Wednesday, August 11, 2010

DMOC installation (3-phase wiring and grounding strap)

More wiring fun.  The AC24LS motor comes with a giant pigtail already installed containing 3 #2 awg wires which will carry the 3 phases of AC power from the DMOC.  The pigtail is supposed to be fed through a bulkhead fitting in the DMOC enclosure, then the cable lugs are attached to terminals in the enclosure.  In order to make the proper connection to the DMOC I had to pay careful attention to how the shielding connects to the metal enclosure which houses the terminal posts (minimize electrical noise).  The instruction manual makes it sound relatively easy.  Peel back this, cut away the excess that, slide the shield over the grommet, tighten the nut.  Great.
(Preceding photos taken from Azure Dynamics' DMOC Instruction Manual)

Well, not so great.  I didn't take pictures of the process but suffice to say that it was not as easy as they made it sound.  The shield is stiff, and the rubber grommet has to be placed in exactly the right place before you start because it will not slide on the heat shrink covering the 3 wires, and the lugs have to be bent exactly just so in order to match up to the terminals.  But the worse part was the nut that holds it all together.  It's a stamped piece with regular raised portions around the outside for gripping with a pipe wrench.  The problem is that because it is stamped all those raised portions correspond to recessed portions on the inside.  So, when they went back in and cut the threads for the nut the threads disappear over the recessed portion.  So, if the nut is not exactly straight when you're getting it started on the bulkhead fitting it will cross-thread.  And, did I mention that this assembly is stiff?  It was right near impossible to keep the nut straight when trying to get it started.  As a matter of fact, I gave up.

Fortunately, my helper friend didn't give up and had the great idea of unscrewing the bulkhead fitting, putting the shield/wires/grommet/nut assembly onto the bulkhead fitting, then putting the bulkhead fitting back on the enclosure.  Removing the bulkhead fitting allowed us to make sure everything was perfectly straight when starting the nut, so it went on.  Finally.  Whew!  3 hours just to connect three wires.

Here's what it looked like after the saga was complete.

I also connected the grounding strap that came with the DMOC.  The instructions called for it to be connected from one of the mounting feet to a good chassis ground.  Well, I couldn't get it to reach to the chassis, but it would reach one of the big bolts holding the adapter to the bell housing of the transmission.  Here's a horribly out-of-focus picture of the grounding strap attached to the adapter bolt.  The other wire with the yellow lug insulation is a #10 awg wire that runs to the main chassis ground bolt near the accessory battery.
Here's the view from a different angle showing where the grounding strap attaches to the DMOC mounting foot.

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