Originally published on 2020-04-13, original URL: https://www.fangzhenxiu.com/post/595116
The Audi A3 e-Tron inverter analysis is divided into three major sections: (1) housing and cooling unit; (2) DCDC controller; (3) motor controller. Due to limited time and capacity, it is difficult to organize, translate and proofread large amounts of text within a few hours, so the content can only be presented in several parts. Your attention, support and sharing are much appreciated.
The inverter power module of the Audi A3 e-Tron is designed and manufactured by Bosch. The inverter power module is divided into two parts: the three-phase AC motor controller and the DCDC unit. It weighs 10.2 kg, measures 371 mm × 217 mm × 194 mm, has a volume of 10.2 L, and costs approximately USD 752.
Figure 1: Audi A3 e-Tron inverter
The Audi A3 e-Tron inverter will be introduced in the following three parts: housing and cooling unit, DCDC controller, and motor controller. The DCDC controller and motor controller are further broken down into internal housing, busbars and three-phase copper bars, PCBA, ferrite, busbar capacitors and wiring harness.
Figure 2: Exploded view of the Audi A3 e-Tron inverter Figure 3: Names of the components in the exploded view of the Audi A3 e-Tron inverter
(1) Audi A3 e-Tron inverter housing and cooling unit
The Audi A3 e-Tron housing and cooling unit includes the external main housing, the bottom cover, and a cooling plate dedicated to cooling the internal components. The components in this group include: a double-sided cooling plate, the main housing, a small top cover plate and the bottom cover; the double-sided cooling plate and the main housing are both die-cast parts; of the two covers, one is a die-cast part and the other is a stamped part; coolant pipe connectors, sealing rings, and associated hardware such as screws, connectors and labels.
Figure 4: Audi A3 e-Tron inverter housing and cooling unit
The double-sided cooling plate is designed as two castings made of A380 die-cast aluminum. The manufacturing process for these two castings includes casting, gate trimming, machining, deburring and cleaning. After the initial processing of these two parts, they are assembled and appear to be friction stir welded together. Post-weld machining of the welded assembly provides a sealing surface for the weld before final assembly. Both sides of the cooling plate have machined pads (heat sinks) for electronic devices. One side is used for heat dissipation of the DCDC controller, and the other side is used for cooling the IGBTs of the motor controller.
Figure 5: Audi A3 e-Tron motor controller IGBT cooling plate Figure 6: Internal cooling channel 1 of the Audi A3 e-Tron inverter cooling base plate Figure 7: Internal cooling channel 2 of the Audi A3 e-Tron inverter cooling base plate
The main housing is a large die-cast aluminum part. The material is considered to be aluminum A380. After casting, the part undergoes trimming, machining, deburring and cleaning. The main housing includes mounting features for the cooling plate, low-voltage harness terminals and a high-voltage harness compartment for busbar and three-phase line connections.
Figure 8: Audi A3 e-Tron inverter main housing Figure 9: Busbar and three-phase line terminals with the main housing removed
The top small cover assembly includes a cover plate, a gasket, a support bracket for the cover-opening protection switch, and a protection switch mounted on the inner surface of the top small cover. The top small cover is considered to be a machined die-cast A380 aluminum plate with the function of mounting the cover-opening protection switch, the gasket and the cover-opening protection switch bracket assembly. The gasket and cover-opening protection switch bracket use a two-shot injection design, with a silicone-based gasket material and a polybutylene terephthalate (PBT) cover-opening protection switch support bracket. The cover-opening protection switch consists of two terminals (assumed to be a shorting bar) molded onto a PBT housing. The switch is secured to the inner surface of the cover with a pair of screws.
Figure 10: Audi A3 e-Tron inverter top small cover assembly Figure 11: Audi A3 e-Tron inverter top small cover gasket and cover-opening protection switch support bracket Figure 12: Audi A3 e-Tron inverter cover-opening protection connector
The bottom cover assembly includes the bottom cover, a silicone ring and a pair of foam pads. This bottom cover is considered to be stamped aluminum. A pair of die-cut peel-and-stick foam pads is placed on the inner surface of the cover. The cover is sealed with a silicone-based sealant applied around the perimeter of the bottom cover. The bottom cover is fastened to the housing with screws.
Figure 13: Audi A3 e-Tron bottom cover assembly Figure 14: Audi A3 e-Tron inverter coolant nozzle