Electrical basics

[M.Kong-Sivert]

I've been trying for years to convince my team to solder the wires or use heatshrink or both, since our connections kept coming loose, but, while we were talking to some people at a conference, someone gave us a few of these: https://www.wagobox.com/shop/wago-22...412-20pcs.html

We were a little skeptical, but we tried replacing some of our connections with them, and they worked perfectly. If you're not careful, they can pinch your fingers, but they're easy to use, they don't come loose, and they're reusable. We bought a box of them and used them on our robot, and I haven't brought up soldering or heatshrink to my team since then.

If you must crimp, though, make sure the people know how to do it properly. Too many of our connections have come loose because someone didn't crimp the right way.

[Richard Wallace]

Originally Posted by M.Kong-Sivert

...someone gave us a few of these: ...

AndyMark has them. (link)
They work well.

[Al Skierkiewicz]

They are only rated for 32 amps.

[Michael Hill]

Originally Posted by Al Skierkiewicz

They are only rated for 32 amps.

Hey, could you shed some light on current/power ratings for me? Something that's always confused me are ratings at high voltages. These say they're rated for 32 Amps @ 400 Volts. Are these the maximum for both current and voltage? That is, you should neither operate above 32 Amps OR 400 Volts? Or is it it a power rating? That is, it's rated for 32 Amps * 400 Volts = 12.8 kW. Or is it a P=I^2*R power? In that case, the current would be the max current no matter the voltage

[Al Skierkiewicz]

Micahel,
The insulation is rated to withstand 400 volts without arcing through the material. If you were to use this for line voltage it would not cause a safety hazard if handled or attached to metal. (line voltage of 120 volts is the RMS rating not the peak.) The current rating is based on temperature rise using continuous current (usually for 24 hours) If you exceed the current, the device will warm and the max voltage rating will likely fall. Once you exceed the melting point of the plastic, it will deform bringing the conducting parts closer to the surface. While CIM motors in an efficient design won't run at 32 amps continuous, under certain conditions, you may exceed that for several seconds to a minute. In that case, high temperature will result. In addition, the temperature will likely also effect the holding tension device and may just release the wire. Your mileage might vary.

[Aren Siekmeier]

Originally Posted by Michael Hill

Hey, could you shed some light on current/power ratings for me? Something that's always confused me are ratings at high voltages. These say they're rated for 32 Amps @ 400 Volts. Are these the maximum for both current and voltage? That is, you should neither operate above 32 Amps OR 400 Volts? Or is it it a power rating? That is, it's rated for 32 Amps * 400 Volts = 12.8 kW. Or is it a P=I^2*R power? In that case, the current would be the max current no matter the voltage

The current rating of a conductor is itself a power rating, basically how much power can it dissipate as heat. The power dissipated as heat is indeed P=I*V, but this V is the voltage drop across the conductor, not across the load the conductor leads to. The voltage drop across the conductor is given by V=I*R for a conductor resistance R, the power rating is P=I*V=I^2*R, and depends only on the current and the physical characteristics of the conductor (size, resistivity, length...).

The voltage rating of the device is the max voltage before the insulation between conductors or between a conductor and the outside breaks down and allows a current. This is entirely a function of the various dielectric and insulating materials being used between conductors and the electric fields they can withstand before ionizing and carrying a current. The current carried by the insulating conductors has no effect.

So these two ratings are unrelated. You should not exceed either of them, even if you are way under the other one.

[Richard Wallace]

Originally Posted by Al Skierkiewicz

They are only rated for 32 amps.

Or 20A, as stated on the bag -- I think the figure depends on which agency basis is used.

Also the WAGO lever nuts are only sized for 12 AWG and smaller wire -- not really big enough for the 10 AWG many teams (like mine) prefer for drivetrain circuits. We will probably stick with 45A APP connectors for the drivetrain.

[Al Skierkiewicz]

When possible we connect the motors directly to the speed controller by placing the controllers near the motors they drive. This eliminates another connector and therefore another possible failure point. We use screw mount push on connectors on Victors and Jaguars.

[Ken Streeter]

Originally Posted by Al Skierkiewicz

We use screw mount push on connectors on Victors and Jaguars.

These sound neat. I don't think I've seen these before. Can you provide a pic and/or a supplier/part number?

Thanks!

[Al Skierkiewicz]

http://www.digikey.com/product-detai...7866-ND/293277
We buy one hundred at a time. When needed we use the APP 35 and 45 amp contacts. Crimper is available from West Mountain Radio (outside Milwaukee) as well as other places.

[RonnieS]

Will you still be doing this with the limited length of leads on the new speed controllers? Or splicing in on the PD board side?
-Ronnie

[Al Skierkiewicz]

We will likely add APP connectors to the new speed controller output wiring. I don't like that but we will adapt. I hate adding another point of failure.

[JamesCH95]

Here is a good thread to read if you're having issues with your wiring connections: http://www.chiefdelphi.com/forums/sh...d.php?t=119549

There is absolutely no need to both crimp and solder every electrical connection. Crimping is just fine when it's done properly. I would strongly encourage you to do rudimentary tension testing on a couple crimped fittings. They should be able to sustain far more force than one can every apply by tugging on the connection by hand. Ratcheting crimpers are key to ensuring consistent and strong crimped connections.

[Al Skierkiewicz]

James,
We crimp then solder for one very good reason. We lost a World Championship to Beatty when one of our crimp connections let loose. We have vowed that will never ever happen again.

[JamesCH95]

Originally Posted by Al Skierkiewicz

James,
We crimp then solder for one very good reason. We lost a World Championship to Beatty when one of our crimp connections let loose. We have vowed that will never ever happen again.

What would you have done if it was a cold or improperly soldered joint to blame?