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Controlling the Machine is no longer being updated. Don't worry, though, you can still follow Nate Holt at his new blog, AutoCAD Electrical Etcetera. You'll find it at http://nateholt.wordpress.com. Or you can subscribe to his feed to get latest words of wisdom automatically: http://nateholt.wordpress.com/feed/. You also can continue to view the Controlling Machine archives for Nate's AutoCAD Electrical tips and tricks.
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Calc Motor FLA and Starter Size - AutoCAD Electrical
March 8, 2008, 07:32 PM Nate HoltPick on a 3-phase motor schematic symbol and auto-calculate the minimum starter size. This sample utility was used as an exercise during the AutoCAD Electrical API session at AU07. It illustrated how to use some of the "API" calls built into AutoCAD Electrical and did something useful as a bonus.
Pick on a motor schematic symbol. The utility looks for attributes on the symbol identifying the motor's incoming line voltage and size (HP or KW). If not found, it pops up a small "DCL" dialog to prompt you to supply the missing information.
It then goes into some data pulled from the NEC National Electrical Code to estimate full load amps. It bumps this FLA value up by an extra 25% (per NEC code requirements) and then does a lookup on NEMA starter size and wire ampacity. It finds the minimum wire size that supports the motor's required FLA value. Then it prompts the user to pick the wires that tie to the motor. The utility flips these wires to the appropriate "ampacity" wire layer name.
Running the utility
(Download and copy the two files as described below)
Let's say you have some motor circuits on the active drawing. Here's one of them.
APPLOAD the motwire.lsp utility. Then type MOTWIRE [Enter] at the command line. Pick on this AutoCAD Electrical motor symbol. This small dialog now pops up (defined in the 2nd file you downloaded, motwire.dcl).
Enter in HP and voltage values and hit OK.
The utility now does a quick lookup on full load amps for this 7.5 HP motor at 230 VAC. It multiplies by 1.25 and then does a lookup for the minimum wire size and NEMA motor starter size. Key information is then pushed out to the symbol's RATING1-RATING4 attribute values.
And, in the command window, it prompts you to pick the wiring to the motor so that the utility can flip the wire layer to BLK_10_AWG, the approprate minimum wire size for this FLA rating.
All of the above was covered in our session together at AU07. If you want to take a look at this utility to see how it integrates with a number of the AutoCAD Electrical "API" calls, download these two files:
files/21001_21100/21027/file_21027.lsp (rename motwire.lsp)
files/21001_21100/21028/file_21028.dcl (rename motwire.dcl and put it somewhere in your ACAD support path)
Please modify this utility to make it do more cool stuff.
Comments
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March 21, 2008 04:24 PM RAYMOND GARDNER
This looks really interesting. Is there a DWG file that can be downloaded for trying it out? Where does the original motor "block" come from? Ray
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March 24, 2008 02:21 PM Nate Holt
Hi Raymond, If you have AutoCAD Electrical installed, select the WDDEMO project and open drawing demo02.dwg. I think that's the basis for the screen shots in the blog posting. The motor "block" is one of the symbols that comes with the AutoCAD Electrical package. It is just a generic block with some attributes that the utility keys off of. I suspect that you could modify your own block to be compatible with this utility or you could modify the AutoLISP routine to be compatible with your non-AutoCAD Electrical motor symbol block.
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