Updated: Nov 11, 2022
Everything you need to know about electric vehicles. It is no secret that the auto manufacturers are beginning the phase out of the internal combustion engine. In fact, it seems every time we read the news there is some headline from either a manufacturer or the Federal government stating an actual deadline when this will happen.
Do not get us wrong, the ICE isn’t going anywhere any time soon. They will be around in our service bays for decades. Our goal with this new series of articles is to start by explaining how these vehicles work and then move into specific manufacturer designs and operations. After all, ANY electric drive vehicle works pretty much the same way with just small subtle differences. This month we want to just focus on what the manufacturers goals were when building these vehicles. We will cover how the manufacturers met these goals with an extremely basic example of each goal to make it easy for everyone to understand. Future articles will delve deep into system components and how they work, and we will wrap up our introductory articles with a follow the electron explanation before we begin our specific manufacturer designs.
What were some of the goals the engineers had?
1) Make them safe
2) Good range
3) Still have everything we are already used too like A/C, Heat, and headlights for example.
4) Still operate like a vehicle (forwards, backwards, stop and go)
5) Make them reliable
Those are the primary goals! Let us explore some basic overviews of how some of these goals were met. The typical ICE engine uses linear motion and must convert it to rotational motion. Because of the many parts needed to accomplish this, the typical ICE engine has a max RPM range of about 7ooo RPM before we start flirting with disaster. While the electric drive vehicle typically only has around twenty moving parts in its drive train composition. One should note that the shaft of the drive motor also can spin at much higher speeds. For example, a typical Chevy Bolt spins at about 8800 RPM with a maximum speed of 94 MPH. The Tesla rear drive motor on their model “S “can spin at about 18000 RPM! Try doing either of those RPMs with a traditional ICE.
Obviously, we cannot spin the actual drive wheels at those speeds, so we need some sort of gear reduction to occur. This can be done with either a gear box or a transmission assembly. The photo below shows exactly how many basic principles of electric motors operate in a rudimentary fashion. For an electric motor to spin, we obviously need voltage being sent to it, but we also need a magnetic field consisting of at least 1 North and South Pole. Remember playing with those refrigerator magnets as a kid. We learned opposites attract while like poles repel. It is that very concept that causes the shaft to spin by pulling and pushing the shaft towards and away from the magnetic fields.
If we give just power and ground to the assembly, the shaft does not spin until we introduce the red and blue magnetic field. We also see the gear reduction and how the shaft speed will be slowed down to the wheel speed (represented by the orange crank handle) when it spins. In this example we have accomplished the motor part of the motor generator. This makes the car go. If we reverse the polarity to the motor, it spins backwards. Hey, we just explained the goal of forward and reverse and how it is simply created!
Now, if we still have the magnetic field present, but we take away voltage from the motor and spin the crank, it will become a generator and create voltage as indicated by the LED light illuminating. Nice right? But what does this mean for a vehicle? Well, think about regenerative braking. When we take our foot off the accelerator, the module will send a command to the inverter to stop sending voltage to the drive motor. At this time, we still have the forward inertia of a moving vehicle spinning the rotor assembly since it is in some way attached to the drive wheels which are still rotating. When this happens, the rotational speed is greater than the field strength of the magnetic field and we have created the generator portion of the motor generator. We also just experienced a quite simple and rudimentary example of regenerative braking! Next month, we will start to discuss individual components that ALL electric vehicles use and more importantly how they work and how you can diagnose these components!
By: John Forro
AKA: “Electron John”