High amp connections for wiring electric motors
 

I have been doing the plant electrician thing for a while now and settled on the best way to make splices for high amp connections for wiring up an electric motor, also building and repairing my own welding machines.
I wire up everything form little 1hp to 400 horse power motors that run at sustained high power for weeks at a time with out slowing down or stopping.
All use 480v 3 phase AC but same principals apply most are in wet corrosive environments, kind of like a vehicle driven on road in the rain and snow.

The little motors up to 10 horsepower just about always get wire nuts, no thrills there.
Anything over 25 horse can use several different kinds of hardware.
Your 3 go to methods for motor wiring are:
Polaris terminal blocks
Bolting terminal lug connectors together
Split bolt connectors.
Then covered with a few layers of rubber splicing tape and then standard vinyl electrical tape over that, unless the motor has a terminal board inside the pecker head.

My early favorite were Polaris connectors they were fast and easy to use. But they are expensive, can be $20 to $40 each depending on the size and type.
Before that I had mostly used terminal lug connectors bolted together.

Both can heat and cool and loosen over time. Both ring terminals and Polaris blocks use have connections that can loosen, over heat and develop higher resistance over time.

Polaris blocks and ring terminals have a tiny amount of surface area connection compared to just split bolting the wires together.
So, I would have to say the best hardware is just the simple, humble and cheap bronze split bolt connectors as long as you can keep the connection dry. You put the wire strands in direct contact with each other and crank them together with many hundreds of pounds of force. Nothing really beats that.
http://ecomodder.com/forum/attachmen...1&d=1460087693
That's three 2 gauge and a 1 gauge wire connection that handles well over 1,000 amps on my home made spot welder and does not heat up.

But you can not use split bolt to go from copper to aluminum a Polaris connector should be used for that, if you use aluminum. (don't use aluminum)
http://ecomodder.com/forum/attachmen...1&d=1460086416
This is an small alumiconn connector for 10 gauge wire, not a Polaris block but you get the idea.

If you need make multi wire connections (3 or more) that need to stay water tight the hands down choice is Polaris submersion and direct burial rated connectors, they are expensive but so worth it.
http://ecomodder.com/forum/attachmen...1&d=1460085847
This one is about $30 to $40 just to make a single three 1 to 2 gauge wire splice. You simply remove the orange caps and jam the wire up in the prelubed sleeve. Then remove the black caps and crank down on the hex head set screws.

But on the smallest and largest AC motors and most DC motors seem to all use ring terminals on the motor.

That means some times you have to use ring terminals.
This is how I select good ring terminals.
Expensive ones are not always the best ones for the job.
Here are some 4 gauge ring terminals I have. Which one is better?
I bet you can tell which one is the cheap one.
http://ecomodder.com/forum/attachmen...1&d=1460085847
The cheap connectors are a little more water resistant. The more expensive ones are usually built a little heavier.

To make the simple ring terminals more water resistant I crimp them and wrap some vinyl electrical tape around the copper terminal and wire insulation http://ecomodder.com/forum/attachmen...1&d=1460086416
You can also solder them after they are crimped or put some non-ox in the terminal before crimping. There are other ways such as liquid electrical tape to seal up the connection.

great info. thanks for sharing.

I have studied crimp terminals in depth, on a quest to get the lowest resistance connection possible. I tried all kinds of different crimpers, and finally just built my own for use on my 20 ton shop press. By in depth study, I mean build and test, repeat.

http://i1242.photobucket.com/albums/...420_180955.jpg

Here is what a 20 ton crimp looks like on 2/0 welding cable:

http://i1242.photobucket.com/albums/...420_181031.jpg

and here is a cut away view of the inside:

http://i1242.photobucket.com/albums/...420_182840.jpg

This was an earlier crimp. It tested with ultra low resistance, but I did not like how the anvil made such an abrupt transition from the round part of the lug to the squashed part. This one is a little wider and flatter compared to the one above. I was worried about breaking strands inside, so I made that deeper narrower shape above. I did cut them open to inspect the transition, and the taller looking crimp was flawless.

http://i1242.photobucket.com/albums/...418_081853.jpg

At home I use a crimper the size of a large lock cutter with rotating dies that crimps everything from 6 gauge to 3/0 gauge.
The crimper crimps ring terminals down on welding cables that will be used in high vibration and will be getting flexed and pretty much everything else.
Also works great on SB175 connectors.
I usually just crimp them in the middle so there is a smooth transition between flexible cable and the crimp, because I found when they are crimped all the way to the end of the lug strands break like crazy.
Plus I need something a little more portable than a shop press.

