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[Music]
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[Music]
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we are now
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coming to the third chapter
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electric vehicle sub system design
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we can also call it a design of electric
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vehicle drive train because is primarily
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the drive train that we will drive
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design rest is common to a
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ice or a petrol vehicle
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so i start this by saying
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what are the common parts we actually
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did this in chapter one i am repeating
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it
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because now you have a better
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understanding of few things so what are
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the parts which are common between
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ev and a petrol vehicle ice vehicle
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body and frame well you can use body and
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frame of the existing cars
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of course the fact that you will have
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electric
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vehicle you have to look at the number
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of moving parts will be small
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vibrations due to the moving parts will
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be small
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can you change the material used for
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body
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well that's just something that work is
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just started
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and it is a future thing similar doors
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and power windows pretty much existing
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of course you will probably not have
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manual you will have all with motors
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and which requires electricity which
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a separate battery
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was used in a petrol vehicle today you
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do not need that separate vehicle
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battery you will take the existing
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battery
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convert it to the right voltage and
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drive all these
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more motors for windows and doors and
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things like that
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wheels pretty much the same except
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remember that if you do wheels with
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better material rolling resistance
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improves its significantly
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makes a difference to the car
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in fact the extra cost that you put in
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the wheel
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is more than recovered when you look at
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the cost
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reduced cost of the battery so i'll
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really spend time
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on making the wheels better suspension
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system again existing can be include
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included safety systems
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airbags parking sensors all those things
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will be similar
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except now you have to worry about
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battery safety
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well in early days as i told you you had
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to worry about petrol safety
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but now you have developed good tanks
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the way the petrol moves
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its well protected petrol getting
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lighted up
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and creating fire
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is unlikely so that the learning took
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place
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i don't know from when from early
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probably
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twenties nineteen twenties to all the
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time till seventy eighteen sixty seven
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nineteen sixty nineteen seventy
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where you do a similar learning
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electronic vehicle
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because battery per se has to be made
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safe and then current is being drawn out
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but you have to worry today you have to
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worry because if a battery catches fire
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it can be disastrous it has a lot of
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energy
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power steering system again
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similar except you know earlier you used
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to use hydraulic power
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steering system already in many cars it
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has been changed to
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electric there is no reason for us to
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use
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hydraulic will of course work with
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electric driven by
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not auxiliary battery but the current
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battery
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see in a petrol vehicle you also have a
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what is called dynamometer which
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converts the
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motion into electricity its called what
