As we approach the summer solstice, I’m inspired to explore new and untapped areas of the realm of long boring technical videos. I think we’ve reached some sort of zenith this particular week.
The immediate object of this week’s video is another contest finalist, Alex Viera, who arrived to plead his case before EVTV viewers. Alex lives in Colorado Springs and is a musician with the U.S. Air Force – an oboe player no less. And he has a vision of populating the state with 4WD electric Suburus. He hopes to develop a conversion business by his retirement date in about 7 years. He seeks your vote in the “Build Your Dream” EV contest which is turning into quite a horserace. You can see the latest and vote here: http://www.projectooc.com/evtv/finalists.php
Mike Picard had jumped out to an early lead, but Brandon Hollinger has overtaken him. Brandon is another musician who did a superlative job of converting a Saab 96 to electric drive. He’s actually got quite a knack for garnering press attention to the concept of vehicle conversion. Time Video recently did a very interesting video piece on him which I thought was particularly well done.
I actually would have liked to include this in our next episode, but TIme being big ugly and stupid is of course impossible to even talk to about these things.
Back to big, ugly and stupid. The rest of our video this week is me attempting an explanation of the Netgain Warp 11 HV.
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Aside from the pernicious Alzheimer’s problem and my smoker’s cough, my onscreen personnae has another little problem that I simply deal with better in writing. That is a wide scope of audience. Some of our viewers DESIGN electric motors. Some of our viewers REALLY design electric motors at the highest and most modern levels. And some of our viewers still don’t quite get the Ohm’s law thing.
And we have everything in between. You don’t really need to be an electronics design engineer to VERY successfully build an excellent running and beautiful electric car. Ultimately, a motor is a motor is a motor and they have three or four connections with plenty of sample connection diagrams available. The basics are pretty simple = hook it up to a controller, press throttle pedal, and magically they convert battery capacity into forward motion. They are what makes you “go”.
But not all motors are created equal. And selecting the right type for any particular car is of course a design choice that has consequences and results in the final car. A greater understanding is always a good thing.
But I’m a little trapped between my vague understanding of how some of these things work, the unfortunate terminology engineers inevitable choose and generally choose poorly, and the understanding of a broader audience. In real time, I’m constantly groping for words that would avoid criticism from the learned for misuse or wrong use of terms, while actually communicating the concept to humanoids not of the priesthood.
Pity poor me – no. Actually that’s been the central issue of most of my adult life and I do it well enough, but more easily in writing with the luxury of review and revision than standing there actually doing it in front of a camera. It’s been good to me in many ways. The pathological inability of engineers to read, write, or speak in English has provided me a pretty nice career. I shouldn’t complain.
In selecting a motor for our Aptima Motors eCobra design, George Hamstra naturally enough thought one of his motors would serve admirably for the project. I demurred somewhat noting that we were doing his motor to death in the Cadillac Elescalade, and the Speedster Redux this year, and that I was looking for something a bit exotic and new to talk about. Of course, the exotic and new also seems to be actually unavailable most of the time, so I was spending a lot of time chasing down interesting things that had 16 week delivery times and huge price tags (EVO) or were really just web fantasies a long ways from any fruition as a product (Remy and a host of others). The web has so many pretty pictures of so many beautiful things, and such a thinly grained reality component as to hardware you can actually make show up in your driveway.
His main suggestion was the Netgain Warp 11HV. Now Netgain is most known for the very popular Warp 9 which we’ve used successfully twice. Dismissed by the cogniscetti as a “fork lift motor” these motors are actually quite durable, and capable of 200kw power levels for a tiny fraction of the cost of a more modern BLDC IPM motor. The Warp 9 is undoubtedly the most popular mount for electric vehicle conversions.
The Warp 11 is the same only bigger. So the 11HV has some magic dust to make it do voltages higher than the 170v limit we normally recommend on one of these horses. With the Hellwig brushes rather raising that to 200v, I guess I don’t get it.
