Re: Main Power Terminal Blocks?
 

Ah, yes, that clears things up.

thank you
deb

Re: Main Power Terminal Blocks?
 

Michael,
20 amp breakers will not fit into the 40 amp Maxi blocks and you need at least one 20 amp breaker for the RC.
Adam,
Unfortunately, you do need to redo the electrical on this pictured robot. I might add that you have some rather excessive lengths on the primary wiring. Every inch of wire limits the maximum current that can be delivered to your motors. If you simply move the main breaker closer to the pump and turn the Maxi block over so that the ground termination is closer to the inside of the robot you would remove almost 5 ft. of #6 wire I bet.
You will also make inspectors very happy if you could orient the Maxi block so that the breaker labels were visible. Please insulate the battery terminals before doing anything else. Thanks.

Re: Main Power Terminal Blocks?
 

One does not follow the other. Although the blocks may be rated for 85 Amps, the use of a larger wire does not cause any problems. You may safely use any wire up to the maximum for which the connector is rated (#6 you stated)

Using the largest wire possible has advantages, particularly in minimizing voltage drop due to ohmic losses. Of course, it does weigh more, so that's a disadvantage that needs to be considered.

Don

Re: Main Power Terminal Blocks?
 

Thanks Al,
I realized that myself today, when I unpacked everything and looked into the possbility and noticed immediately that the smaller breakers wouldn't fit.(In years past we used the now defunct IFI breaker panel).

So it looks like 2 maxi-blocks, and 1 atc-6 breaker for us this season.

*sigh* It's only one more pound after all. LOL!!!

Thanks again to everyone.

Re: Main Power Terminal Blocks?
 

I see that the most common recommendation for wiring the 120 A breaker, battery, terminal blocks, etc. is 6 gauge wire. Last year however, our robot's 6 gauge wire was hot at the end of every match, leading me to believe that ideally lower gauge wire would decrease the temperature increase of our wires, as well as decrease resistance and voltage drop.

I have not seen any rules saying we can't use 4 gauge, and our team likely will, but does anyone here see any electrical disadvantages and possible rule violations? (The largest factor that may persuade us not to use 4 gauge is that it doesn't fit in some of the given power supply equipment (like the new Power Terminal Strip).

Thanks in advance for the feedback =)

Re: Main Power Terminal Blocks?
 

Chaychay,
The wire guages in the robot rules are minimums as long as you stay with the breakers specified. I have not looked closely at the specs for the terminal blocks, but larger wire may not fit those blocks.
However, if your #6 was getting hot, you had a much bigger problem. Your robot was likely running near the point at which the 120 amp circuit breaker was close to trippin. This is not an auto reset breaker, once tripped you are done. Ther are other possiblities, was the #6 from the battery to connector hot or from the connector to the main circuit breaker or was all #6 hot? In order to raise the temp on all #6, you had to be running close to stall on all motors which means you were drawing well over 200-250 amps and likely was running the battery down in one match.

Re: Main Power Terminal Blocks?
 

Thanks for the feedback Mr. Skierkiewicz!

All the 6 gauge was hot, but the wire from the battery to the 120 amp breaker was the worst. After a hard match (hard on the drive motors) it would be hot enough that I'd say any hotter and the insulation would have become pudgy. (notes: we were using a 2006 battery, 6 gauge provided in kit for power distribution, running 4 CIM's on drive, 1 mini-bike on shooter, and globes/fishers for ball transport through the robot....so we were indeed drawing quite a bit of energy)

We checked our robot post-season to ensure we didn't have any loose electrical connections, (like a loose crimp head creating this abnormal current draw) and found nothing.

(I'm my journeys across the internet I found that www.robotmarketplace.com rates the Anderson Powerpole connectors we use at 50 amps. (they are blue on the the website, but the dimensions match the APP connectors that we are given. (even though we somehow get 6 gauge wire into those connectors)) - just thought that was an interesting tid-bit, I was surprised seeing as we have a 120 amp breaker right after this connector thats only rated for 50 amps.

Anyway, we'll probably be going with 4 gauge (~1000 strand), if your interested in how it works out, or any problems we had/are having along the way, feel free to PM me :) - If anyone has any special tips for working with 4 gauge, let me know, we appreciate it very very much.

Re: Main Power Terminal Blocks?
 

can some one tell me if there is a video on how to mount the power distribution block because these things are separated and it looks like there is a tray in the bottom am i missing a part?can i get a link to the instructional videos?

Re: Main Power Terminal Blocks?
 

Don't know about a video, but the drawing provided here is pretty good. The part at the bottom is called DIN Rail, and is commonly used to mount a wide variety of electrical components in industrial settings.

Re: Main Power Terminal Blocks?
 