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dynamometer
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dynamo alternator or denim now you do
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not require that out here
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i should have told you that it goes away
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here
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directly use electric current
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similar thing with power braking system
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it is not going to be hydraulic
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it is going to be electric but as i
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pointed out
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many of the modern vehicles already have
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electric
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power steering electric power braking
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wipers and fluid pumps
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mirrors pretty much the existing meters
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measures can produce
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they can be electronically controlled
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new ones are electronically controlled
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manual mirrors interiors i do not see
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any major reason
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to change that interiors so these are
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the common parts
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what are the parts which leads to
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modification
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air conditioning system air conditioning
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systems again
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driven by hydraulic it is not driven by
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battery that auxiliary battery that it
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is there
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because actually consume a lot of energy
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so actually the petrol which is burning
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and driving the air conditioner here can
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directly be driven
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by electrically so you require motors
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motors for air conditioning systems
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pretty much the kind of things that are
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used in a
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home air conditioning system office air
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conditioning system
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cooling systems all kind of cooling
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systems which will require will have to
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cool the batteries will have to cool the
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motors and controllers
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and you will require these to be
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electrically driven
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rather than again petrol driven
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dashboard may need a few modification
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you have to add a few parameters
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and you can today make it more
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intelligent
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parts which can go away completely fuel
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tank will go away completely
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in fact battery comes instead of fuel
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tank engine and associated connections
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like sensors several of them they will
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go away
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clutch and transmission system should go
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away unless you make motor also
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which is requires multiple gear
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ecu and connections to other sensors
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again can be removed you may require
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something different for electric vehicle
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fuel pump and other engine subsystems
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will also go away
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there are things that are removed
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what are to be added most important is
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electric motor and controller high
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performance electric motor
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used for propulsion for movement
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controller which controls the motor
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transmission system
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require very limited amount of gear
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and yet you may require some
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transmissions gear is of course there
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single gear is absolutely required
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battery pack with bms that is a very
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important
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component all of them will have a can
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communication
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everything will be communicating to
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vehicle controller through can motor
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electric motor control battery pack
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everything will be communicating
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iot and telematics more or less
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everything has become electronics
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today communication is so common so this
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is something
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invariably gets added this is getting
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added in a conventional petrol vehicles
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also
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but today you can remotely monitor the
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motor controller the battery
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every single thing you can remotely
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monitor
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what's period is being driven how long
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it is driven at what speeds