The main advantage of the 11 inch, is a longer torque arm. For the same voltage and current, you’ll get more torque from an 11 inch than a 9 inch simply because the force of interaction of the fields happens an inch further from the shaft – more leverage so to speak.
I had heard that the 11HV actually used the rotor out of a Warp 9 – giving up that advantage rather. So I was underwhelmed. A Warp11 without the advantage of the Warp 11, but could do a few volts higher?
Not precisely. And therein lies a tale. This Warp 11HV has about as much to do with a Warp 9 or Warp 11 as it does with a cake mixer motor. George’s preoccupation with the “Warp brand” has led him down a path where I think most of the universe misses the part about this being a COMPLETELY DIFFERENT MOTOR in all respects. Naming it a Warp 11HV confuses the issue. Painting it red doesn’t help.
And in truth, George is kind of careful about his product reputation. He notes a 0.004 return rate on his products and he’s justifiably proud of that. The 11HV is kind of a new and somewhat avante guarde design in his line. And he’s watching the few installations out there kind of carefully before promoting the motor widely. So it’s kind of not been precisely a SECRET, but not exactly pushed on the marketing front either until they see how it does.
And subsequent to his suggestion and after talking with several who have actually used them, in the words of EVBlue’s Wayne Alexander, it seems this motor causes a car to “go like a scalded dog.” Not intimate with deep Kansas vernacular, I’m assuming this means “with all due haste appropriate.”
The motor actually harkens back to an older General Electric design using interpoles to ameliorate the armature reaction and thus reduce arcing at higher voltages – in turn allowing the use of higher voltages at load and so higher power without damage. To study up on that, I returned to the Hawkins Electrical Guide.
Nehemia Hawkins was something of an icon to technical writers. He established a publishing empire on the basic premise of explaining the principles of electricity and its applications. Most know of him through the Audel’s series of guidebooks such as the Audel’s Radiomen’s Guide of 1934. But he did do a 10 volume opus under his own name in 1917. Today, you can look far and wide for a description of inductors, motors, alternators, and so forth before you find one with an illustration that does not look a little archaic. They were all stolen from this heavily illustrated encyclopedia. No one has really ever bothered to do better graphics on these mature topics. And so you see the same black ink sketch of a dynamo over and over.
Hawkins Electrical Guide – Volume I – Electricity and Its Applications is available for download from Google books and of course has been in the public domain for many years. Google has made a copy of this available in PDF format and in an utterly BIZARRE take on copyright law, claims some sort of vague right from the expense of scanning it and has made the incredible leap that they can then deny you any commercial use of it. The Internet just gets curioser and curioser. So don’t use it for anything useful, and for God’s sake don’t change the watermark or Google will do something….they were a little vague as to what….
In any event, I highly recommend the tome for those seeking a deeper understanding.
To describe what the 11HV REALLY does, I had to start with the Universe and all things electric and work my way down to the basic question of what causes brush arcing and why Netgain has an “advance” of 12 degrees on the brushes as shipped from the factory.
The short answer is that the 11HV can do up to 288v because of its’ Interpoles. The bearings have a 14,000 rpm limitation and the commutator about 9000. And so in theory you can put 2000 amps into a motor at 288volts and make useful power up to 9000 rpm using existing off the shelf components. That’s about 576kw or 772HP input.
Now if you do that, you’re going to blow this motor up into several hundred very high velocity pieces. So do it at least 100 yards away from me. But it does mean you can do considerably higher power at higher rpms than you can with a Warp 11 or any other Warp motor from Netgain. You do lose about 10% torque at the very bottom, but gain all the way up. We’re hoping to peak in the 4000’s somewhere with this motor at 240v.
