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Free Transformer Chart |
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Last month we provided you with a Motor Wire and Protection Chart. This month Mike would like to share with you this free Transformer Chart – should be an excellent tool for use in the office, on the job site, or in a training facility.
Click here or on the image to download the chart. Please print it out, give it a go, and give us feedback on its use and how it can be improved.
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| Copyright© Mike Holt Enterprises of Leesburg, Inc. All Rights Reserved This article is protected by United States copyright laws and may not be published without prior written permission. |
| Mike Holt Enterprises of Leesburg, Inc. 3604 Parkway Blvd. Suite 3 Leesburg, FL 34748 |
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"... as for me and my house, we will serve the Lord." [Joshua 24:15]
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Comments
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On your transformer chart, in the three phase area, you have
3a Wire, 4b Raceway, and 5. EGC while on the 208 volt side,
you have 3b Wire, 4b Raceway and 5. Are these correct and
if so where is the corresponding notes at the bottom as
there is no 3a or 3b and 4a and 4b has to do with wire size
and not raceway. Just a little confusing... Howard January 25 2016, 4:38 pm EST
Reply to this comment |
Reply from: Mike Holt January 26 2016, 9:02 am EST
You are correct, I revised the single-phase table titles, but not the three-phase. We'll update right away.
Reply to Mike Holt |
I have become a Journeyman electrician in 1987. In 1999 I purchased one of Mike Holts books. I read it and it has helped me. In 2014 I reread it and took the Masters exam in the state of Michigan and passed. I have since been a fan of Mike Holt books and teachings.
One problem that I still have is when calculating loads and applying all that I have learned and I come up with something different than the manufacturer has installed to their equipment that I am hooking up and responsible for.
example: I have a 12.5KVA Load at 230vac single phase. It goes to a Mag plate to hold dies in a CNC mill. Voltage available is 480vac. This Magnet is a continuous load. After my calculations the load comes in at 32.5amps @ 480vac. So I would size the conductors with a #8awg THHN
on the primary of a 12.5KVA. This is what I believe to be correct for the primary. The Secondary current came out to be 67.92amps at 240vac. This would require a #4awg THHN. However, when I looked at the unit the manufacturer has placed a single phase #10awg 3 conductor Cable on the output to the mag unit. I will call Manufacturer soon however, I was hoping to get comments on others who have run into this problem. Robert Lane January 24 2016, 3:11 pm EST
Reply to this comment |
Reply from: Wyatt January 24 2016, 8:32 pm EST
Load: (single phase)
12.5 Kva @ 240v. 1/p = 52 A (for a 480-240v transformation.)
12.5 Kva @ 230v. 1/p = 54 A (for a 460-230v transformation.)
I don't think 12.5 Kva is a "standard" rating for the transformer. The nearest sizes are 10 Kva and 15 Kva. Maybe you can get a "special" ?
Reply to Wyatt |
Hi Mike, Could the 15KVA, 208V 3 phase secondary be 60 amps (not 50 amps)to match standard panel sizes? Chris Esslinger January 24 2016, 8:11 am EST
Reply to this comment |
Reply from: Mike Holt January 24 2016, 12:06 pm EST
Yep, can do and will do. I'll send out an updated table in the next few weeks.
Reply to Mike Holt |
How come no 600 V ? It is a Code Recognised voltage (347/600). Jim Green January 22 2016, 9:17 pm EST
Reply to this comment |
Reply from: Mike Holt January 23 2016, 5:54 am EST
What percentage of installations in the USA use this secondary voltage? I've never seen an installation in over 40 years. If you do see these, where, and what loads are served? What type of industry and where in the world?
Reply to Mike Holt |
This is not a comment need some info what circuits in a dwelling require arc fault breakers marco January 22 2016, 10:12 am EST
Reply to this comment |
Reply from: Mike Holt January 23 2016, 7:25 pm EST
Comments not related to the newsletter need to be posted on the Code Forum at www.MikeHolt.com please.
Reply to Mike Holt |
Mike,
When you released the former version of the motor tables, I called your attention to the fact that 240.6(A) tells that ?Additional standard ampere ratings for fuses shall be 1, 3, 6, 10 and 601?. Please note that in the updated tables, this was considered for the single-phase motors, but not for the 3-phase motors. Any reason for that?
Jacob Mendelovici Jacob Mendelovici January 22 2016, 9:06 am EST
Reply to this comment |
Reply from: Mike Holt January 23 2016, 7:34 pm EST
Sorry, will fix my friend!
Reply to Mike Holt |
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