Understanding the Tesla Model S Performance Motor

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Hello, I am Professor John Kelly and this is the  WeberAuto youtube channel. Today I am excited   because we are going to go through a performance  motor from the rear of a Tesla Model S P90D   from the model year 2016. Now our school here,  our automotive program actually, has a 2018 P100D,   but they wouldn't let me disassemble  that one so I searched all over   tried to find a rear-drive unit which is the motor  the gearbox, the inverter, everything all together   and as you can see here in this photo. I finally  found one that we could afford. It is a burned-up   one, it was a from a car fire and I thought "Well  how hard can it be to just clean all that smoke   and soot off of there" and I will tell you it was  a mistake to buy. Never buy anything that's been   from a burned vehicle. We spent way too much  time trying to clean this thing up and of course,  

it has some damage to the electronics, but  I wasn't so concerned about that as I was   the gears and the some of the neat things  that I like to look at in my videos and so   let's get started looking at the pieces of the  performance rear motor on a Tesla Model S. I've   got the housing right here of the gearbox, one  half of the housing, the other half of the housing   is on the other side of the stator housing  back here on the other side of the bench, but   inside of this housing right here we have places  for three bearings to sit. We have places for   the three-phase cables from the stator to come  through, and then we have two coolant passages,   that we'll look at a little bit later, and it  and as a matter of fact I want to divide this   video into four separate sections. So section  one that we're doing right now is the gears and  

the motor, Section two will be some unique things  about these bearing,s they're pretty incredible.   Section three will be on lubrication,  these bearings require some special lube   in order to withstand the high rpm that  they operate or can operate at, and then   the fourth section will be on the cooling  system to keep that oil cool so that the   bearings will continue to survive along with the  rotor and the stator to keep everything cool.   As with any other transaxle transmission we have  to have a final drive gear, the differential unit,   so we have the differential case from this  P90D Model S. and the very first time I   split the case and got this thing apart, and  saw this gear sitting there sideways in this   gear reduction unit, some people call it a  transmission, it's a gear reduction unit,   it does not shift, it's a one-speed gear  reduction unit, but I started laughing   because this has the biggest bearings  I've ever seen on a differential   of a front-wheel-drive or rear-wheel-drive  transaxle style with the helical cut gears.   So this ring gear is monstrous, it's a  213-millimeter diameter ring gear and   it's 50 millimeters thick, that's incredible, and  it's held to the differential case with 16 bolts   which is pretty unusual. There are other cars,  front-wheel-drive cars, that vans and so on that  

also have 16 bolts holding that ring gear on  but they're not 50 millimeters thick either,   but the thing that really made me laugh was this  bearing back here. This bearing is 110 millimeters   in width and it's just a monster and so we'll  take a look at some of the specifications on   these bearings here in a little bit but a  differential is a differential this thing   operates just like any other open differential and the maximum, well let's see this differential  has 78 teeth on it, and the maximum rpm that this   differential rotates at the top speed of  this 2016 P90D Model S at 155 miles an hour   this is only spinning at 1841 RPM, so this  is the slowest spinning part in all of this   gear reduction unit, so by comparison  I've disassembled two other   EV or Electric Vehicle gear reducers, and I just  want to show you uh how they compare to the   Tesla performance model right here. Now I know  this is comparing apples and oranges because   this is a performance model and these other  two are not but this next one that I have   right here is from a Chevrolet Bolt EV and it  has, instead of 16 bolts holding the ring gear on,   it has 12. It has some decent sized bearings but  they're smaller than the Tesla one and  

