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Discussion Starter · #1 ·
I'm going to be running a K11-250, series wound. The motor has terminals to allow series or parallel wiring. Below you can see the poles connected for series and are not positioned to easily make buss bars. FYI - those wires were only used for 24V no-load brush run-in and controller testing.

I thought I could just move the terminals and build bus bars shown in red - much easier to do. However, when I disassembled the motor, I found the field windings connected to the terminals with a crimped brass fitting. This does not seem like a connection that will hold up to 1000A bursts and continuous road vibration.

Anyone have thoughts on this? Should I be brazing these connections? The wires are very short so there is not much room to work with the ends. I would hate to break something while trying to fix it when it wasn't originally broken :rolleyes:

Thanks for any input/comments!
 

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I would hate to break something while trying to fix it when it wasn't originally broken :rolleyes:
Why mess with it then? Kostov has a pretty good reputation as a quality motor builder. Chances are that the terminals are sufficient and consistent with robustness of the rest of the motor. I have never heard of a failure on a Kostov motor terminal. You may to do more harm than good. And if you alter it and have a problem there is little recourse. Should a problem occur with original equipment, Kostov is likely to help you. Just my opinions ;)
 

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Discussion Starter · #3 ·
Thanks Major - just wanted to verify there wasn't some kind of drastic design oversight here. Not a whole lot of info on the terminal configurations that I could find. And after the problems I ran into regarding the RPM triggers (finger tight and coming loose), I wanted to be sure.

I'll swap the two terminals and make my bus bars. All good :)
 

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Hi,

This is not a "crimped brass fitting".
It is a brass bolt with a slot, then the copper wire is resistance welded to it. As Major hinted, there are many other spots that would melt much before the terminals cause problems in case of overload :)
Of course have in mind that while motor may survive a single 1000A overload, it will probably not survive several overloads in a row. Also consider that thermal protection usually does not react on time to save you from too much time at 1000A...
 

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Discussion Starter · #6 ·
Hi,

This is not a "crimped brass fitting".
It is a brass bolt with a slot, then the copper wire is resistance welded to it. As Major hinted, there are many other spots that would melt much before the terminals cause problems in case of overload :)
Of course have in mind that while motor may survive a single 1000A overload, it will probably not survive several overloads in a row. Also consider that thermal protection usually does not react on time to save you from too much time at 1000A...

Thank you Plamenator! I couldn't see any indication of a spot-weld, but resistance welding makes perfect sense now - my bad :eek:

I was planning on setting up my Soliton1 similar to guys with the 11" Warps. So 1000A peak is not good --- what would you recommend as a motor max current? I won't be racing, but am looking for similar performance to the stock ICE. Which was in the range of 200 ft-lb (340 N-m). Based on the series-wound chart at 248V, I would extrapolate to somewhere near 700A. Would you agree? And (more importantly) is it advisable?


That was a good idea.
Thanks steelneck, I see no other way of easily connecting them in series without the risk of shorting the terminals. How have others done this???
 

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Discussion Starter · #7 ·
Can anyone recommend the max operating current for a K11-250? Is anyone running one in their daily driver?

... in the range of 200 ft-lb (340 N-m). Based on the series-wound chart at 248V, I would extrapolate to somewhere near 700A. Would you agree? And (more importantly) is it advisable?
 

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FWIW: On my K11-192 I ran about 100 hp. So at 170 volts battery sag, something like 450 amps for 2000 miles. New volt pack let's me run at 150 hp, but haven't pulled monster hill on way to work yet, sorting out recharge issues. At 3500 rpm motor is not hot to touch in summer desert heat. YMMV.
 

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So you hold it at 450 amps for climbing hills? That's about what mine does climbing interstate hills in my area at 75-80, pulling 75kw at 162V. That's what I was doing last time I blew an armature. I was running around 75-80mph for about 10 miles, probably 6-7 minutes but only hit that many amps going up hill.

What is your your maximum motor current setting? How often have you taken this motor above 500A? Ever hit 1000A?

I did it a few times with the ADC9. I think current wise it wasn't a problem. No commutator damage. When it lets go, it seems as though a winding has broken loose from the commutator bars somewhere. I believe it's a torque twisting thus mechanical issue due to the massive current and torque generated.
 

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No, 450 ish amps pulling monster hill @50 mph 3500 rpm about 4 minutes. Sol1 setting at 150 kW motor max. Don't think I ever went over 600 motor amps. FLA pack wouldn't output that much at that point in trip. My typicals are about 250/275 @ 60mph, however need to run logger again with new pack as I think overall power went way up.
 

