Original URL: https://www.fangzhenxiu.com/post/773963, published on 2020-07-01 I previously published an article briefly analyzing the Audi e-tron electronic control unit. During the New Year holiday, I went abroad on business and downloaded some videos along the way, including ones covering the working principle of the Audi e-tron powertrain and the Audi e-tron production process. These videos can all be found on ***. At the time, for convenience — and because I was too busy after the Chinese New Year — I didn't organize them into written form. The main content of this article comes from several videos. After watching them carefully many times, I compiled this article, which took considerable effort. I hope it will be helpful to everyone. I also plan to produce a video later covering all the points.
The Audi e-tron powertrain is divided into front-drive and rear-drive versions. The front-drive power is 125 kW, and the rear-drive power is 140 kW, as marked in the videos. The difference is that the front-drive uses a parallel-shaft electric drive axle, while the rear-drive uses a coaxial electric drive axle, as shown in the figure below illustrating the Audi front-drive and rear-drive powertrains. There are some differences in the water channels between the front and rear drives.
The overall structure is as follows. This is the 3D image of the front-drive unit. The electronic control unit — the same electronic control promotional material can be found on Hitachi's official website. There is currently no information available to confirm whether the electronic control unit is supplied by Hitachi.
(1) is the three-phase wiring compartment, which can be opened to connect the three-phase wires between the motor and the controller; (2) is the busbar wiring compartment, which can be wired on both the left and right sides; (3) is the breather valve; (4) is the water inlet/outlet. The front-drive and rear-drive water inlets/outlets are different.
Remove the three-phase wiring compartment cover. The 3D drawing above is the front-drive version; the actual unit below is the rear-drive version. The wiring method is the same.
The rear-drive water inlet/outlet is clearly different from the 3D drawing. This drawing is of the rear-drive coaxial axle.
Today I will mainly introduce the electronic control unit. The image of the electronic control unit is shown below. From its appearance, it is quite distinctive — like a shovel, or like a flyswatter. The protruding section with two wiring holes is where the high-voltage busbar connects. This design accommodates different routing methods, allowing connection on either the left or right side, which increases flexibility during vehicle assembly. Next, let's look at the exploded view. All components can be seen in the exploded view. We will now explain each part.
Remove the cover and extract the entire electronic assembly. It can be seen that there is a clearly visible flexible flat cable at the bottom of the housing. This is the low-voltage connection terminal for external connection. From the 3D drawing, it uses a flex-rigid connection board (1), whose main function is low-voltage power supply, communication, and other low-voltage signals; the connection between the driver board and the control board (4), as seen from the 3D drawing, is also via a flexible flat cable, but the cable runs above the three-phase wires, which in theory is unfavorable for EMC. The two white wires in the figure are the harnesses for the busbar Hall sensor and the three-phase Hall sensor (3). The three-phase Hall sensor uses an integrated Hall sensor design. Near the busbar interface there is an oval magnetic ring — this is the EMC magnetic ring (2). (5) is the busbar Hall sensor.
As shown below, (1) is the water outlet, (2) is the water inlet.
Open the housing cover. (1) is the busbar routing, (2) is the busbar Hall sensor, (3) is presumed to be cover-open protection.
Take the entire electronic unit out of the housing. (1) is the busbar copper bar, which uses a laminated busbar. There are two extra terminals on the busbar; I could not determine their purpose. The busbar copper bar is divided into three sections: one section is the terminal box plus magnetic ring, one section runs from the magnetic ring to the busbar capacitor, and the busbar capacitor is another section. The second and third sections are shown in (6); (2) is the drive transformer, (3) is the IGBT signal connector, (4) is the connector between the driver board and the control board. No driver chip is visible on the driver board — it should be on the back of the driver board. (5) shows the two terminals that route the busbar to the driver board, presumed to be for busbar voltage sampling. The Hitachi logo is clearly visible on the driver board, confirming that the controller is supplied by Hitachi for Audi.
(1) is the water channel inlet. At the inlet, in addition to flowing to the IGBT water channel (4), a portion also flows into (3). Section (3) is adjacent to the busbar capacitor, which is presumed to provide water cooling for the busbar capacitor. (2) is the water channel outlet, flowing toward the motor.
The diagram below is a bit cluttered. This shows all the components in the exploded view: (1) driver board, (2) driver board bracket, (3) high-voltage busbar sampling harness, (4) three-phase output laminated copper bar, (5) three-phase copper bar, (6) integrated busbar Hall sensor, (7) Hitachi double-sided water-cooled IGBT module, (8) laminated busbar, (9) water outlet cover plate, (10) IGBT cooling water channel, (11) busbar capacitor, (12) positive (or negative) busbar — it is not known which is positive or negative, (13) water inlet cover plate, (14) control board, (15) capacitor pin solder joints, (16) IGBT middle four-pin solder joints, (17) IGBT thick pin solder joints, (18) cover plate at the other end of the IGBT water channel.
From the entire exploded view, it can be seen that the water channel is quite complex, especially the waterproofing aspects. (7), (9), (10), (13), and (18) all require waterproofing, and all are inside the housing. The driver board clearly bears the Hitachi logo, and the IGBT module is presumed to be a Hitachi IGBT — a dual-sided water-cooled module. Of the five thick pins in the middle, four thinner ones should be positive and negative inputs, and the largest one is the three-phase output. Whether it is the positive/negative laminated busbar or the three-phase laminated busbar, the manufacturing process is relatively complex. The busbar capacitor approach has reference value: individual four-pin capacitors are about half the cost of custom modular capacitors, but how to minimize parasitic parameters requires everyone's imagination. The capacitor is also water-cooled.
Water channel design: the water channel first flows through the controller and then through the motor. Inside the motor, the water flows through both the motor wall and the interior of the rotor. The general routing can be judged from the video and the direction of heat conduction. Water flows from the inlet, first past the capacitor side wall, through the three IGBTs, into the rotor, and after exiting the rotor, flows through the motor housing and then out.
The figure above shows the front-drive water channel; the figure below on the right shows the heat conduction diagram of the rear-drive water channel. In the rear-drive, after the water flows through the IGBTs, it enters the motor — first flowing through the motor housing, then into the rotor, and then out. The specific difference between flowing into the housing first versus the rotor first is not entirely clear, and I look forward to readers discovering it.