look at the height difference in the ring  gear, it's only 34 millimeters thick   rather than 50 millimeters thick, and then  if we bring in the little Nissan Leaf,  it has eight bolts holding the ring gear on and  it only has a 32-millimeter wide ring gear right there. So I know these vehicles were not  made for performance and I'm not trying to   make fun of them or downplay them, I'm just showing  you how big this Tesla performance differential is   compared to other EVs on the market, and as  a matter of fact in any other front-wheel drive   or rear-wheel drive transaxle that's out there. Okay, here's a few other photos showing   the differences in the physical size  of these differentials and ring gears   now let's put this Model S differential  into the gear reduction unit housing with these big ball bearings. They just slide down into the housing but  it's a lot harder to do than it sounds,   so once that's fully seated we can move on  to the next gear which is our countershaft   and it has two gears on it it has the  pinion gear that drives this ring gear here,  and this pinion gear has 25 teeth, and  the ring gear has 78, and if you take the 78   teeth on the ring gear and divide it by  the 25 teeth on the counter driven gear   then we get a gear ratio of 3.12 between these  two gears, and then it also has a counter drive   gear that has the same 78 teeth that the ring  gear of the differential has except they're much   smaller, and they are driven by 25 teeth that  hooks to the motor shaft so let me set this counter gear down in now, take my sticker off just like that put my sticker on  the top here instead of the bottom.   Alright, at the top speed of the vehicle at  155 miles an hour or 250 kilometers per hour   this shaft spins at 5743 RPM which is  3.12 times faster than the differential  

by the way, the differential turns the same  speed as your rear tires so on our P100D   and on the P90Ds that I've researched, the rear  tires are a little bit taller than the front tires   and so it's just the rear tires that this differential will spin at the same speed as.   Okay so uh the next shaft that we have I don't  know the exact name I just call it the motor shaft   because this shaft connects directly  to the motor and it has 25 teeth on it   that drive the 78 teeth of the counter  drive gear so we get another 3.12 gear   reduction so I'm going to take this shaft now  the motor shaft and put it down in its bearing   just like that. Now these bearings on the  motor shaft have to handle the rotational  

speed of that motor shaft and of the motor  itself because they're all connected together   and we'll take a look at the motor here in just  a moment but I did the math for the tire size   that come came on the rear of that  2016 P90D, and at the 250 kilometers per   hour or 155 miles per hour this shaft in  these bearings is spinning at 17,919 RPM   it's almost so almost 18,000 RPM the motor  is spinning if you run your vehicle up to the   top speed, which of course you better  do on a track somewhere rather than   breaking the legal speed limit but those are some  incredible speeds. Now of course most people will   never get anywhere near those speeds but those  speeds require special lubrication pumping up the   special oil through these bearings to keep  them cool at the higher speeds, and special   cooling system to keep that oil cool. So anyway  now we've got, if I tip it up on its side here, we just have our motor shaft spinning the counter  drive gear spinning the counter driven gear   spinning our differential our  differential case and our tires   and that gives us an overall gear reduction  of 3.12 from here to here multiplied by 3.12   from this gear to the final drive which gives  us an overall gear ratio of 9.7334:1so   9.7344 rotations of  the electric motor to one rotation of the tire . 

All right now let's bring in the electric  motor. This motor weighs 27 and a half kilograms   just a little over 60 pounds which is  more than I'm able to just toss around and   so I'm going to set it in some "V" blocks made of  wood here to show you a few things about this   about this rotor. Okay uh the first thing is that  the P90D this the version of this rear-drive   unit was only from 2015 through 2016. the part  number of this rear-drive unit ends in the letter   Q and the part number of the rear-drive  unit in our 2018 P100dDends in the letter   R, so there's been one more revision somewhere  for the increased performance of the 100 kilowatt   hour battery, but I would imagine they're very  close to the same, maybe some differences in   bearings, so let's take a look at some  specifications here this is a three-phase   four-pole AC induction motor. This has no  permanent magnets in it, this is an induction motor.  

It is rated at 370 kilowatts or 503 horsepower  unless you put it in Ludicrous mode, in which   it goes up to 391 kilowatts or 532  horsepower. It has a peak torque of 469   pound-feet of torque or 636 newton meters, and that  is in Ludicrous mode I could not find any torque   specs for regular mode so if any of you know  what those are or if these numbers are incorrect   i've had to go back in the wayback machine on  the time machine on the internet to find some old   Tesla documents to get these specifications, i  didn't pull them off anybody else's website,   this is Tesla only specs that I found now as I  mentioned before we have a gear reduction from   the motor to the tires of 9.7344, I think I said 334 before   but this one is correct the 9.7344:1 and that's rotations  

