Thursday, March 1, 2018

Re: [Electric Boats] Re: Electric motor Grounding locations

 

 E-11 would have all three grounds connected,  negative from each DC bus and AC ground (green wire) would all be connected via properly sized cables or straps and then connected to the shaft via the brush. Your boat should already have the AC and 12 volt systems bonded. That is normally close to the most negative 12 volt bus.  If you don't want to buy the current ABYC E-11 PDF,  you can probably google "ABYC E-11 pdf" and find an older one some place of the web.   It is pretty easy to read through and will give lots of good advise.  

The above is if you choose to have a common earth ground.  If however you want to float the traction battery pack (48 volt) then don't connect that to the brush or the other two.  But do connect the 12volt and AC to the shaft brush.  Again the cable used should be sized to match the largest cable used to carry current on the pack. 

On Feb 27, 2018, at 12:04 PM, Matt mattkaine@hotmail.com [electricboats] <electricboats@yahoogroups.com> wrote:

 

I ordered the shaft brush you recommended. Just so I'm clear, you are saying the 120AC ground should be isolated from low voltage DC grounds and I should tie the 48vDC and 12vDC grounds together, then connect that to the Shaft Brush? I was under the impression the AC and DC grounds we're supposed to be tied together, so any stray current goes to earth via the shore power ground line for safety. I do have a galvanic isolater on my system just after shore power plug, then ground runs to AC panel ground bus bar, which is connected to DC ground bus bar.

Sent from my Huawei Mobile



-------- Original Message --------
Subject: Re: [Electric Boats] Re: Electric motor Grounding locations
From: "'james@deny.org' james@deny.org [electricboats]"
To: electricboats@yahoogroups.com
CC:


 

For 48 volts and less,  I follow the ABYC E-11 recommendations and have a common ground between all systems.  At higher voltages ABYC TE-30 says keep them separate.  

I personally went with a 48 volt system because I wanted to be able to have a common ground. I don't like having different potentials between different systems that I or a swimmer nearby could be a bridge path between.

More important then if you bridge the two DC grounds together, make sure your old AC system still has earth ground. Most marine systems used the engine block via the shaft to ground to earth.  If your boat does not have another path, once you removed the old engine your entire ground system may be isolated from earth.  

If so a cheap 35 dollar shaft brush will re-earth your system.  See my earth ground bellow:




On Feb 27, 2018, at 10:10 AM, king_of_neworleans <no_reply@yahoogroups.com> wrote:

 

My 48v system is not grounded. General consensus seems to be that this is best. As for grounding the controller, I think tech support at Sevcon can provide a better answer on whether it should be grounded or not. My Kelly controller is not grounded. My motor casing and rotor shaft are incidentally grounded, of course. However phase windings, power supply cables and 48v bank are all floating. Some owners also use a flex coupling to isolate the motor shaft and casing from ground as well, though I don't think it is necessary.



---In electricboats@yahoogroups.com, <mattkaine@...> wrote :

So I just installed a 10kw motor Kit from Trunderstruck EV on my 1976 Islander I-28. I am very happy with the install, works awesome. I am however not sure on best method for grounding new power system. So the current set up is this...I have 2x 12v house batteries with a common ground bus, my 120vAC shore power connects its ground to same ground bus. Now where I am not sure...the 48v motor system consists of 8x 6vDC batteries in series>Power relay>Sevcon Gen4 Controller>motor. Ground bypasses the relay and goes straight to Sevcon. Should I connect 48v bank  to 12v ground bus? Should I run a separate ground from motor frame to ground bus?

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