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Scott Drive 100kW AC motor & controller

174K views 441 replies 55 participants last post by  Hollie Maea 
#1 ·
efan said:
this controller+motor seem to be a new development, and I dont know of anyone who has used it..but it may be worth checking them out.

http://shop.greenstage.co.nz/product/100kw-scott-drive-ac-inverter-and-motor-package
Anybody actually seen or used this (new?) AC motor/controller combo? I see the Greenstage guys have a good history here, but this seems to be a first for them, and beats out the current HPEVS Curtis/AC50 combo by a good margin.

Thanks to efan for pointing this out!
 
#3 ·
...I see the Greenstage guys have a good history here, but this seems to be a first for them, and beats out the current HPEVS Curtis/AC50 combo by a good margin....
Hmm... interesting find. Always good to know what the potential competition is up to.

Note that this system uses a *trapezoidal* BLDC motor, not a sinusoidal type like, e.g., the Remy HVH250 motor. Without getting too wonky, the switching pattern needed for trapezoidal BLDC makes it impossible to use any type of field-oriented control algorithm - only 6-step "V/f" is allowed. This means poor low speed torque, and high levels of torque ripple, noise and vibration at all speeds. Here is a good overview of the two different types of BLDC motor.

As a result of these severe shortcomings, trapezoidal BLDC is really only suitable for small fans and servos, not traction applications.
 
#7 ·
Note that this system uses a *trapezoidal* BLDC motor, not a sinusoidal type like, e.g., the Remy HVH250 motor. Without getting too wonky, the switching pattern needed for trapezoidal BLDC makes it impossible to use any type of field-oriented control algorithm - only 6-step "V/f" is allowed. This means poor low speed torque, and high levels of torque ripple, noise and vibration at all speeds.
Great article, and makes sense -- it describes quite well what I see on my brushless e-bike as well :)

But... why not filter the discrete Hall signal into a sinusoidal curve? Or, if you've got a decent processor available, predict the true position of the rotor? At worst the motor is hooked to a flywheel, and at best to a 1+ ton car; the change in rotational velocity of the rotor should be relatively small during 60 degrees of rotation...
 
#4 ·
Great link Tesseract!

The only trapezoidally controlled brushless motors I've had experience with are little ebike hub motors. I guess the torque ripple explains why they growl so much under load? But I still don't grasp why they produce poor torque at low rpm, though I know from reading reports on Endless Sphere that this is a big limitation.

According to that link: "Sinusoidal commutation results in smoothness of control that is generally unachievable with trapezoidal commutation. However, while it is very effective at low motor speeds, it tends to fall apart at high motor speeds."
Can you put a rough figure on the upper rpm limit for sinusoidal control, or does that depend on the motor design as well?

Malcolm
 
#5 · (Edited)
Great link Tesseract!
Yeah, I thought so to when I read it. I've got all kinds of very expensive books on this stuff and none of them come close to explaining the basic difference in the two types of BLDC stator construction as well as that document.

The only trapezoidally controlled brushless motors I've had experience with are little ebike hub motors. I guess the torque ripple explains why they growl so much under load? But I still don't grasp why they produce poor torque at low rpm, though I know from reading reports on Endless Sphere that this is a big limitation.
Generally speaking, it's because there are only 6 points where the stator windings and rotor magnets are perfectly aligned in the trapezoidal BLDC; at every other rotor angle some of the phase current goes towards uselessly trying to counteract (or add to) the flux of the rotor magnets rather than moving the rotor through space.

According to that link: "Sinusoidal commutation results in smoothness of control that is generally unachievable with trapezoidal commutation. However, while it is very effective at low motor speeds, it tends to fall apart at high motor speeds."
Can you put a rough figure on the upper rpm limit for sinusoidal control, or does that depend on the motor design as well?...
The higher the rotor RPM the higher the stator frequency and therefore the higher the AC losses in the motor, thus the design of the stator sets a practical upper limit on the RPM, assuming the rotor can handle the centrifugal* force, that is. However, the higher the RPM the faster the processor in the controller needs to be to calculate the switching state needed to create the correct voltage vector for the rotor's actual position. In other words, at a high enough RPM the rotor will move a significant angular distance in the time it takes the processor to calculate the voltage vector. A graceful fallback is to drop the number of voltage vectors until you ultimately end up at 6-step operation.