of this rotor, it takes 9.7 of them to get one  rotation of your tires and as I said before also   this rotates up to 17,919 rpm at 250 kilometers  per hour. Now uh when I first heard that number   the 18,000 rpm, I thought, well I wonder what kind  of bearings that is using, because the later   Toyota Priuses have motors that spin up to 17,000  rpm at their top speed but their top speed is only   I forget it it's just barely over 100 miles  an hour I believe, and this goes up to one 155   and the new Model S that was just announced  goes up to 200 miles an hour, so I'm really curious   to see what they have for bearings, but so there's  some very unique things about these bearings.   There were some bearing failures early on on the  Model S and they switched to what everybody calls   a ceramic bearing, it is a ceramic,  it's called a silicon nitride according to SKF's   website. Now SKF is the bearing manufacturer  for the majority of the bearings in this   gear reduction unit and here  for the motor these bearings   the ball bearing portion of the bearings  are made of a non-conductive material   so if i turn this around here let's zoom in so you  can take a look at the balls in the ball bearing   see how they are not the shiny silver  typical ball bearing that you would see in any other bearing there's kind of  the dark color that is that silicon nitride   and both front and rear bearings  on this motor are non-conductive so   there's no electrical current that can run  through there no arcing that can occur and   damage the bearing like what happened on  some of the earlier models from what I read   the balls are 60 percent lighter than the previous  ones which means they have less mass and can spin   at higher rpm, they don't expand like steel  bearings do and so they can run at higher rpm   it takes a special lubricant. there's  a special seal that I've pried off

that goes on the outside so the seal is this  dark seal and this is the lubricant that's on the   the back side of it but normally that would be   right here covering up those ceramic balls so that  you couldn't see them, but I wanted to see them so   very interesting bearings these bearings have  no external lubrication fed to them, they have no   external cooling system fed to them, and this rotor  does not spin in oil transmission fluid coolant,   it's a dry spin inside of a sealed housing. Okay  as you can see the copper color here on the end   of this rotor, the rotor does have a copper core,  you can see some of the connector bars on either end   they appear to be just straight through without  being tilted or twisted on the front of the motor we have a speed sensor reluctor wheel right here this  two tooth ring, on an induction motor we just   need to monitor the rotational speed of the rotor  of the induction motor, not its actual relative   position, so just need to know the speed. Both  bearings, this one here and the one in the back   we just looked at, are the same part number from  SKF. I tried to find this bearing on their website   it is not there. Other bearings of the same  type are there but this part number is not   available on their website or in their catalog from what I could see. let's take this rotor and  

put it into the gear shaft now for the rotor and see the whole gear train put together. Okay that's   quite a chore putting that in there but as you can  see it just connects directly to that motor shaft   and as it rotates 9.7344 times we end up with one rotation of the   final drive unit itself that  hooks to our cv shafts cv half shafts. Here's the end of a cv half shaft the tripod or  tripod joint that just slides right into a side   gear and there's another one that comes in from  the other side, so as your electric motor turns   so so do your cv half shafts and your tires   all right so this is pretty basic stuff there's as  far as the gear train is concerned there's nothing   magical about this other than  it's just big and heavy duty   but as I mentioned before these bearings to  withstand the high rpm that they have to   at the maximum vehicle speed and even faster on  the newer ones have to be some special bearings   now I mentioned before that the Toyota Prius  MG1 and MG2 rotors on the latest generation   2016 and above can spin clear up to 17 000 rpm  but there are these little tiny lightweight   rotors compared to this thing, these  bearings have got to hold the big heavy rotor   and handle a whole bunch of torque at the  same time, so an interesting thing is that the   rotor itself is only supported by these two  little silicon nitride deep groove ball bearing,   non-conductive bearings, and that just  spins inside of the stator assembly   back here. Let's take a look  at the stator for a moment. We have a stator housing cover that fits right  here and we have a bearing, a non-locating bearing,   so it moves just slightly as the rotor heats up  and cools down, and then the locating bearing is   all the way in the bottom of the bore here.  The locating bearing is the one that holds solid  

it doesn't move with expansion and contraction  of the metals as they heat up and cool down.  This is a 60 segment stator assembly, it has 60 segments. I'm not sure how   many poles it has i'm not sure how  it's wound but if any of you know let me know because I couldn't find anything  anywhere as to how many poles it has, i know   the motor is a 4-pole. This stator assembly with  the housing that it's in weighs 125 pounds or   56.7 kilograms. This thing is heavy very heavy it's  not something you can just toss around easily   and especially if it has the rotor inside of it. On the other side of this stator  

