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PDM Installation & Configuration: PDM Mounting Considerations

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PDM Mounting Considerations


00:00 - In this section of the course, we're going to move away from the pure theory side of things and discuss some of the more practical aspects of using a PMU in your automotive electrical project.
00:10 To start, let's discuss the physical mounting of the PMU.
00:13 The PMU you've chosen for your project will have a specific intended mounting solution built into its design.
00:21 This could be mounting tabs off the edge of the case, recessed through holes for flush mounted screws or a specific detachable bracket which is included with the device.
00:29 In any of these scenarios, I would advise you to stick with the manufacturer's intended mounting solution because they'll typically have gone this route for a pretty good reason.
00:39 The two main concerns we have when it comes to PMU mounting are heat and cable routing.
00:44 These concerns are also valid for any of the other electronic components of a car but let's have a look at each and talk about why they're critical to get right for our PMU.
00:54 A PMU can be responsible for handling large electrical currents and this tends to come with the byproduct of heat.
01:01 Particularly if your PMU is capable of and you're making use of PWM control, heat build up in the PMU is a critical concern.
01:09 The MOSFETs inside the PMU will most likely be mounted in such a way that their case is in direct contact with the inside of that PMU housing.
01:19 This is done so that the housing can be used as a heat sync for the MOSFETs, wicking away the heat they generate and dissipating it out to the atmosphere.
01:26 This is why you'll see some PMUs designed with integrated fins as part of their housing, it's to increase that surface area available for dissipating this heat.
01:35 For this to work, we need to ensure that the PMU is mounted in a reasonably open location and not tucked away behind vehicle carpet or in an enclosed space like a glove box.
01:45 I recommend mounting your PMU to a flat sheet metal piece of the vehicle interior or to a flat metal bracket with specfic mounts to attach to the vehicle interior.
01:55 This is because the PMU will also use the area where it's in contact with the surface it's mounted to in order to sink away the heat.
02:04 Now this of course will only work if the part of the body that the PMU is mounted to isn't getting hot from being close to an exhaust or other heat source so make sure you keep this in mind as well.
02:15 Let's have a think about the cable routing which is another major concern when we're working with the PMU for a couple of reasons.
02:22 The first of these is that the main power connection to the PMU is likely to be a larger, less flexible cable.
02:28 Many PMUs have a threaded stud for their primary power connection and this can actually be quite advantageous because it allows a wide range of angles for this connection to be made where it enters onto the PMU.
02:40 However the main power connection is made to the PMU, you'll need to keep this in mind when choosing the mounting location and orientation of the PMU to avoid unnecessary cable or connector strain.
02:52 The second cable routing concern is insulation.
02:55 It's common for the main power input to the PMU to be a direct connection to the battery with no fusing in between.
03:02 For this reason, the cable needs to be supported along its route throughout the vehicle to prevent abrasion and always pass through bulkheads via an insulated threaded stud or a supporting cable gland or grommet to make sure there's no chance of the bulkhead cutting that cable.
03:18 The vehicle body is almost always directly connected to ground so if there's an inadvertent connection made between the large supply cable and the vehicle body, a fire is almost going to be guaranteed which is something we definitely want to avoid.
03:33 In this module we've talked about the physical mounting considerations to be aware of when installing a PMU.
03:38 You need to be aware of heat buildup in the device making sure it's not tucked behind carpet or in a small enclosed space.
03:44 The planning of the main input supply connection routing is also critical as these cables are less flexible and any damage to their insulation is a major safety risk.

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