I like crimps best as well.
I bought red and black heat shirk with hot melt glue inside to make that water tight seal.

I have a variety of bolt cutter style crimpers, but I always measure higher resistance with those crimps. I tests my connections at 700 amps, and between 100 and 120 volts DC, and this seems to be where resistance variances between my batteries show up the most if the connections are not perfect. I have a real time display of all of my high current circuit connections in my pack that I can watch and record as I drive, that shows resistance and voltage of each connection. When I drive around normally, "good" connections read fine, but when I get up into the 500 to 700 amp range, I can see variances in resistance between each battery. My display has each battery numbered, so I can go right to my highest resistance connection without having to look at all the others. I cut them open, and study them, and then improve on them.

The broken strand thing that you mention is spot on, and I have had to shape my anvils many different ways to make a crimp that is "nice" to all the strands. The edge of the anvil has to be tapered so that it does not cut into the lug and the strands on the other side of the stress point. Here is a proper crimp, view of the non stressed side:

http://i1242.photobucket.com/albums/...421_084812.jpg

Here is a view of that same crimp on the stressed side. Notice the 45 degree cross taper. This is so that I don't shear the strands:

http://i1242.photobucket.com/albums/...421_084832.jpg

I do a cross cut after I chop the connection in half, and this allows me to study the stress point of the strands. I had to make a lot of anvils to finally get where I don't break any strands. You can see some damaged strands where I chopped it in half, but those are from my cutter.

http://i1242.photobucket.com/albums/...421_085834.jpg

I also like to go portable with my crimpers, so I have built one that I can use my 1/2" impact wrench on. I wish I could bring my shop press with me sometimes, but this crimper will do the job when I can't bring it. My shop press crimper does not have those big bolts on the ends like this one does.

http://i1242.photobucket.com/albums/...421_151007.jpg

I confess to having an unusual drive to seek out ultimate efficiency and perfection when I build an EV, and it has shown me things that I suspect most people will never really notice. Without the proper instrumentation, it is not possible to study and record the resistance of every single connection real time,and being able to do this has really taught me the difference between a nice connection and the best connection.

There are efficiency gains to be had with ultimate connections, even if they are not much. The other thing that is important about the integrity of a connection is how well it holds up over time. I have noticed that if I monitor my highest resistance connection over time, the resistance of that connection begins to get even higher faster than the resistance of my other connections. The better the connection, the longer it will last.

In the case of connections in my latest build, My controller is in communication with my BMS via canbus, and is programmed to derate my throttle as needed to prevent any one battery from dropping below whatever minimum voltage I program in. If there is a connection that has more resistance, it is calculated as a voltage drop, and my BMS will identify a lower voltage on that one battery and cut back my throttle to protect the battery. The battery is fine, but the higher resistance will effect the voltage reading. What this means is that I get less voltage sag and delta, and more throttle if my connections are perfect.

Keeping the connection protected is indeed critical. I love mother nature, but we have to keep her out of our connections. If she gets one little taste, she will get addicted and consume it all.

My compliments on your drive and determination to achieve the best results that you can.

I see that you avoid doing what the off-the-shelf dies do - crimping uniformly around the lug, with a hex or octagon shape. You best results are from leaving the lug round on the 'bottom side' and only crimping the 'top' .. right?

For those of us with cheap chinese crimpers .. where the dies are removable and would be quite easy to change out .. do you have a sketch or drawings of your 'best-so-far' profile that you are willing to share?

I would argue that there are many things that are not noticed unless you have spent a lot of time and effort to measure them well. But you have to be willing to invest the time and $$$.

Have you posted details on this BMS yet? I think I've read through all of your posts and I don't remember ... or was this a custom job?