* - the oldest argument on the interwebz is that centrifugal force doesn't exist, but everyone knows what it means so let's pretend that it does.
 
#17 ·
Umm.. not to give away any secrets, but the "Scott Drive" is actually a Chinese BLDC motor that I have been thinking of importing for use in my next build and to sell in the U.S. (since the U.S. does not produce a liquid-cooled BDLC motor).

Considering the crazy shipping from NZ and the extra middle-man, I am guessing folks would rather just have it shipped direct from China to the U.S. at significant savings.

I am currently "bargaining" with the factory over the price breakdown for bulk orders. If anyone is interested in joining a bulk "beta" order, let me know. I hesitate to put my name behind the product until I have fully tested it and it has "proven up".

Cheers
Can you share the information about this "Chinese BLDC motor"?

Very similar specs and measurements to these motors that have popped up on this forums for awhile now...http://en.glelec.com/cp.html (Shenzhen Greatland Electrics)


http://www.epowertransfer.com/UploadFiles/ehug.pdf
shows specs of the motors, much more info than the Shenzhen page..same products...
The specs on the "MP25L0" 30kw cont. 60kw peak (100kw for 10 sec?) 4000rpm max motor weighs 88kg again figures close to the 80kg listed for the Scott Drive.

An even more interesting model is the "MP20L0" 30kw cont. 50kw peak (90kw for 10 sec?) 9000rpm and only 68kg.
 
#20 ·
Hello,
The Glelec and epower are one in the same. Identified by the cooling ports being "in-line". They look very well made, but their torque-to-weight ratio is not as good as the Scott.

There are 2-3 other water-cooled BLDC motor cases floating around China. The "Scott" is different from the Glelec. Identified by the cooling ports being one at the top, one at the bottom coming off tangentially. About 4 companies "claim" to make this motor. A bit tricky figuring out who actually does. The advantage of the motor used by Scott is that if you dig deep enough you can find it rated for 540vdc (I'd still rather have 640v). This gives a LOT more torque from the same motor weight. That is the direction I am looking to go.

There is one other with the cooling port coming out in the middle like a belly button. But it is a bit small by American standards.

I don't want to go into too much detail since I am trying to bring these motors to market in the U.S., but I can say that I am now talking with the friendly folks in NZ at well. I see collaboration as the way to bring the prices down and get EV's into the mainstream.
What is your timeline on bringing them to the US market? I didn't see any update on your website.

I like the sound of bringing prices lower than the already shown 6,000$.
 
#23 ·
Just heard back from Philip at Greenstage about the Scott Controller. The controller is good for 150kW in a 30lb package which is pretty good when you consider that it comes with a contactor and precharge circuit internally. It can handle up to 450Vdc and 450Adc on the input and programmable on the AC output (not sure of the limits here). I was told that the price for a single controller will be $2945 which in my opinion is pretty amazing, because that is a lot less than a comparable Sevcon Size 8 or Tritium Wavesculptor 200 which are both over $6000, and can't do much more than 100kW peak. They both offer FOC control thou and work with Induction machines.

The controller at the moment uses trapezoidal control for BLDC motors and FOC/Sinusoidal control is in development and will be prioritized based on demand. Even if this software adds a bit of cost the controller is still ahead on cost based on all of the research I have done. I was also told that the full user manual will be completed shortly.

More Info here http://www.greenstage.co.nz/PDFs/Scott_Drive_100.pdf

Hopefully this information helps out!
Kyle
 
#24 ·
Just heard back from Philip at Greenstage about the Scott Controller. The controller is good for 150kW in a 30lb package which is pretty good when you consider that it comes with a contactor and precharge circuit internally. It can handle up to 450Vdc and 450Adc on the input and programmable on the AC output (not sure of the limits here). I was told that the price for a single controller will be $2945 which in my opinion is pretty amazing, because that is a lot less than a comparable Sevcon Size 8 or Tritium Wavesculptor 200 which are both over $6000, and can't do much more than 100kW peak. They both offer FOC control thou and work with Induction machines.

The controller at the moment uses trapezoidal control for BLDC motors and FOC/Sinusoidal control is in development and will be prioritized based on demand. Even if this software adds a bit of cost the controller is still ahead on cost based on all of the research I have done. I was also told that the full user manual will be completed shortly.