housing if we turn it around we've got  the other half of the gearbox so our differential locating bearing that holds  solid and doesn't move is right here, our   countershaft locating bearing goes right here, and  our motor shaft locating bearing goes right here.   Now notice we've got an oil pump, there's an oil  pump pickup tube right here there's a magnet for   any metal particles in the special fluid in  this thing and then we've got kind of a windage   tray to keep the movement of the ring gear from  sloshing up the oil that's trying to be picked   up by the oil pump. So the oil pump has this 23  tooth driven gear right here and this is driven   off of that 78 tooth ring gear which means it's  overdriven by the ring gear about a little over   three times, so whatever ring gear speed is this  oil pump spins three times faster than that   and this oil pump has one job and it's not to  lubricate all these gears it's to keep those   bearings alive at high rpm, so if we look at the output of this pump it has this kind of a t-shaped   except with three outlets uh piece coming off of  it this piece right here that goes back into this   housing for the bearing feeds three evenly spaced  oil holes that go into the back of the bearing   and then force fluid through to the front  and that's on that motor shaft bearing and   then this tube right here sprays across to  the other bearing so our motor shaft has   two different bearings on it, and then the center  piece right here sprays on the motor drive gear   because this is the gear that's going to have all  that torque put to it, so the big deal here is that   the rotor of this motor spins on those  two little lightweight, non-lubricated,  non-externally lubricated, non-cooled ceramic  silicon nitride bearings, but it turns the motor   shaft and the motor shaft has to handle all of  the thrust torque from rotating and turning that   counter drive gear and the counter driven gear in  the end then that gear drives the ring gear.   So with what did we say um 636 newton meters  maximum, 469 pound-feet of torque, on the rear motor   here, that's a lot of torque, and these bearings  have to, they have to be very strong   to be able to handle that amount of torque, and  they require a lot of lubrication and this pump   as I mentioned only has one job and that's to keep  those two bearings lubricated on the motor shaft   and also to spray oil on the motor shaft drive  gear where it meshes with the counter-driven gear.   So that's pretty incredible when I first opened  this up and I saw that oil pump I thought oh   it's lubricating all these bearings and whatever  else, no it's just the motor shaft uh bearings and   the gear so when I looked up the part numbers  for the two bearings on that motor shaft have   to spin clear up to 18 000 rpm, I just wanted to  see what the specifications were on the bearings. 

Were these also a special silicon nitride bearing or not? and they're not, they're, it's a   special high-quality bearing, I think they call it  their Explorer Series bearing, but an interesting   thing in the table I found on these is that one  of these, well there are two speed ratings for each   bearing. There's one called a reference speed which  one of them is at 20,000 RPM, the other one is at   18,000, and then there's a Limiting Speed which is a mechanical limiting speed   without any doing anything extra, with  no external lubrication, or anything of   13,000 and 11,000 on those bearings,  but then I saw a little note that said you can run   bearings higher than those speeds if you do  some special things, so the catalog says it   is possible to operate a bearing at speeds above  its reference speed, its adjusted speed, or even its   limiting speed. So we're running these bearings  above the limiting speed, it says before doing   so make sure you do a thorough analysis and  take whatever further measures may be required   such as the use of special cage executions  or consider using high precision bearings.  

regarding management of the effects of increased speed consider the following options. So listen to   these options and let's see what how they compare  to what tesla did here control the resulting   increase in bearing temperature by additional  cooling so this pump here running fluid constantly   through these these two bearings uh gives it  the extra cooling compensate for any reduction   in bearing clearance resulting from increased  bearing temperature so the bearings get hot   and then the balls expand and we don't want them  binding and so the bearings that are in these   are special high clearance bearings there's a  clearance that's above the the regular bearing   and then there's two, three, four, five, other things  two of the most important ones in regard to the   Tesla motors are: Ensure that the lubricant  and lubrication method used are compatible   with the higher operating temperature of the  cage execution, so as i mentioned before it's a   special lubricant this isn't just gear oil, this  isn't just regular automatic transmission fluid,   Tou need to stick with the tesla  recommended oil for this and then check   that the re-lubrication interval is still  acceptable particularly for grease lubricated   bearings oil lubrication may be required and so  Tesla is using oil lubrication. so they've done   what they need to do to run these bearings at  higher speeds and of course you're not going   to be running at top speed all day long every day  and so it's probably not a huge concern for   most people but it's very interesting the  things that they have done in this gearbox.   All right now as far as lubrication I've mentioned  that takes a special lubrication I don't know what   it is i don't know where to get it other than at  a tesla service center so if any of you know what   it really is and don't just tell me it's Dexron -VI, I've read that I don't believe that at all (See corrections in video description)   let's share in the comments below what it is. All right now as far as draining   the oil from the gearbox, right here on  the bottom of the gearbox there's a drain plug   and right here on the side, there's an oil  fill and oil level check I assume but the Tesla service information that  I've accessed is less than helpful.   Alright on this housing let's take a  look at a few other things while we're here   there's a vent here on the gearbox  side and then there's a separate vent   for the inverter the power electronics portion of  that I mentioned that this drive unit is out of   a car that burned down but I was able to clean up  the tag enough that we could read the word Sport   right there and that's just like the  the tag in the P100D that we have   it also says Sport up here in in the part number  and description above that so this is the   the Sport version of the motor I  mentioned that vent for the gearbox this   drive unit has three different areas that are sealed off from each other. We have everything  