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the various converters will require dc
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dc converter
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you may have a 350 volt battery
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or a 48 volt battery then you will need
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lights which are maybe 12 volt
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so you will require different dc dc
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converters
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a vehicle control unit sometime also
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called master control
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unit it will communicate with everything
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motor controller
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battery pack past some messages
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may communicate to the outside world
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can even get controlled a new parameter
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can get added
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very often certain parameters software
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parameters in motors
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controllers and in battery can be
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updated
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through a vcu you do not have to bring
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all these things to a factory
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to update the software you will
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invariably need now isolation circuits
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particularly you if you are going for
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350 volt and
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750 volt
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drivetrain because they are high voltage
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you do not want human being to ever
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touch that so you want isolation circuit
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which will isolate
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anything at that voltage to lower and
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lower voltage
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and the rest of the parts so safety
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becomes very important
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you require charger infrastructure now
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charging infrastructure is outside the
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vehicle
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not released like your petrol pump but
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there will be also on board charger
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i will talk about it what the difference
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is strictly speaking both things these
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things are not part of the vehicle
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but part of ev ecosystem
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you will require some drive software of
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course drive software a lot of it will
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be there
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in motor controller and in battery
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in the but there is a in vcu also
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certain software will be there
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could be there
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so you may have augmented safety systems
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those things may actually get added
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ok having done that let us recollect
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what we
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learned in chapter 2. we had learned in
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chapter 2
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that electric vehicle would need a motor
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and controller to drive a vehicle
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as per the drive train requirement i
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strictly speak not as per the drivetrain
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requirement
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as per whatever user wants
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but performance will be measured as per
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the drivetrain requirement
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so velocity and what i meant velocity
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and acceleration
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at least as per the drivetrain
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requirement probably higher
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what the drivetrain requirement does not
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give you is a torque requirement
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so it has to also meet the torque
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all the time we have learnt to compute
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torque so far we have not used it
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we did in one little bit when we talked
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about the truck
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say you require so much torque to
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to go up a slope to start on a slope so
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we did that so there is some
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thing that we learned in chapter 2.
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you also need a battery with sufficient
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energy
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to give you a vehicle with specific
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range
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otherwise you will have range anxiety
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but not just the energy battery should
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give you also sufficient power at every
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instant
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even as it gets older
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remember the vehicle ca the mo the
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battery capacity will go down
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your power cannot go down energy will go
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down
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power is important because power is
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linked to the force that you can give
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so very important
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we learn to compute what different
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vehicles require for a drive