We were looking at Zilla controllers for this project. Rich Rudman of Manzanita Micro, being his usual charming self and still raging over the damage we’ve done to his BMS business, managed to talk me out of it. Ostensibly they are going to produce the Zilla. As there are still victims of the James Morrison fiasco who have paid for the LAST great Zilla partnership in Otmar’s ongoing search for a date to the prom, still without receiving their Zilla’s, I guess I’m a little gun shy. We’re just not going to deal with this controller. It just doesn’t exist. I’ve got two on the shelf but we’re just never going to use them because I cannot in good faith recommend you try to buy one. And frankly, the technology has marched on anyway with newer and better semiconductor components. By the time they get all that sorted out, it will largely be irrelevant with newer and stronger products readily available and at a fraction of the price.
Irony of ALL ironies, George Hamstra actually had done a deal with Otmar several years ago to produce the Zilla controller. He didn’t even know the deal was dead until Otmar posted a bizarre notice on his web site that it had “fallen through”. He never even bothered to call George and tell him it had fallen through and nobody knows yet why or how it had “fallen through.” The Zilla could have been in production for years…
Anyway, we’re still looking at controllers for the eCobra. Meanwhile, we received kind of a transmission template with our Tremec TKO-600 and the hole in the middle is an exact match for the bezel on the Netgain Warp 11HV. What an omen. The adapter becomes trivial. We just hand the template to our machinist along with the magic number – distance to the flywheel face, and we should have an adapter and coupler.
It will be interesting to see viewer reaction to my hour long treatise on this topic. I’ve cringed a few times in the past over our “watching paint dry” battery episodes and they have had more views than any other. Perhaps my sense of what makes good video is not as sharp as I think.
Or maybe they’re not watching for just my jokes and taste in exotic alcohols….Our thanks to Alex Viera for the excellent bottle of Stranahan’s Colorado Whisky.
Enjoy
Jack Rickard
Thanks for Hawkins link, downloaded it already. Have not read it yet so forgive my ignorance.
A COMMON understanding of the inner workings of electric motors and their associated batteries and controllers is sorely needed. You are helping in that regard.
I understand that the Warp11-HV has interpoles -per your video. Does that mean it is a separately excited dc motor? I am a little in the dark about the definition of:
1-Separately excited
Thanks JMS
Hey Jack,
fantastic show and tutorial.Thank you.
I am really looking forward to your experimenting with regen using the series Netgain. We need regen for brake assist more than for charging the battery. On a FWD car I think that it is a MUST HAVE especially when driving down a twisting hill.
In this kind of situation, using the brakes or coasting a turn is quite dangerous or at the very least unpleasant because of under-steer.
Lack of regen braking is the only feature that makes me go away from DC series brushed.
Another great show, Jack!
I think you should do a separate series of informative videos covering the important selection topics for your viewers. I am sure you have planned to cover these topics in the EVCCON schedule. Maybe they can be the videos for information.
I thoroughly enjoyed this video.
-Chris
Jack, if only Glenn Beck were this good with his white board. Seriously, great show. I watched every drop of that paint dry and even hit rewind a couple of times when I missed something.
Just to prove I’m a motor ignoramus, here’s a theory: why not add brushes at quadrants 2 and 4 that are simply shorted to each other. That would short and cancel any potential in the rotor bars before they hit the main brushes and won’t take any space (or power) in the stator.
To work around voltage sagging, why not run your pack at 50V over the motor’s limit and let the Soliton control the max voltage applied? The extra top voltage would account for voltage sag and ensure full power reaches the motor without exceeding it’s max voltage.
JR
Hi Jack, great whiteboard session. I got a bit of a preview during my visit, but this was the full monty, including reveal.
It only seems boring when you know the stuff already, but if you are finally getting to see the inside and having it explained like nowhere else on the interwebs; it becomes riveting!
The 11″ 250V from Kostov that I am using for the prototype speedboat has the interpoles too. I’ll be limiting Voltage to the motor at 240V from the soliton setup, but as we are running at 292 ish PackVoltage I should be able to pump the full 240kW into the motor regardless of sag. For how long is the question. Good thing it came with forced air cooling, thermistor and rpm sensor out-of-the-box, I hope this will give me fair warning before I melt her.
