Hello everyone and welcome!
In this video we'll be discussing the question "Is it possible to tune an electric car for more power? In a similar manner to how
you can tune an internal combustion engine for more power." This is the third of a five part series
where i've partnered with Formula E to talk about the engineering behind electric cars. Now internal combustion engines generally require a spark
compression air and fuel. By adding more air and fuel you can generally extract more power out of that engine. In a similar fashion
electric motors require current and a magnetic force
the stronger the magnets used or the more electric power supplied and you can increase the power of the motor let's look at a simplified
explanation of a three-phase
permanent-magnet AC motor it's really comprised of two main parts the stator which has copper coils and is
stationary and the rotor which has magnets on it and rotates in order to force the rotor to rotate
the stator has three sets of magnets though in reality It could be many more
The magnetic force for each magnet is created by a wound copper coil
if you pass current through a copper coil it creates a magnetic field
with a north and south pole based on which direction the current is passing through the copper wires
these six magnets make up our stator which remain stationary in the center we have Our rotor in this case a
simplified rotor which is simply a magnet that rotates about its center with a north and south pole. As you pass a current through the
copper wires supplied from the electric cars battery that current creates a magnetic field in a pair of
electromagnets the north pole of the magnet in the center is attracted to the south pole of the top
electromagnet and the south pole of the magnet is attracted to the north pole of the other
electromagnet similarly the north and south poles of a separate winding will repel the magnetic rotor and in
combination the magnetic forces will cause the rotor to spin
another important thing to note is that if you reverse the current in one of the sets of
electromagnets you will reverse the poles for that magnet as the rotor spins a controller will manipulate the current in the electromagnets
making sure the rotor never fully lines up with a magnetic pull and is forced to rotate as you can see the stator creates a
rotating magnetic field and the rotor spins with it the stator rotates the magnetic field faster and faster
forcing the magnet rotate faster and faster as well
accelerating the vehicle since power is a function of both torque and RPM
how much power this motor produces is dependent on a couple factors
first how much current and voltage is being supplied which will increase the strength of the
electromagnets which will in turn increase the torque on the rotor and
also how quickly the current can rotate around the stator which will ultimately play a part in the peak RPM of the motor. "So what
does this all look like on an electric car?" Well using a Formula E car as our example first let's start with the battery
Formula E cars currently have 28 kWh batteries and ultimately the rate at which this battery can discharge
energy to the electric motor will limit how much power it can produce
batteries that can deliver higher voltages to electric motors that can make use of it will result in more power
but another important part of the equation is managing the heat produced in the battery
this is why you'll see teams using dry ice to cool the batteries before they're sent out
to drive to make sure the battery is as cool as regulations
allow for before going out on the track the battery supplies a direct current and the motors use an alternating current
So in the middle we have an inverter which addresses this issue
turning the DC power source into an AC power delivery you can think of the inverter as a device that's
constantly switching the terminals of your battery meaning that the flow of current is
constantly switching the rate at which this inverter can switch the current is of course important for the performance of the motor and the inverters
used in Formula E have switches capable of turning the power on and off over
10,000 times in a second finally that power ends up at our motor which has its own
limitations for creating more and more power the resistance in the wires used limits power and this resistance also generates a lot of heat to
spin the motor with more current you need to be able to cool the added heat.
There are other physical limitations as well, for example the closer the magnets of the rotor are to the stator the better
efficiency and torque you'll have however as the rotor is spinning at
20,000 RPM as you'll see in Formula E the G-forces can cause the rotor to expand slightly which if It weren't accounted for
could lead to contact with the stator so you have to balance the efficiency of the gap you leave,
versus the RPM you want to spin the motor to obviously higher RPMs can mean in and power so ultimately
tuning an electric car will be highly dependent and limited by the hardware within the car much like with internal combustion vehicles if the hardware
isn't at its limit software changes could certainly allow for better performance and efficiency
swapping hardware like using a higher voltage
battery that has more power output could also increase the power of the motors used but that assumes the whole system can handle the added
power and heat hopefully this has provided some insight on how
electric cars work how you can tune them for performance and a glimpse into the world of Formula E, i'll
include a link to their channel if you'd like to see more and as always feel free to leave any questions or comments below.
Thanks for watching!