Nate Holt's Blog

July 8, 2015

3-phase Circuit insertion with a pre-defined Wire Connection sequence

Filed under: Electrical — nateholt @ 2:26 pm

Here was an interesting problem. A user wanted to quickly (with a click or two) “ground out” unused CTs shown on a schematic symbol for large power circuit breakers.

blog_xfmr_wire_seq01

Not too difficult to add a shorting circuit automatically… using AutoCAD Electrical’s “Insert Circuit” API call (c:wd_ins_circ2…) in a small Lisp utility. The circuit consists of just the interconnected wiring and attached ground symbol to do the job.

blog_xfmr_wire_seq03

User runs a little lsp utlity, picks on the left-most upper or lower CT wire connection point of the circuit breaker symbol. Utility finds the closest wire connection X?TERMxx attribute to user’s pick point on the breaker symbol, picks the appropriate grounding circuit based upon the X?TERMxx attribute name’s 2nd character (“2″=top connection), and then pops the shorting circuit in, complete with smart ground symbol. Very cool.

blog_xfmr_wire_seq02

But there is a problem with the downstream panel wiring diagram representation of the breaker’s CT connection terminal strips. The user really needs a specific “wire sequence” be applied to the six jumpered wire connections plus ground so that the jumpering on this grounded-out CT’s terminal strip inside the circuit breaker terminal box flows neatly top to bottom. Here is what the user wants to see when the schematic connection information is output to the breaker’s wiring diagram:

blog_xfmr_wire_seq04

But what the user gets is random.

To guarantee the desired connection sequence for the six shorted-out breaker CT connections plus ground symbol means a second step. After inserting the “ground out” circuit, the user needs to find and launch AcadE’s “Edit Wire Sequence” command,,,

blog_xfmr_wire_seq07

,,, and go through the process of rearranging the seven wire connections so that it matches this zig-zag order:

blog_xfmr_wire_seq05

The zig-zag order above will drive the clean jumpering inside the breaker’s terminal box.

Solution

A solution is to predefine a default wire sequence for each set of the six CT connections right on the breaker symbol itself. Push the wire sequence Xdata on to the hidden X?TERMxx wire connection attribute definitions. When the symbol inserts, the wire sequence data will come in with the symbol. If a ground-out circuit is applied to a group of these six connections on the symbol, the pre-defined wire sequence will kick in. If these CT connections are not grounded out, the existing wire connection sequencing will be ignored / overwritten by the discrete wire connections that the user makes (i.e. connections that are not all shorted together).

But adding the correct Xdata / Xdata values to the attribute definitions at the library level is difficult / tedious.

Lisp Utility

Here’s a little AutoLisp utility to make this task easier. With the library symbol DWG open, appload the little piece of source code shown below. Then type PREDEFINE_WSEQ at the “Command:” prompt and start picking the symbol’s wire connection attributes in the order that you’d like to have as a default if the connections are jumpered together.

blog_xfmr_wire_seq06

The utility places Xdata “VIA_WD_WSEQ” with an incrementing 3-digit value on to each picked attribute definition. This mimics what the “Edit Wire Sequence” command does if operating on it AFTER the symbol is inserted. The advantage here is that you do it one time at the library level. The sequencing for jumpered connections comes in automatically when the symbol inserts.

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