This picture clearly illustrates a "perfect" crimp. See how uniform the copper material appears, with absolutely NO demarcation between the crimp itself and the copper strands, giving the visual appearance of being "one" solid piece of copper:

http://i1242.photobucket.com/albums/...418_081853.jpg

My BMS is an Orion. When I first bought it, I was still back in the frame of mind where a bms is just a piece of equipment that kept the pack top balanced, and had some high and low voltage cut offs. It took me a couple builds to fully grasp what an Orion does, but I am hooked now.

I have tried other crimp shapes, but have not done 8 sides. I messed with 6 sides, but it does not work the way I like with only one linear plane where the dies slide together. I have also done a mirror image of what I posted above on the bottom side as well so that there are two anvil indentations across from each other. The deeper crimp that I posted works out best, and the sides of the crimp actually get squeezed in a little as the anvil forces the terminal to the bottom of the receiving portion, since I made the bottom receiver of my tool have a very slight v shape.

That crimp tests very nicely under load, but you can see the line across the terminal where the anvil mark does not transition as well as it should. It risks shearing strands.

Most of the high power variable frequency drives I work with use a crimp that crimps like that, making a triangular or kind of a chevron shape crimp.

That's a good point .. I should look at what our vendors are doing for their crimps on VFDs. I know that at least one of them is using copper buss bar instead of cabling inside the power section. They can bend the buss much sharper than they can bend cables. Plus the buss is bolted to insulators, so it does not move around or rub against other cables, edges, etc during high current events.

But I have not paid much attention to what they've done with the crimps on the cables that they still use.

The use of bus bars wherever possible is best, since half as many mating surfaces compared to crimp cables. Cables have strand to crimp lug contact, plus crimp lug to terminal, bus bars only have bar to terminal. I like to use bars, even in places where cable could be used.


http://i1242.photobucket.com/albums/...agejpg1-86.jpg

http://i1242.photobucket.com/albums/...gejpg1-111.jpg

Cable would have been tight here. The bus bar is cut to maximize the surface of the fuse though.

http://i1242.photobucket.com/albums/...agejpg1-87.jpg

.

The military seems to like to silver plated hardware.

All the big VFDs use aluminum buss bars.

I think the ultimate efficiency would be copper buss bars that have been silver plated.

The crimps used by allen Bradley in the big drives look a lot like, if not identical to what you have there.

A crimp on a 350 amp VFD
 

An example crimp on one of our older Siemens VFDs

Rated 354 amps continuous at 575VAC

The first pic is of the 3 phases off the bottom of the output bus. Second picture is a close-up of the crimp.

https://www.flickr.com/photos/141097.../shares/yos295

It looks a lot like EVMetro's cut-away

What did you use to slice through the crimp so cleanly? I will attempt to cut a couple of crimps apart to see how good they were.

Another example, 600 amp at 575V
 

2 more pictures with longer lugs and 2 bolts per lug to the phase bus

The crimp-on connectors are longer and the circular crimp does not begin on the edge, but about 1/4 of an inch in. It also stops about 1/4 of an inch from the edge.

https://www.flickr.com/photos/141097.../shares/Xc261q

Example from 4160V vfd, 105 amps continuous
 

Smaller crimps on 5KV rated cable

https://www.flickr.com/photos/141097.../shares/5kez6P

The crimps appear to start at least 1/4 inch from the edge and from the end of the lug

The visible parts of the bus show as copper. The plating appears to be tin?

1600 amp horizontal bus, 600 amp vertical bus
 

This 600V switchgear has 1600 amp bus. The bars are braced for 65,000 amp faults (structure)

The 600 amp vertical bus looks a bit puny by comparison

This has nothing to do with crimping .. the equipment is being de-commissioned so I took the opportunity

https://www.flickr.com/photos/141097.../shares/Hi8Zh3

Buss bars are welcome here.

Wego connectors: "For those in a hurry to burn your house down" I salute you.
With all the electric cars being sold and home charges being installed this seems relevant.

https://youtu.be/zgjo36-jaFY
https://m.youtube.com/watch?v=zgjo36...ature=youtu.be

I have seen them used in industrial settings for years and my conclusion is they aren't worth a beaver dam. For communication and signal wiring they're fine for power wiring no, use wire nuts or or any of the above. Always follow code.