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power energy and torque
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learn the impact of parameters like
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rolling resistance aerodynamic
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coefficient
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vehicle frontal area weight slope pickup
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acceleration regeneration
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now we will look at the design of
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electric vehicle
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i keep on mis missing that all this is a
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function of
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certain speed kilometer per hour
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or rpm that is also equally important
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so
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you can either call it kilometer
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per hour or rpm
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this is equally important
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let us look again little more deeper
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at torque speed and power
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if you remember we talked about torque
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large talk comes from two things one is
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acceleration
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and number two slope two things
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acceleration
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pickup time or acceleration
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and the slope both requires high torque
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okay maximum speed of the vehicle
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determines revolutions per minute or rpm
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of the vehicle
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and right gear ratio is to be chosen
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to optimize now the torque and speed
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this is not what
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we we did mention it didn't learn this
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and we also raised whether should we use
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a multiple gear or a single gear
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ev trend is single gear as far as
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possible
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we will talk more about it as we go on
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power requirement goes very high during
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high speeds
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somebody asked me belief was on the
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last gear you use very little power not
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so
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as the speed goes up power
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the last gear essentially basically
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means that
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velocity is not being reduced rpm is not
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being reduced significantly
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you do not require large torque at that
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time
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but you do require large power
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large gear last year will give you less
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torque
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therefore if you want to climb up you
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cannot use last gear
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okay anyway this gear last year first
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gear
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is all petrol engine
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so power requirement is very low at
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speeds less than 60 kilometer per hour
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and then it shoots up and i pointed out
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100 kilometer per hour 130 kilometer
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150 kilometer it can become very large
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because it is going
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cube of the velocity so from 60 if i go
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to 120
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my power requirement goes up by 8 times
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if i go to 180 kilometer per hour from
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60
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it will go by 27 times
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and corresponding energy requirement
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will go up
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what will you learn in this chapter what
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are the ev subsystems
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define what is called drive trade and
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its components
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and determine the performance
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of the key subsystems especially motor
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and controller
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and impact on the performance of
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electric vehicle
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and what are the vehicle specification
00:16:07
which will impact the drive train
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specifications and
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finally what are the battery
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specifications
00:16:13
i didn't write what are the battery
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specifications
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what are the other subsystems that other
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than drivetrain drive train is a major
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subsystems
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and do they impact the design of the
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drive train i have to take that into
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account
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having done this introduction let us
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look at the ev subsystems
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and remember right in the beginning i am
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leaving asides
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body tire suspension system
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doors and windows wipers again
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i am very fond of the snakes
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mirrors interiors