I thought I knew motor theory pretty well but I enjoyed the chalk-n-talk and learned a couple of things from it.
If you do end up using regen with a series wound motor I’ll be very interested to see how it behaves in a car: if I understand correctly, with no current through the armature there is none through the field, so you are relying on the residual magnetism in the stator to get the party started as you transition from motoring to regen.
Hey Jack,
Did you research the LA May convention EVS 26?
All the best,
Steve Lumpp
Thanks for show – it was very informative- felt like I was back at school.
Have been thinking about the battery selection for the eCobra. It might be worthwhile investigating alternative batteries than can put out 8-10C for 30 seconds. I think this would better suit the limits of the motor and [if chosen] Solition1
Doing some napkin maths – 75 180ah Calb = 43.2 kwh range and around 420 kg. Good for 5.5 * rated @20% sag = 198 kw peak
Which is 265 hp.
Consider a 3.2v 20ah hypothetical cell which does 8 * rated.
Make 16 * 19.2v 120ah pack (total 96 cells) gives ~37 kwh range and around 350 kg. If we calc this for 8 * rated @20% sag this gives 245 kw peak.
which is ~330 hp.
John:
So what happens if you simply apply a reverse current to the field? What comes out the armature?
Using a Soliton1 to limit a higher pack voltage has some merit.
As to batteries, you’re reading my mind but not my timeline nor checkbook.
I am moving my battery lab from the house to the shop with a new constant current load added and some new instrumentation we will be testing as well. I have 16 of the A123 MD1HD 20Ah prismatic cells ready to test.
I think it’s time to do some battery testing. Apparently watching paint dry works with some segment of this viewership.
Jack Rickard
Jack,
If you are willing to consider A123 cells for a racing setup, then I would ask you to seriously investigate using LiPo cells. Not the big Kokam cells but the RC cells which are rated at over 30C constant. They make these cells in 6Ah format, they do put out as advertised and will last long if you keep the C rate down and they are readily available. At 8C constant on a 30C cell you would expect 400 cycles. You would end up with a very competitive power to weight ratio.
Check out what they are doing in the cycle/moped world. The cycle life data that these guys are acquiring is interesting to say the least, and alarming is you own battery chemistry similar to A123’s…….in real life conditions, where you get the very high current spikes that will only register on a scope, RC LiPo cells seem to have a very competitive cycle life.
It’s a pity that A123 bought out Enerland just when they announced their large format cells. Enerland made the best Lipo’s, pioneering the tabs at each end like the high capacity GBS. But the Chinese LiPo’s are now even better at a fraction of the price.
Jack: you asked “So what happens if you simply apply a reverse current to the field? What comes out the armature?…”
My original question was based on the assumption that you might be attempting regen with the motor in a series configuration. If you imagine lifting off with a series motor, there is a point where the current through the motor (both field and armature ‘cos they are in series)falls to zero. If there is no residual magnetism, no current in the field windings means no magnetic field which means no generator effect, which means no current in the motor…. I’m curious as to what would happen in practice if you tried it.
From your question, I guess that you were assuming a sepex set up would be step 1, and regen step 2?
Oh and yes – watching paint dry on batteries is riveting. Seriously, some of the battery-centric shows you have no doubt found tedious and expensive have been amongst the most useful
No, there is no 1 and 2. Regen on this motor simply requires some external switching and a means of initiating that. We have no way to precisely modulate that with the accelerator for example. But we could do so with the brake signal, and it is even possible to build a circuit to vary the current in the field with brake pressure from a transducer.
It COULD be done. I’m not asserting we will do so. But if the interpoles can do a good job of moderating armature reaction, it is much more viable than it was with a simple advanced brush situation.
Jack Rickard
Kelly makes a controller with regen for series motors. Anyone know how well the regen works?
http://kellycontroller.com/hsr14701700a144vseries-with-regen-p-896.html
I found another site that has book seven in the Hawkins Electrical Guide series complete with illustrations.
http://www.meekmark.com/dp/Hawkins7/projectID421e9ab940c97.html
A little late for the cell tests?