that's in the gearbox that we've looked at and it  has the special gear oil in it as we've discussed,   but that needs to be totally sealed from getting  into the inverter area where the electronics are,   it needs to be totally sealed from the anti-freeze  cooling passages that run through this drive unit   as well, and it needs to be sealed from getting in  where the rotor is because that's a dry area.   and so there's special seals and o-rings all  over the place to keep those separated and so   if you're planning on taking one of these apart  and then putting it back together to reuse it   you better keep all that in mind because one  leak of one especially any type of fluid into the   inverter area is going to cause some some major problems. okay well let's look at how this   drive unit is cooled. if we look at the back  cover of the stator assembly, if you look at this   photo of our P100D here on the hoist you can see that it has an inlet hose coming from the front of   the vehicle and I haven't traced where it comes or where it goes to in the front of the vehicle but   i'm sure it ends up at the chiller eventually  through some sort of a switching valve and   a radiator to get cooled down and then it comes back. We have this piece right here and that inlet hose connects right here now  since this is out of a burned up vehicle   the plastic inlet fitting melted off but this  is where the coolant would come into this drive   unit. Now as it comes into the drive unit it  goes two ways, one way is that it goes up  

and then all the way down the middle of this  hollow shaft right here and this hollow shaft with   a seal sticks down inside of this rotor assembly  the induction rotor now an induction rotor runs   hotter than the internal permanent magnet motors that a lot of other vehicle manufacturers use   so it runs coolant down through the center  of the rotor where it's blocked off at the   bottom and then it has to come back up around the outside of this tube where it goes through this   seal and then it goes up and out the top right  here and as it goes up and out of the top there   it connects to a pipe that we'll look at here in a moment. So that's one direction that coolant goes   from that fitting that you saw in  that photo the other direction is   it just goes down and through this fitting  right here which connects to this passage   which on the other side is just a straight  pass-through passage so you can see   you can see light through there and then that  feeds right here into the bottom of the stator   so the stator is cooled all the way around by  anti-freeze, a special antifreeze that tesla   wants you to use, so it comes in the bottom goes up and around, and then if we switch this around here   you can see that it comes out on the top right  here where it then goes through our gearbox   housing right here and down to feed and cool  the inverter IGBTs that run the three-phase   power to the stator assembly and we'll  take a look at those here in just a moment.   The next part of the cooling system is  that with if we put this cover back on here right there and we get our inlet and our rotor  cooler, oh by the way this other hole right here   is for the speed sensor for that toothed wheel  on the top of the rotor assembly, but what   i wanted you to see here is that as the coolant  leaves the rotor and comes up through that hole   there's a pipe right here and this pipe plugs into  that outlet coolant from the rotor and it comes up front here to a hole in the gearbox where it goes through right here and goes into the other half of the  gearbox so now we are ready to look at the cooling   passages in the other half of the gearbox .Oh  by the way, this wire right here coming out   by our three-phase connectors for the stator has four wires, two blue and two green. I believe these  