More Info here http://www.greenstage.co.nz/PDFs/Scott_Drive_100.pdf

Hopefully this information helps out!
Kyle
Did they happen to mention the controller RPM limit?
 
#26 ·
Switching frequency is not directly linked to maximum rpm speed the controller allows to produce for a certain motor. Switching speed usually factors higher than the produced fundamental frequencies output current.

See the manufacturers spec for the rpm limit on the controller.
 
#28 · (Edited)
Just got off the phone with Hagen Bruggemann of NZ who is using the Scott Drive. Turns out he ditched the transmission and is using it DIRECT DRIVE!! Nobody would consider this motor strong enough to do direct drive. Some even claim it should have weak torque. Obviously the skeptics are wrong.

He says no problem driving the RAV4 up steep mountains with full passengers and hang-gliders on the rack. USING DIRECT DRIVE??!

He can't really calculate efficiency on the flat because they cross a VERY steep pass every day and still average 250w/mile in a rav4.

He did mention that American brushed motors are a "joke" and "at least 10 years behind the rest of the world with pathetic efficiency".

Interesting and brilliant chap. He will be sending me some photos and more data. Stay tuned..
 
#38 ·
So how do those theorizing on paper that this system will suffer poor torque grapple with the reality of it's use in a direct-drive system heavily loaded in steep mountain terrain?....
I thought I made it perfectly clear that trapezoidal BLDC has poorer low speed torque and exhibits higher torque ripple compared to sinusoidal BLDC... You do realize that this is a comparison, not a statement of absolute fact, right?

In other words, if the Scott Drive system used a sinusoidal type BLDC motor then the inverter could use FOC to get even more torque and smoothness of operation from it.

But sure, I am just speculating based on essentially book knowledge about this stuff. You're the one putting your money on the line to import this system from China. I mean, maybe this is the exception to the rule, "if it seems too good to be true, it probably is"?
 
#39 · (Edited)
It doesn't seem 'too good to be true'. It just seems to work, and work well.

A Netgain 11" and Soliton are $6000 and known to be suffering premature failure (the net, not the sol). So the Scott doesn't seem like any more of a risky purchase.

The fact that the same brand of motors is powering full-size buses and the Scott system is able to lug heavy loads in the mountains using direct-drive is plenty of proof it works.

Are you aware of any Series DC powered full-size buses?

How about 176 lb motors doing direct drive with loads up steep mountains?

I am getting a Scott Drive system and will fully test it. Dyno it. The results (good or bad) will be made public.

Cheers :)
 
#40 · (Edited)
I deal with HEV buses all the time.
30-40 ft.
They have about 200KW electric with 200HP ICE.
having rode these with full passengers (30-40) up steep hills, they have to down shift to 1st gear.
Steep here is a slope with 30 feet incline in 100 foot of slope length. which is designated about 50% Grade.

So a 150KW seems way under powering a bus, especially direct drive. Now if the "Bus" is more like a 20 foot, with 10 passengers, might be closer.
 
#43 ·
I deal with HEV buses all the time.
So a 150KW seems way under powering a bus, especially direct drive. Now if the "Bus" is more like a 20 foot, with 10 passengers, might be closer.
Neat, I'd be interested in hearing more about the drive systems.

The buses use transmissions and the next larger BLDC motor rated at 1100NM and 240kw max @ 540dc. Sounds awesome till you realize it is 572lbs :eek: About the same as a V8. :eek:
 
#47 ·
Alot of trains also used brushed DC motors back before GTOs, Thyristors, and IGBTs were developed.

Just for the record, neither the bus or the SUV are actually direct drive, they have some reduction between the motor and the wheels. Whats more, the ratio on the bus I'd imagine must be something like 10:1 or more. You'd have to have a motor that outputs 5000 FTLBS of torque for it to really be direct drive
 
#48 ·
Well I certainly agree it isn't Direct-Direct, but 'direct drive' most commonly refers to direct AXLE drive and has the differential reduction as you point out. Usually this only compensates for the diameter of the tire. Bigger trucks have bigger tires and thus higher gear ratios. It would be intriguing to use a Columbia 2 speed axle or a farm truck 2-speed though. So far I haven't heard of it being done, but with the rodder crowd getting into EV's, it's only a matter of time...