Thanks for this Chris. Almost straight off on page 1550 it shows me how the US 220V three line mains operates without two websites confusing me.
One site telling me the two opposite wires are in phase and another site saying otherwise.
This makes Jacks Anti-“anti-islanding” circuit so simple to make.
Andrew
Mark,
From what I know, cells don’t truly accept a charge except when its prolonged. Some have claimed up to 5% recharge from regen in the right conditions.
I think this Kelly will only work regen on a series wound permanent magnet motor. It’s not a separately exited series wound controller. You can see it hasn’t enough connections for that.
Our driving tutors keep telling us we will lose control and explode into flames and have our children taken off us if we freewheel. Regen is useful to slow an EV from over speeding going downhill without resorting to continual braking. Thats it really.
Andyj,
It is the braking part that I like about regen as it replaces the ICE engine braking. Frankly I would rather dump the regen current in to a resistor than try to charge the batteries.
Re Kelly controller, It has four terminals like the sepex with the difference that they are all heavy gauge.How many more do you need? The installation circuit shows a series motor (no magnets).
Jack, regarding your DC/DC issues, I understand you run without a 12V battery, and I wonder if that’s causing your problems? I think a small AGM motorcycle battery would help take peak loads off the DC/DC, and a battery like that should last a long time always being charged and never being highly loaded. Initially I just used the starting battery that came with the car but I’m swapping it out for a small AGM.
Mark,
We are mostly singing from the same song sheet.
My mistake. I assumed a SePex controller would require more connectors.
Found myself working with a “Berlingo Electrique” this weekend. It’s SePex but its controller seems to have more connections than days of the week!
a sepex controller will have 4 heavy terminals:
2 for the battery
2 for the motor armature
there will be 2 smaller terminals for the motor field.
series wound permanent magnet motors are as rare as compound motors.
the kelly series DC motors really do do regen, but the control is a bit on off.
Andyj, It seems that both of us got the facts a bit skewed. The Kelly HSR (series) has B+ B- A & S. The HSE (sepex) has five connections including the two for the field.
According to the manual, the brake switch triggers the regen circuit and a 0 to 5V input is used to regulate. I guess one could use an in line hydraulic pressure sensor for this.
“…series wound permanent magnet motors are as rare as compound motors….”.
Can anyone point me at an example of a series wound permanent magnet motor? “Series wound” means that the field is effectively an electromagnet in series with the armature. A (brushed) “permanent magnet” motor uses permanent magnets for the field instead so there isn’t a field winding for the armature to be in series with?
Actually most permanent magnet motors have the magnets on the armature. An SPM style has them mounted on the surface and the currently popular Internal Permanent Magnet or IPM motor has them embedded in the armature.
The fields are more like an AC induction polyphase motor and electronically commutated.
Jack
I wonder how long it will take the EV industry to discover the benefits of yet another BLDC layout ie the Outrunner. By placing the magnets on the outside and having them rotate around the stator, you gain on the turning moment within the same package size, thus getting extra torque free of charge.
Yes Jack – absolutely – many are indeed BLDC. I was thinking of brushed PM DC motors like the Agni and questioning what a “series wound permanent magnet motor” might be
Why do I watch your videos? You’re the only person who understands how all this electric stuff, and electricity, works! If you’ve never seen paint dry, it could be interesting. All I know is that I found someone who can explain this shit!
Excellent lesson. Where do I pay?
http://store.evtv.me
just one correction (sorry I’m late),
I’ve examined the rotor design more carefully, and the segments form a ring, for lap or wave.
in your video @about 83:00 you state the loops are open ended. But they could not react with much of anything in that case, except eddy currents within the wire.
so half the segments are north, and half are south (or if you have 4 brushes/poles, 2/4 are north, 2/4 are south). But the rest of the segments/inductors help keep the current flowing in the same direction in the rotor, and same pole position relative to the stator, as individual segments get reversed.
At least that is my guess.