This is the first of two explainer videos I’ve created to help YouTube viewers understand the concepts, terminology and physics of what’s going on in my Caterham Seven EV conversion.
I’ve made the videos so I don’t need to keep explaining each concept every time I mention it in a subsequent video and I’ll be referring you back to these videos as I progress with my conversion.
In this first of the two explainer videos I cover the basics of the two forms of electricity, Alternating Current (AC) and Direct Current (DC), used in modern EVs. I also cover how multiple AC phases (3-phase) is used in practice.
The second video will go into more detail about the different components I’ll be using in my EV conversion.
TLDR;
Ok, so the “Too Long Don’t Read” of this video is that it, and its follow along sibling, have taken me 8 months to produce. The 9 minutes of this video and the 19 minutes of the second have taken FOREVER to get done, and don’t really reflect the time that’s gone into them. I’ve created countless animations and scripts, and then editing it all together has taken an age too.
Most of the 2D animations (block diagram, battery cell animations, battery animation, AC and DC simple circuits) were done in Apple Motion (the video is done in Final Cut Pro).
The 3D animations are all done in Blender (motor internals, car, car and charger, car being charged, fast charger scene, torch and house being lit etc ).
The biggest of those tasks has been the Motor Internals animation in Blender. I’ll cover that in the post about the second video (here when it’s published).
For this Electric video, the major element was the creation of the oscilloscope Apple Motion generator.
Battery Generator
Ok, so lets start off with the first generator I created for this Putting the EV In Seven mammoth YouTube project. I knew I was going to need a bunch of animated video elements to explain stuff as I go about the EV conversion, and so I thought a battery generator would bound to be needed at some point.
You can see a few example configurations in the image above, and the parameters in the image below. By animating each of the scale parameters I can make the batteries look as though they’re filling or emptying.
Oscilloscope Generator
This generator allows me to animate both DC and AC waveforms, along with some of the controls (time base). By creating the animation in Motion and then publishing the opacity of each animation element, I can mix and match a whole bunch of different animation combinations.
To me, using the Oscilloscope makes perfect sense for trying to explain how direct current and alternating current happen over time.
Apple Motion AC and DC Circuit Generator
Another Apple Motion creation was a quick animation to demonstrate the differences between current flowing in both AC and DC circuits.
Again, this was a case of builing in previous work. I’d already created a battery animation widget (see above) and also managed to animate blobs along wires for the main EV circuit diagram (see here). So I mashed both of those together along with an animated switch and light bulb to create an animation.
The widget has controls to control various features but also allows two types of current flow to be animated – one way for DC and oscillating for AC.
It’s More Complicated Than That
I’ll cover this in more detail in the second post (here). But I’ve simplified the Motor Internals and the Three Phase AC concepts in these videos.
Motor Internals are a simplification because a real Permanent Magnet Synchronous Motor (PMSM) would have both more stator windings and more permanent magnet poles. I may make a future video that better replicates both aspects, but that would be more to create a WOW! Factor rather than being particularly useful as an explainer.
Again, I’ll cover this in the second post, but I’m really happy with the way the motor internals animations have come out. Here’s a YouTube clip of just the motor internals…
And that’s it for this post. Hopefully, it was helpful.
Video Chapters
- [00:00] Introduction
- [00:29] Project Overview
- [02:29] The Electric Bit in Electric Vehicles
- [02:59] Oscilloscopes
- [04:09] Direct Current
- [04:56] Alternating Current
- [06:52] Three Phase Alternating Current
- [07:34] Safety
- [07:50] Training
- [08:31] Wrap-up
Transcript
Introduction
[00:00] As you can probably guess, the key to an electric car is, well, the electric. In this 1st part of my EV Tech miniseries, I’m going to take a look at what the electric and electric vehicle means. This miniseries. Will hopefully give you all the background you’ll need. To follow along with my ultra no frills, Kate from 7, electric vehicle conversion.
Project Overview
[00:33] This video is part of my Putting the EV in Seven projects. Well, we’re taking an unloved 10 year old Caterham 7 drift car and converting it to be an electric vehicle. We’re removing the internal combustion engine and putting in an electric motor, batteries, and control electronics to create an EV interpretation of the classic 1957 pocket rocket. At the end of which, we hope to be able to say whether converting such an iconic car really is an option for future conversions. As the project progresses.
[01:01] There’ll be a mixture of explainer. And progress videos. But it’s… Explain videos. That I’ll keep asking you to… come back to, if you want. And what some widget or other does. These explainer videos are going to be relatively technical. So I’ll try and keep the content to about high school level physics and then explain the more technical stuff as we go. As such. I’ll be glossing over some of the more nuanced aspects of EV design. So if you’re a more advanced viewer, please just accept that I’ve glossed over anything beyond the basics.
[01:31] Let me know in the comments, if you’d like to see some videos that go into the more advanced stuff. The 1st explain the video. Is all about electricity, covering the basics of different forms of electricity used in an EV. And the 2nd video. More detailed look at the components we’ll need to use. In the conversion. And I look at the block diagram. Of the project. At that point, We should have all the basic principles of a no frills EV nailed down.
[02:01] And. To the actual progress of my project car. And if this is your 1st time watching this series, Then my intro video. which you can find in the video description. We’ll give you some of… Why do this? Along with the background to the project. And what I’m trying to achieve. So to get us going, we should start by making sure we’re up to speed on some of that high school physics I was talking about earlier. And specifically one key aspect of an EV.
[02:25] The electric bit in electric vehicle.