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if you leave aside this e v consists of
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first a drive train
00:17:14
this is the drive train
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sometime battery is included in the
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drivetrain strictly spring battery
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is connected to the drive then it is
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outside a drivetrain
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ev battery various dc dc
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converters an auxiliary and control unit
00:17:34
air conditioning system your
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things like power brakes
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power steering your lights
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all kinds of lights
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all these are auxiliary and drive
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control
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in fact even this even your opening of
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doors nowadays
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electrically you open the that is also
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accelerating control systems
00:18:05
so it is primarily a drive trade and ev
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battery these are the two
00:18:10
most important thing then there is a
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dc-dc converter this basically a
00:18:13
converters
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so that the voltages you can get an
00:18:16
auxiliary control unit
00:18:18
so essentially power is required by
00:18:20
these three parameters drivetrain
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battery
00:18:22
and auxiliary control units
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the control units as i pointed out
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includes
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actually control the vcu lights
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headlights power bricks power steering
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air conditioners heaters
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other motors here i got my wiper right
00:18:40
window glass sensors is a variety of
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sensors
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whole lot of sensors are put
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what is the ev drivetrain
00:18:54
essentially motors controllers battery
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plus gears gears is a very much
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part of it
00:19:05
these elements will will drive the
00:19:08
performance of the vehicle
00:19:10
the auxiliary elements that converters
00:19:12
will not drive the performance the
00:19:13
performance of the vehicle
00:19:15
will be driven by motor controller
00:19:17
battery plus gears
00:19:23
so vehicle performance how do you
00:19:24
characterize the vehicle performance
00:19:27
vehicle performance is characterized by
00:19:30
vehicle torque
00:19:32
vehicle speed vehicle power these three
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are you getting sufficient torque at the
00:19:40
speed that you want
00:19:42
and the power that you require
00:19:46
these are three most important
00:19:49
parameters
00:19:50
and for all of them there is a term
00:19:54
used continuous and peak
00:19:57
so you talk about continuous torque and
00:20:00
peak torque continuous power
00:20:01
and peak power particularly for power
00:20:06
why are you using continuous and peak
00:20:09
peak is for a short time 10 second 20
00:20:12
seconds
00:20:14
and primary difference between peak and
00:20:16
continuous
00:20:17
is the thermal design
00:20:22
for example a motor may have a certain
00:20:26
power in a continuous manner
00:20:29
for a short time you can go to higher
00:20:31
power when you go to higher power
00:20:33
your heat dissipation may be more so the
00:20:37
temperature will start rising if you
00:20:39
keep on
00:20:40
driving at higher power the
00:20:43
motor will become too hot and will fail
00:20:47
but 10 20 second let it heat up it will
00:20:49
cool down
00:20:51
so the primary difference between
00:20:53
nominal
00:20:54
ah and kanan will actually talk to you
00:20:57
more about it
00:20:59
and the peak is the thermal equilibrium
00:21:04
the heat dissipation
00:21:07
you have to design to have heat
00:21:10
dissipation for normal
00:21:13
for peak
00:21:17
your objective is during normal
00:21:21
temperature will not go up it will reach
00:21:22
a certain state
00:21:24
maximum number and it will stay there
00:21:27
peak it can go up slightly
00:21:28
and it will go down because this peaks
00:21:30
are always short
00:21:32
so this you must understand this is the
00:21:34
really i don't think any difference is
00:21:36
there
00:21:37
other than thermal well in the motors
00:21:39
and controllers in battery there is a
00:21:40
difference
00:21:42
battery high peak again
00:21:45
it has a impact on the life of the
00:21:47
battery but
00:21:49
normally you can do this
00:21:52
remember something that i had done it
00:21:54
and i'll
00:21:55
again talk about torque is force into
00:21:58
the radius of the tower
00:22:00
would come from the motor nominal talk
00:22:03
and peak talk peak talk for a few
00:22:04
seconds
00:22:08
peak torque is normally required if you
00:22:10
suddenly have to go for a
00:22:12
big slope suddenly for a short period of
00:22:16
time
00:22:18
you go to that and then come down
00:22:20
similarly peak torque may be required
00:22:21
if you want to suddenly accelerate you
00:22:23
have you are actually behind a vehicle
00:22:25
and you suddenly accelerate to go ahead
00:22:28
very short time
00:22:29
it is not a sustained organ
00:22:33
ok this vehicle speed i had done this
00:22:38
it is a cruising speed and peak speed
00:22:43
peak speed again for a short period of
00:22:45
time
00:22:47
10 20 seconds
00:22:50
cruising speed can be there all the time
00:22:54
this will be defined by motor
00:22:57
revolutions per minute rpm
00:22:59
is used and please
00:23:02
look at this very important speed
00:23:07
should be defined in meter per second
00:23:09
but most of the time it is defined in
00:23:11
terms of rpm
00:23:12
revolutions per minute huh
00:23:15
of course speed can be defined in terms
00:23:17
of kilometer per hour
00:23:18
you often talk about vehicle speed in
00:23:20
kilometer per hour kilometer per hour
00:23:22
if you convert kilometer per hour it is
00:23:25
three
00:23:27
kilometer per hour speed divided by
00:23:28
three point six because kilometer is
00:23:30
thousand
00:23:31
hour is three thousand six hundred
00:23:33
second so
00:23:34
thousand by 3600 seconds
00:23:39
is kilometer per hour divided by 3.6
00:23:43
and that's a meter per second if you
00:23:46
want to compute that
00:23:48
as in rpm
00:23:51
rpm into 2 pi
00:23:55
into r 2 pi r but it is a
00:23:59
revolution per minute so convert it to
00:24:01
second
00:24:02
is divide by 60 this is the rps
00:24:05
or not rps this is the speed in meters
00:24:08
per second
00:24:09
speed in meters per second is rpm
00:24:12
multiplied by
00:24:13
2 pi r divided by 60 and if i take 2 pi
00:24:16
by
00:24:17
r and look at it it is actually r p m
00:24:20
into r tie
00:24:21
divided by 9.55 so this 9.55 number
00:24:25
comes very often
00:24:26
keep that in mind most of the time it is
00:24:28
approximated as 10
00:24:30
you multiply it
00:24:33
rpm with our radius of the tower divided
00:24:36
by 10
00:24:36
you get meter per second
00:24:40
so if you have 60 if you have
00:24:45
3000 rpm