I was asking if there was any buses using like a Soliton and a Warp 13 or something. Certainly seems possible, though I would suspect it would be one of those small 'airport shuttle' types and not a 'big' bus.

Trolleys move at about 5mph on train tracks, neat that they were electric, but that hardly counts as a "bus" drive-train.

So far nobody seems nearly as impressed that the RAV4 is direct (axle) drive. I think that is fairly impressive and suggests the system has some grunt.
 
#50 ·
No, full sized, conventional city buses with rubber tires. Here's an example: http://www.sfmta.com/cms/mfleet/trolley.htm


Note, this is not saying DC is the best motor or the wave of the future, but train and bus systems achieved decades of reliable service from brushed DC motors. Don't get me wrong, I'm rooting for your BLDC system!
ruckus said:
... Trolleys move at about 5mph on train tracks, neat that they were electric, but that hardly counts as a "bus" drive-train. ...
 
#52 ·
No, full sized, conventional city buses with rubber tires.
COOL! I didn't realize that. Thanks for the link. They say 275hp motor. Any idea what motor that is and if it is peak or continuous at that power? Interesting anyway.

Don't get me wrong, I'm rooting for your BLDC system!
sheesh, it's not 'my' system. I just want to test it and see if it's as good as it sounds or if I should build a 'fan' out of it... :D
 
#51 · (Edited)
I thought there was something in the rules about going around and filling threads about competitors products with negative and unsubstantiated posts. Maybe that's a rule in the future. Or just professional manners. Everybody sees what you are doing.

Here is your quote: "As a result of these severe shortcomings, trapezoidal BLDC is really only suitable for small fans and servos, not traction applications."

Hmmm... except it is working in a direct-drive setup and powering buses.

Bottom line: You provided zero DATA about the thread topic, only negative speculation about how your competitor's products are "unfit" for use.
 
#53 ·
If I am wrong, please Quote yourself in this thread about an exciting new drive system saying something positive.
He doesn't need to say anything positive about it if he doesn't want.

Here is your quote: "As a result of these severe shortcomings, trapezoidal BLDC is really only suitable for small fans and servos, not traction applications."

Hmmm... except it is working in a direct-drive setup and powering buses.
I guess that just shows your empty theories to be just that. Empty.
Speaking of which, do you have a source for the powering busses bit? Specifically what controller and motor they are using?

Bottom line: You provided zero DATA about the thread topic, only negative speculation about how your competitor's products are "unfit" for use.
He voiced accurate concerns about the Scott drive 100 (trapezoidal form for starters) and it was backed up with sources.

Note that you're launching personal attacks at Tesseract. He's done quite a bit of development work with this community, so people aren't going to take kindly to personal attacks on him
 
#55 ·
Rukus,
You accused everyone of "EV snobbery" because you got a low turnout on your 8" motor group buy, you accused everyone of burying their heads in the sand or falsely championing a worthless technology because they argue brushed motors can work fine in an EV, you accused an exceptionally well educated and experienced member with a long history of truthful posting on controllers of putting down a competitor and violating forum rules because he pointed out a possible negative in a controller/motor combo. To counter this massive asshattery you MAY have found a possible way to bring brushless motor and controller combos into the price range and size range that they make sense in an EV. Most everyone here LOVES the idea of more options in their price range, but they don't love someone who shits on everyone else's fairly educated opinions based on chinese data sheets and dreams.
 
#56 · (Edited)
Hello,

I have no favorite technology. I have no investment in a particular technology (unlike others here). It would be rather easy for me to spec netgain/soliton products for my conversions and be done with it. I merely want a system that is functional and reliable that will empower many more to build EV's. I am willing to test any available tech that I can afford. I have tested a brushed system and found it lacking. I am moving on to other technologies.

Cheers :)
 
#58 ·
The HPEVS systems sell kits based on the fact that they are not brushed DC and that they are something different, backed up by personal experiences documented on the forum. It sure as hell isn't the power:cost ratio!

The Scott Drive 100kw system for 6000$ will sell and sell well if you are transparent and open about the results of your testing. Let the performance of your product do the talking.
 
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