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1500 miles+/-. Factory brushes which reminds me I need to look at. I try to keep it within the kostov chart for duty cycles. Ie: 250 amps = 100% duty cycle
 

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Discussion Starter · #14 ·
No, 450 ish amps pulling monster hill @50 mph 3500 rpm about 4 minutes.
WOW is right - what kind of temperature were you at after that sustained power draw?

Right now I've set up my motor at 220V and 500A. No problem pulling that in a 2nd gear flat road acceleration - and sustaining it through the start of 3rd gear. Only about 60 km/h. Maybe 4 seconds? I have not yet had my car on the freeway to test higher speed power draw. And I don't have my thermister hooked up for data logging yet. After some short test drives, the motor was barely warm - I am running a forced air cooling fan (4" bilge blower) right now as well.

Those settings produce some good acceleration, but not quite where I want to be - matching or exceeding the original ICE. I would need to crank it up to about 250V and 700A, but I'm not yet clear if this is safe/advisable???
 

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So how many miles on the Talon? I know you've had it running a while now. Just read your build thread last night. ;)

The ADC9 I had in my S10 had good torque at 500A, much better around 800 but I'm scared to allow this motor that much juice. As much as I love that takeoff power, I really want to just drive the thing and not smoke it!

Re the heat buildup, motors like this with interpoles are supposed to run cooler than those that don't like the ADC9. Mine came with a blower but it appears to be a cheap blower.
 

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People have been asking this question for years, and the motor manufacturers generally dodge it. The blame is not entirely theirs, however, as this question is almost impossible to answer as it depends heavily on the environmental conditions, the past and future current vs. RPM vs. time conditions experienced by the motor, etc.

So let's start with one spec that is usually given for motors which is the S2-60, or "1 hour" rating, which is the current the motor can handle for 1 hour without any part - internal or external - exceeding the temperature rating of its insulation. For the Kostov K11-250, the S2-60 current is ~210A.

Theoretically, you can use an equation for energy, I²t, to determine acceptable current at other timescales, but the problem with this equation is that motors have much more complicated thermal characteristics than, say, a straight conductor in free air. What happens, essentially, is that I²t underestimates the current rating at timescales longer than 1 hour (it actually doesn't go much lower than the S2-60 rating) and progressively overestimates the current rating at timescales shorter than 1 hour. In other words, you can't run a K11-250 at ~420A for 15 minutes, not without cooking the armature but good, and at 840A the brushes or commutator will give up the ghost long before the 3.75 minute mark.

So what max current is safe? Well, that depends on how close an eye you want to keep on your motor. In essence, you can trade security/convenience for performance. My suggestions, which I do not warrant and will not be responsible for their application, are to set max motor current to 600A if you don't want to worry too much about your K11-250. You can bump that up to 700A if you want a bit more performance and have the discipline to limit time at that current to no more than 15-20 seconds out of every minute or so (and running at the S2-60 current or less and at 2krpm or higher for the rest of the time). Only if you actively monitor motor current should you run at higher than 750A and I strongly suggest installing an optical thermometer aimed at one of the brushes as well.
 

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There was a thread about the K11 Alpha where planetmotor from Kostov gave some good information about the Amp time tolerances for the Alpha at higher Amp levels. I'm sorry I don't have a specific thread link but my tablet and the forum search feature were not playing well together. If someone else could find it it would be helpful to this thread.
 

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Discussion Starter · #19 · (Edited)
So what max current is safe? WellYou can bump that up to 700A if you want a bit more performance and have the discipline to limit time at that current to no more than 15-20 seconds out of every minute or so (and running at the S2-60 current or less and at 2krpm or higher for the rest of the time). Only if you actively monitor motor current should you run at higher than 750A and I strongly suggest installing an optical thermometer aimed at one of the brushes as well.
Thank you Tesseract for the detailed explanation. I will not hold you liable for any statements :)

The optical thermometer is a neat idea. I will investigate that further.
 

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Discussion Starter · #20 ·
So how many miles on the Talon? I know you've had it running a while now. Just read your build thread last night. ;)

The ADC9 I had in my S10 had good torque at 500A, much better around 800 but I'm scared to allow this motor that much juice. As much as I love that takeoff power, I really want to just drive the thing and not smoke it!

Re the heat buildup, motors like this with interpoles are supposed to run cooler than those that don't like the ADC9. Mine came with a blower but it appears to be a cheap blower.
Originally, I only "tested" about 15km before my Tsubaki taper lock failed. Then my EMW charger failed unexpectedly. I replaced the coupler with a Fenner and fixed the charger.

So I test drove about another 16km last night. Never got above 60km/h since I stuck to side roads that were not busy. Motor was fairly warm to the touch when I got home (lots of stop-starts at 500A).

Things seem to be running good so far (knock on wood)!
 
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