Jay,
The Anderson connectors are rated for 50 amps but in our application, that should be OK. The electrical system with the wire size minimums, 50 amp connector, battery, and circuit breakers, is designed so that a 2.5 minute match should not raise the temperature of any component to the point of failure. If you look up a wire table for #6, you will see a similar pattern for allowable current. The wire tables are rating current or "ampacity" for the temperature rise of the wire inside a conduit (or in free air if you find a really good table) for continuos duty. 'Free air' being a higher current. Since you are heating the wire in only a few minutes, you were drawing some serious currents. This is why I suggest all teams borrow or buy a current probe or 'Amp-Clamp' to check the current on their robot. You may have a few seconds of peak currents while starting motors but current draw should smooth out to less than 100 amps while driving. Since all the wiring was hot, you were drawing very currents all the time. This could have been due to the design choices you made for speed/torque/efficiency on each motor or you could have had some binding in the drive train or simply high friction in the beraings due to weight. Teams should always check their performance against the design criteria to be sure they are running near design parameters.
A final note: The wire heating would also conduct to the main circuit breaker so that it's trip point would be far less than designed. Did you ever trip the main breaker?

Re: Main Power Terminal Blocks?
 

Mr. Skierkiewicz, I do not recall the 120 A breaker ever tripping last year, I guess we were cutting it really really close.

Seeing that much of our main power distribution equipment is rated for ~50+ Amps, would there be a noticeable advantage of upgrading some of that equipment to ratings of ~120+ Amps say in a pushing duel between two robots?

Re: Main Power Terminal Blocks?
 

There is very little you can change other than wire. If you think of this in real world terms, (and I am just guessing here) with the amount of heat generated by your robot last year, you would have been dropping a significant amount of voltage in the wiring that was getting hot. Assuming you cut little or no wire from the #6 connected to Anderson connectors and you added some additional #6 then you had a lot of series resistance. I use an easily understood term for this loss called the "wire foot". Each piece of wire has resistance that translates to a voltage drop just by current passing through it. A "wire foot" is 100 amps (approx stall current on drive motors) flowing through a #10 wire which drops about 1/10 of a volt per foot of wire. Since 1 foot of #6 is about 1/2 WF, and you were passing more than 200 amps through your #6, a quick calculation would be 2 (twice the standard current) x 0.5 WF x 6 ft of wire=0.6 volts in just the #6. Add in the other wiring and the internal resistance of the battery (11WF) and you should have been resetting the RC on a regular basis as the voltage would have easily been drooping to below the 8 volt cutout for the RC. (200 amps x 11WF=2.2 volts just in the internal resistance of the battery) By substituting #4, you would have dropped the loss in the primary wiring (battery, connector, main breaker and breaker panel) by half or 0.3 volts. You can easily pick up that much by cutting the #6 wire length in half. Remember, you have to account for all the wire, black and red in your calculations.

Re: Main Power Terminal Blocks?
 

Jay,

I agree completely with what Al has posted. You had some very serious problems in your 2006 robot for the wire to become "pudgy" after a 2 minute match. Melting insulation could cause a short circuit of your battery...

My team pushed the envelope on motor utilization in 2006. We won two regionals and Galileo division at the Nats. We burnt out 4 sets of FP motors and quite a few drive train components doing it. We used 4 small CIMs, 2 FPs, 2 large CIMs and an air compressor. Almost all were running full power and/or full speed during the majority of time in our matches... We sucked so much current from the 12V battery that the "low battery" indicator on the OI would light up (even during practice matches).

Only once did our 6 AWG wires get warm. Investigation revealed that a frame had "racked" to the point that turning that assembly by hand was impossible. We fixed the mechanical issue and the wire temps returned to normal.

By increasing the wire gauge, you are treating the symptom rather than the root cause and other components will start to fail (connectors, batteries, et cetera). Failure of these types of components can be "very interesting" (translate: scary).

You might also consider that some protective devices, like the 120A CB, may have failed closed (contacts welded shut) on your robot to allow such high wire temps to occur without tripping.

As a mentor, I would have a hard time allowing my students to operate a robot with the conditions you describe. I would very likely take the unpopular position and force my team to withdraw from the competition if the root cause could not be determined and corrected.

Let me put it another way. If the main power wires coming into my house were hot and "pudgy", I could not and would not sleep in that house.

I strongly suggest that you follow Al's advise. Get a good clamp-on DC amp meter and compare motor measurements to design specifications.

Even though it is not against the rules, in no way would I endorse going to 4 AWG wire...

Regards,

Mike

Re: Main Power Terminal Blocks?
 

Ok,
So I checked the Rockwell site for the terminal blocks supplied in the kit this year. The are listed for accepting wires from #14-#6 and are rated for 75 amps each. The spec sheet says you can double up on some guage wires (not #6) but must derate the current handling. For our purposes with the 120 amp circuit breaker, 50 amp Anderson connector and 40 amp branch circuit breakers, this seems like an good product for our use (other then weight and size). I was unable to find a spec on current handling for the jumper though. If anyone can find it I would appreciate a post on the subject.

Re: Main Power Terminal Blocks?
 

I think that's the main reason they've added this requirement. In essence, the main goal of good wiring is being able to edit it efficiently. Anyone going from FIRST to small scale electronics will want to be very familiar with efficient power bus use. And being able to find all connections to main power helps a lot while you're staring at a big jumble of wires (depending on how good your wiring is >_>).