are stator temperature sensors, there's probably  an inlet and an outlet temperature I believe.   Okay, that pipe with a little hole that  went through the other half of the gearbox   lines up with this hole right here and  it comes through this coolant passage I've got labeled coolant flow going down, we've  got the coolant flow coming from the stator   going through and now let's look at the other side. Okay the coolant from the stator comes in   and goes through this passage right here  and it ends up on the inside of these three   sets of holes right here, so these three inside  holes are where the coolant from the stator comes.  now notice there's a temperature sensor right here  measuring the temperature of the coolant coming   from the stator, there are three sets of these  holes because they cool three sets of IGBTs,   capacitors, and other electronics, that are all  here to control the current and the voltage at the   three-phase connections at the stator assembly itself. Now I've taken this cooling   passage apart on this IGBT module, and as  you can see there are all kinds of little buttons,   whatever you want to call them, I don't know  how to describe them sticking up heat sinks   to transfer heat from the 32 IGBTs that are  on the other side here, and you can see this   definitely got burned up, into the coolant  as it comes through now if we compare this housing with the two the two fittings  here this housing is going to bolt   right there and so if the coolant comes in on the  inside one then that's this hole right here,   so that is going to come in and go up this  channel right here spread out to these four   holes and come up across all of those little  heat sink pins and then go back in and come out   on this hole right here which is the  outside hole on these four or three   cooling passages and once it goes  in to those outer ones you can see,   well you can see a cast channel where  the coolant comes in from the stator   then it cools all three sets of IGBT  modules and then it goes out through this   passage right here and there's an outlet  coolant temperature sensor right here also   and then it goes over and there's a hole right  here and notice there's a whole bunch more heat   sink pins right here on the gearbox side and  that little tiny hole that came from that pipe   back here on the stator housing feeds coolant into  this hole and then the coolant runs through all of   these little pins where there's a heat exchange  between the hot transmission oil and the coolant   so it transfers heat into the  coolant and there's a there's a plate   that fits right here that bolts down, you can  see in this photo here from the one in our car   what it looks like in the car, and  then it has this fitting right here   that bolts right there that is the outlet to go  back inside under the back seat to a water pump   where it's pumped through the onboard charging  module and then back out to go back   to the front of the car. So we've got the cooling  system for this the stator housing, we've got a   cooling system to cool the induction rotor, and  as I mentioned before they get a lot hotter   than internal permanent magnet rotors  because they have current running through   them where the permanent magnet ones do not. And then after the stator and the rotor are cooled

the stator fluid comes in and cools all the IGBT  modules and then goes out of the gear unit here   and then the coolant from cooling the rotor  comes in over here and helps cool the gear oil   and then it comes out this same fitting here  underneath the car to go up front to have the   heat removed from it or added to the passenger  compartment heat from what I have read and   understand but I have not physically traced that to verify that that's true. Okay so with all of these IGBT modules bolted up here  in the shape of a triangle as you can see here   in this photo, the last part to bring in would  be the inverter cover itself and so it bolts on right here and before I knew anything about  Tesla motors drive units I thought this   was another electric motor but even though it's  round like the stator assembly on the other side   it's not a motor it's just a cover  for the electronics that are in there.   Now on the front cover for this  inverter assembly cover we have two great big holes right here for the positive  and negative high voltage cables   from the high voltage battery underneath the  car so they come in and plugin right here   let's see this one is the battery positive  it's actually cast into the the cover and   this is battery negative and then there  was before it melted out a low voltage   black electrical connector there for  data communication, power ground, wake up   signals, and whatever else there may be, drive  accelerator position, and so on I'm sure other information sent to the inverter   to drive the vehicle. So this is the inverter cover.  Okay we've looked at a lot of stuff here on this   2016 Tesla Model S P90D rear drive unit I  believe it is very very similar to the P100D   in the 2017 and above and of  course the new released one that's   got the two individual rear motors is  totally different that has just been released   or announced. but I have, for this same 2016  Tesla, I have the front electric motor that  

we'll look at and it's different, I mean  it's similar but it's got some major differences   and then I've got all the power electronics,  everything all the high voltage cables all the   high voltage electrical components on the Tesla  Model S, we're going to lay it all out and show   you what's connected to what and how it works and then we'll do the same thing for model 3. I've   got a rear motor a front motor and the power electronics to go with that. If you've enjoyed   what you've seen here today and you feel like  donating to the Weber State University Automotive   Technology Department there's a link in the video description at the bottom, thank you for watching

2021-02-23

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