00:24:48
your tire radius is 0.2
00:24:51
so you get 600 divided by 10
00:24:54
60 meter per second or 60 divided by 3.6
00:25:04
or 60 multiplied by 3.6 to get you in
00:25:07
kilometer per hour
00:25:12
so speed is 3.6 into rpm
00:25:16
into r tire divided by 10 this is
00:25:18
something that you should use
00:25:20
and should be able to convert that all
00:25:22
the time i am going to give you an
00:25:24
assignment
00:25:24
without gear and of course after that
00:25:26
you have to take the year into account
00:25:29
similarly power in watts how is power
00:25:32
between what is defined
00:25:33
nominal power at peak power i remember
00:25:35
for 10 seconds it is force into velocity
00:25:40
which is same as torque by for the force
00:25:43
is torque divided by
00:25:44
radius of the tower into a velocity in
00:25:47
meter per second is rpm
00:25:49
into r tire by 9.55 you see
00:25:52
in here it comes division by r tire here
00:25:55
it comes multiplication by r
00:25:57
so r tire does not matter you can
00:26:00
actually write
00:26:01
this as torque into rpm by 9.55 this is
00:26:05
another very simple
00:26:06
important thing you know the torque and
00:26:08
you know the rpm you know your
00:26:10
power consumption
00:26:13
so if you have a 3000 rpm and torque is
00:26:16
20 newton
00:26:19
meter 3000 into 20 divided by
00:26:23
9.55 it gives you 6000 watts 6 kilowatts
00:26:29
very simple these two you must remember
00:26:32
and conversion
00:26:33
rpm to meter per second to kilometer per
00:26:36
hour power in watts
00:26:40
to torque into rpm by 10
00:26:43
you must remember this this something
00:26:45
that you will use it again and again
00:26:47
and i am giving you an assignment assume
00:26:50
vehicle radius radiuses 0.3 meter
00:26:52
convert speeds of 1000 rpm into
00:26:55
kilometer per hour and meter per second
00:26:57
and 2 meter per second into kilometer
00:26:59
per hour under rpm
00:27:01
and 80 kilometer per hour into meter per
00:27:03
second in rpm
00:27:07
all right do this as an assignment
00:27:14
the next very important this is the
00:27:16
critical thing
00:27:19
so far we are not assumed gears
00:27:22
though i have been talking about gears
00:27:27
an ic engine does not give you enough
00:27:31
torque that a vehicle require
00:27:36
so you put a gear to multiply the torque
00:27:40
a gear just multiplies the torque
00:27:44
so vehicle torque becomes n times engine
00:27:47
torque where n is the gear ratio
00:27:52
now whenever you multiply torque
00:27:55
you will multiply torques you multiply
00:27:57
torque your
00:27:58
speed go rpm goes down rpm
00:28:02
goes down by a factor of n so the
00:28:05
vehicle rpm is engine rpm divided by n
00:28:08
and vehicle torque is n into engine
00:28:11
torque
00:28:13
if you have a single here of a n this is
00:28:15
what is used
00:28:16
if you are multiple gears as the gear
00:28:18
ratio changes
00:28:20
your
00:28:23
multiplication and division factor will
00:28:28
change
00:28:30
vehicle power is engine power so it is a
00:28:34
vehicle power and engine power there is
00:28:35
no difference
00:28:37
torque gets multiplied rpm gets reduced
00:28:41
by the same factor so the vehicle power
00:28:44
and engine power is same
00:28:47
you will see the same thing in electric
00:28:49
vehicle
00:28:54
the well there is always a gearbox
00:28:57
efficiency i have not taken into account
00:28:59
which i'll leave it to you to leave it
00:29:01
to motor people
00:29:03
evs normally use a single gear n is to
00:29:06
one
00:29:07
as a point was pointed out there is a
00:29:09
certain efficiency efficiency can be
00:29:11
98 percent so very close to one we
00:29:14
normally will assume one
00:29:15
unless it is required
00:29:19
if there are multiple gears the
00:29:20
efficiency gets worse
00:29:22
but then it is not as easy single gear
00:29:24
is kind of almost fully attached
00:29:26
you can get very high efficiency 0.99
00:29:30
close to that here also
00:29:33
vehicle torque is motor torque
00:29:36
multiplied by n
00:29:37
so if i am getting a certain motor
00:29:39
torque and i require more torque
00:29:41
well remember that vehicle torque and
00:29:44
requirement can go very high
00:29:46
remember in a truck we talked about 1700
00:29:49
newtons meter newton newton meter
00:29:54
now motor will not give you you have to
00:29:56
multiply by n
00:29:57
we even talked about 3000 or 3000
00:30:00
500 newton meter
00:30:04
you have to have a gear ratio of n
00:30:08
maybe n can be 10 12 14
00:30:11
and then your motor torque becomes more
00:30:14
reasonable
00:30:16
in a similar manner vehicle rpm
00:30:20
is motor rpm divided by n same thing
00:30:24
same thing that you see instead of
00:30:27
engine now we are talking about
00:30:28
motor thus motor torque can be
00:30:31
multiplied at the expense of motor rpm
00:30:34
this is an important factor that you
00:30:37
want to take
00:30:38
it is pretty much the same of course as
00:30:41
was pointed out that if gear has certain
00:30:43
efficiency
00:30:44
it is not one to the extent it is there
00:30:46
that much is a power loss
00:30:51
ok this is something i am just wondering
00:30:54
whether
00:30:55
power loss will come well power loss
00:30:57
will come
00:31:00
as square or no multiplied and this
00:31:03
there is a single power loss efficiency
00:31:07
efficiency speed as calculated
00:31:13
okay so this is something that we will
00:31:15
be using all the time
00:31:16
so in fact it helps us design motors
00:31:20
otherwise
00:31:21
motor torque will become very large
00:31:24
we actually are able to design motor
00:31:26
with higher speed
00:31:28
electric motor you learn when you design
00:31:32
particularly pmsm motor
00:31:35
how do you increase the speed of the
00:31:36
motor by simply increasing the frequency
00:31:43
as you increase the frequency the speed
00:31:47
increases
00:31:50
so that is possible you rotate it faster
00:31:56
that will that is
00:32:00
easier to do gettier torque is a tougher
00:32:03
job torque requires your
00:32:08
more current more magnetic
00:32:13
magnet has to be more powerful so it
00:32:15
becomes more difficult
00:32:18
anyway we will learn this but this is an
00:32:19
important thing that i actually wanted
00:32:21
to
00:32:22
model so a very important question comes
00:32:26
in electric vehicle do you use multiple
00:32:28
gear changeable gear
00:32:29
or a single gear
00:32:32
now i know early electric vehicles were
00:32:35
designed with multiple gears they are
00:32:36
more or less copying
00:32:38
the petrol vehicle
00:32:42
today the trend is to move
00:32:45
design a motor which can take the whole
00:32:47
range of speed
00:32:48
and the torque with the right gear ratio
00:32:51
and
00:32:52
not have multiple gear far more
00:32:54
efficient no clutch requirement
00:32:56
no changing gear makes things far more
00:32:58
efficient
00:33:00
you are not always able to do that
00:33:02
particularly like example if a heavy
00:33:04
truck is there and suddenly you say
00:33:05
well i also want it to climb 90 degrees
00:33:10
that's the kind of requirement these
00:33:11
people will come up with
00:33:14
you will then have to worry about gears
00:33:19
generally fixed gear in my own vehicle
00:33:22
there is its a fixed gear
00:33:25
but there is extra gear that i can use
00:33:28
for reversal of course you have to
00:33:31
turn the motor in reverse direction you
00:33:34
have to have indications
00:33:35
not gear but there is a extra gear that
00:33:39
is put in my vehicle
00:33:40
but thats it is if i redesign that
00:33:42
vehicle i wont put that
00:33:48
single bear will be preferred but
00:33:49
sometime vehicle requirement
00:33:52
forces you to but as motors become more
00:33:54
and more powerful you will see
00:33:56
single gear will actually come up i have
00:33:59
repeatedly pointed out
00:34:00
power does not change except the
00:34:01
efficiency factor is there to that
00:34:04
extent power will get law
00:34:06
lost will take that into account
