58 Electric and Hybrid Vehicles FIGURE 3.6 Power-split pre-transmission hybrid configuration. Wheel M/G FD Wheel FIGURE 3.7 Parallel post-transmission hybrid configuration. 3.2.2.2 P0–P4 Hybrid Architectures The electric machine within the electric drive is the link between the electrical system and the vehicle system with the pre- and post-transmission arrangements broadly defining the location of the electric drive with respect to the transmission. The pre- and post-transmission arrangements are further classified by the industry as P0, P1, P2, P3 and P4 architectures based on the type of the connection between the electric machine and the powertrain such as belt, integrated or gear mesh.
The P0, P1 and P2 architectures are pre-transmission type, while P3 and P4 architectures are the post-transmission type. The four connection type-based architectures are described below with their configurations shown graphically in Figure 3.8. P0 – The electric machine is connected with the internal combustion engine through a belt at the front end serving as the replacement of the traditional alternator with higher power rating and regeneration capability. This electric machine is also known as the belt starter generator (BSG). P1 – The electric machine is connected on the crankshaft side of the IC engine through a gearset. This is an integrated starter generator (ISG) arrangement.
Neither P0 nor P1 architectures allow the mechanical disconnection of the electric machine from the IC engine. P2 – The electric machine is side-attached to the transmission through a belt or gearset and is decoupled from the IC engine through a clutch rotating at IC engine speed or geared to rotate at a multiple of IC engine speed. The pre-transmission hybrids with planetary gear- set connections are of P1 or P2 type. P3 – The P3 is a post-transmission configuration with the electric machine connected with the transmission through a gear mesh. The electric machine is decoupled from the IC engine and rotates at a multiple of wheel speed.
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