The Electric Bit in Electric Vehicles
[02:30] Fundamentally, the electricity in an electric vehicle is all about making it go. Instead of burning fossil fuels, In an internal combustion engine. We use electrical power to turn a motor to make us move forwards or backwards. To break that electric down. A bit further. We use 2 forms of electricity in an EV. Direct, current. An alternating current. AC and DC are both just electrons moving around an electrical circuit, and to explain the content. I’m going to use a diagram of. Vanisilloscope.
Oscilloscopes
[03:01] And oscilloscope. Displays time along the horizontal axis. And voltage on the vertical axis. A scope can therefore show us voltage levels as time passes. As well as showing us voltage, scopes are good at showing us high speed events. By adjusting the time it takes for the scope to draw on the screen. Known as its time base. We can take very high speed voltage changes. And capture them like we’re using a slow motion camera. Oscilloscopes display voltage. So what’s all this about direct and alternating current?
[03:32] Well, voltage and current changes in an electrical circuit are related to each other. As one changes, so will the other. This relationship is not. Zones law, and is written as V equals I times R. Or voltage equals current times resistance. And so we can see if we increase the voltage. So the current would also increase too. We could get more in-depth here, looking at some other forms of resistance known as impedance. But this is one of those bits we’re going to gloss over for the moment.
[04:00] And just say that if we’re interested in currents in a circuit. Then we can infer what’s going on. By looking at the voltage on an oscilloscope screen.
Direct Current
[04:10] Direct current. Or DC. Is used to store electrical power in the vehicle’s battery pack until we need it. And in some cases, it’s also used to charge the vehicle too. Direct current. refers to a constant current or voltage supply that doesn’t change over time. You can see that as the scope draws a DC voltage across its display. A battery and a torch is a good example of a DC voltage supply. When we turn the switch of the torch on. The DC voltage of the battery.
[04:36] Allows the current to flow around the circuit. The electrical energy is used up by the resistance of the light bulb. Which heats up the bulb filament, making it glow to give off light. Again, we’re glossing over fluorescent and LED lights here for the sake of simplicity. The key thing here is that we can store the energy you needed to light the torch in the DC powered battery.
Alternating Current
[04:56] Alternating current. Or AC. Is used to make the motor turn. And because we have both those forms of electricity, we’ll also. have to convert the DC power from the battery. Into AC power for the motor. We’ll talk about that in more detail in part two. this video series Here we can see an alternating current being displayed on the scope screen. Its voltage switches between both +and negative as time passes. Remember, we’re interchanging current and voltage here because we’re glossing over things.
[05:24] In this case, the line being drawn is a sine wave and we’ll come back to that in a bit. With AC circuits, electrons 1st flow in one direction and then the other. We can create a similar light bulb circuit to the battery and torch we saw earlier. But this time, the current source is… Electricity grid, sometimes called Mains. And the bulb is a home light bulb. But this time, When we turn… On the switch. The current flow isn’t just flowing in one direction.
[05:50] It alternates or changes direction. In mains or grid supplied AC electricity? The switch from one direction to the. Another takes the shape of a sine wave. The voltage repeatedly rises and falls between a positive peak and a negative peak. The number of times the sine wave repeats per second. is known as its frequency. And we can measure it in cycles per 2nd or hertz. One hertz is one sine wave cycle per 2nd. Now we know the basics of alternating current. Let’s look more closely at EVs, where the AC also has another couple of key characteristics.
[06:23] Firstly, the AC in an elect. vehicle has a highly variable frequency. It will go from 0 Hertz, remember Hertz’s cycles per 2nd, when the car is stationary, up to many 1000s of cycles per 2nd when the car is at full speed. Well, come on to this again. in later videos. But the frequency of the AC power that’s fed to the motor is what determines how fast it spins and how fast we go.
Three Phase Alternating Current
[06:54] Most modern EVs. Use AC to drive their motors. But they also typically use what is called 3 phase AC. 3 phase AC. Is 3 of the sine waves we’ve been talking about to this point. Apply to the motor at the same time. Each sine wave is called a phase. Whether 3 phases… will have the same voltage. And frequency. But offset by 13rd of a cycle.
[07:25] Now we know what AC and DC are. There are two final things to bear in mind while talking about EV electricity.
Safety
[07:33] Firstly, safety. Electricity is dangerous. The sorts of currents and voltages will be using in our conversion could kill. So we need to be careful to use appropriate procedures and clothing when dealing with live components. I also strongly recommend that if you’re… thinking of doing your own EV conversion.
Training
[07:50] Then take an EV safety course. A well put together course. We’ll give you an. Understanding of the dangers. As well as important practical experience. Of how to be safe when working with high voltages and currents. I took a course from Felton. But there are recognized courses popping up in most countries now. Secondly, all this talk of voltages and current flowing sounds pretty simple, right? Well, it’s actually way more complicated than that in practice. There’s a lot of electromagnetic and electrical theory to get into.
[08:17] If you really want to understand the physics of how an EV works. And as we’ll see in future videos, it’s not just about the theory, there are very practical consequences of high voltages and currents flowing around the vehicle.
Wrap-up
[08:32] In this 1st part of our understanding EV Tech miniseries. We covered. How DC has a constant voltage and is used to store electrical energy in a battery? how AC changes over time and that we use 3 phase AC to power a motor. And part 2 will cover the basic components of my simple EV conversion. If you’d like more in-depth videos on anything I’ve covered here, then please let me know in the comments section below, and I’ll do my best to put one together.
[08:59] So stay tuned. Hit the like button to help out the channel and the subscribe button to get updates as they come. And as always. Stay safe and happy blatting.
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