EV Fundamentals: Shielded Exrad Cable
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Shielded Exrad Cable
05.40
| 00:00 | In this section of the course, we're going to be looking at the cabling side of electric vehicles, which as you can imagine is pretty important. |
| 00:05 | To start with, let's look at those signature orange high voltage cables, which most people associate instantly with EVs thanks to their distinctive color. |
| 00:14 | Automotive HV cable is a specific specification of cable that's used in EV applications, both in the OEM and EV conversion worlds. |
| 00:21 | It consists of a copper core, insulation, and then an EMI shielding, followed by the final orange insulating jacket. |
| 00:28 | This shielding helps reduce the amount of electromagnetic interference in the vehicle, but it also serves as a protection mechanism for the occupants inside the car. |
| 00:36 | As the shield is connected to the vehicle's chassis ground, if the conductor comes into contact with the shield, the vehicle's isolation monitor will detect this drop in resistance. |
| 00:46 | In a properly configured vehicle, the BMS will then open the high voltage contactors to protect the occupants from electrical shock. |
| 00:53 | High voltage cable is available in all the different sizes you can imagine, from very small wire for low power components like DC-DC converters, to 4-watt cable for super high current applications. |
| 01:04 | This cable is also available in both metric and imperial. |
| 01:07 | So, in metric, the cable sizes are listed as the cross-sectional area in millimeters, such as 95 millimeters squared, and in imperial it's shown as gauge, which you're likely already familiar with if you're watching this course. |
| 01:19 | Many metric and imperial sizes are almost the same, and you can see , which ones are similar in this comparison chart. |
| 01:24 | It's important to understand how to work with EV high voltage cable. |
| 01:28 | So, although this is a fundamentals course for the most part, in this module we are going to learn a little bit about sizing cable based on average current, as well as understanding how to assemble a cable. |
| 01:38 | We'll also share how to do a quick test on a cable to ensure the shielding and the conductor aren't shorting together, and that's going to give you a good insight into how cable assemblies work. |
| 01:47 | We'll also look at the steps involved with building your own cable, although we always recommend purchasing cables if there's a supplier near you that offers custom built and tested assemblies. |
| 01:56 | It's simply good peace of mind as an over or under crimped connection can create big problems. |
| 02:02 | Firstly, when selecting cable size, you need to consider the maximum current, average current, and cable length. |
| 02:08 | The goal should always be to keep components as central as possible and away from the extremities of the vehicle. |
| 02:14 | We want to think about areas of the vehicle that might crumple in the event of an accident and aim to keep our cables further in board so we can protect them in the event of a crash. |
| 02:22 | When it comes to length, shorter is always better. |
| 02:25 | Shorter cables are lighter, they're more efficient, and they're cheaper. |
| 02:27 | There's really no downside. |
| 02:29 | In addition, when all our components are close together, they also make the plumbing and cooling system simpler and more efficient as a result. |
| 02:36 | Because electric vehicles inverters never run at 100% duty cycle, the typical amount of time at maximum current, say it was around 10 to 15 seconds, followed by another 10 to 15 seconds of low or zero current. |
| 02:46 | For this reason, it's not necessary to size the cable in the same way as you would for a load that would be running at 100% duty cycle all the time. |
| 02:54 | Other items that run at a constant load all the time, like DC-DC converters and chargers, should have cable size for a constant load. |
| 03:00 | With that said, these components don't draw very much current, so there isn't a very large weight or cost penalty to go up a little bit in size. |
| 03:08 | Cables exiting the inverter are also running at AC current, not DC. |
| 03:11 | So, this means we need to be sure to use RMS, aka root mean square current, when sizing motor cables exiting the inverter. |
| 03:19 | Here you can see some examples of suggested cable sizes for various components based on the current and length. |
| 03:24 | These can be used as a starting point, and you'll also find this chart linked below the module for future reference. |
| 03:29 | Next, let's look at the job of assembling cables. |
| 03:31 | Keep in mind that every process will be different as each connector type uses a different crimp and shielding drain arrangement. |
| 03:38 | This is another reason why it's always a good idea to have cables professionally made. |
| 03:42 | So, think of this example as more of a generic look at the construction of these cables. |
| 03:46 | Always follow the recommended procedure for the specific make and model of connector you're using. |
| 03:51 | First, the outer layer must be stripped back. |
| 03:53 | Using a sharp blade, the amount we strip back is determined by how much strip length we need for the terminal, plus the gap desired between the terminal and the shielding. |
| 04:02 | We start by making a cut around the circumference of the cable, followed by a slice down the cable to remove the jacket. |
| 04:08 | Be sure not to press too hard, be sure not to press too hard to avoid damaging the shield below. |
| 04:14 | Now, we fold the shield back. |
| 04:15 | Depending on the H-field or shield connection to the component we're working with, different connection methods such as the ferrule or copper tape will be applied to the shield to allow it to interface with the main component, connecting the shield of the cable to chassis ground. |
| 04:28 | Next, we strip the main conductor the specified amount for the terminal being used, and then we crimp with the appropriate tool. |
| 04:35 | It's important here to ensure that there are no shield strands in the proximity of the main conductor, as this will result in a short circuit between high voltage and chassis ground, resulting in any isolation modules reading zero because there isn't any. |
| 04:47 | Using a multimeter, we can now test the cable and shield to ensure that they're an open circuit. |
| 04:51 | Professional cable assembly houses will do this test at a much higher voltage using specialized equipment, which is one reason why it's always a good idea to order cable assemblies when possible. |
| 05:00 | This just isn't a component to cheap out on. |
| 05:03 | Okay, so let's quickly run through the key takeaways from this module before moving on to CAN bus. |
| 05:07 | Orange shielded high voltage cable is the go-to choice for all high voltage cabling in an electric vehicle. |
| 05:12 | Using common cable or welding cable, for example, is extremely reckless when dealing with this voltage level. |
| 05:19 | HV cable is available in a wide range of sizes to suit different uses, and generally, you always want to package your components in a way that requires the shortest length of wire possible, while also keeping these components away from the vehicle's extremities. |
| 05:30 | Lastly, the job of assembling these cables is achievable by a capable enthusiast with the right tooling, but if there's a company near you that provides this service, it's definitely the way to go. |
