure out how to mute their phone.
Where can we get our PDH certificates?
I'll post after I look through the quiz results. I'll send a link to everyone with the file location
@@TDUNPLUGGED - hello...can i get pdh if i watch on youtube? thanks mark welte.....welte@rd-mc.com
@@markwelte8391 Hey Mark. Yes. I will take attendance in the beginning via a code and the menti web site and at the end you will have teh chance to fill out a short quiz. That pair of info will get ya a cert.
@@TDUNPLUGGED thanks Tom!
Somebody is speaking a foreign language 😂😂. He sounded definitely Colombian
Devil man phoenix
Mándale un correo 😂