Both BYD DMI DHT and Changan’s New Blue Whale iDD DHT are leading players in the hybrid market, featuring the same P1+P3 structure. When comparing the two models, such as BYD Qin PLUS and Changan Qiyuan A05. there’s little difference in terms of parameters, acceleration performance, and minimum charging fuel consumption. At first glance, one might think Changan copied BYD, but upon closer analysis, there are significant differences in the electric drive structure.
BYD DMI Structure:
The BYD DMI uses a parallel axis structure, with the P1 and P3 motors being four-pole high-speed motors, capable of reaching a maximum speed of 16.000 rpm. To match the engine, the P1 motor transmits power through a reduction gear set connected to the engine shaft. At the end of the engine shaft, there’s a hydraulic clutch controlling the coupling or decoupling of the engine, P1 motor, and output shaft. The P3 motor is also connected to the output shaft using a set of gears with the same ratio. This design gives the DMI hybrid box four parallel shafts: the engine shaft, P1 motor shaft, P3 motor shaft, and intermediate shaft.
Changan New Blue Whale iDD Structure:
The Changan New Blue Whale iDD’s electric motor and engine share the same axis, and its P1 and P3 motors are sixteen-pole motors, with the same torque output but at one-quarter the speed of four-pole motors, allowing them to connect directly to the engine shaft. The P1 motor integrates a hydraulic clutch, enabling the coupling or decoupling of the engine, P1 motor, and output shaft. Changan’s DHT hybrid box uses a simpler three-shaft six-gear structure with higher integration. The key lies in the P1 motor's eight-layer flat wire winding and the P3 motor’s ten-layer flat wire winding, both of which are much denser than BYD's six-layer winding. This allows Changan’s DHT motors to significantly reduce their axial length while maintaining high power output at lower speeds.
Advantages of Changan’s Electric Drive:
1. The P1 and P3 motors are coaxial, eliminating the power transmission loss from gear reduction.
2. Under the same vehicle speed conditions, the P1 and P3 motors rotate at only a quarter of DMI’s speed. The benefits of lower speed include reduced noise and longer lifespan.
3. Higher integration and a more compact structure—Changan’s New Blue Whale iDD hybrid box weighs 30 kg less than BYD’s DMI and has a smaller external size.
Although the two systems differ structurally, their operational modes are quite similar. This single-speed DHT hybrid box can achieve the following modes:
1. EV Mode: The clutch disengages, and the engine and P1 motor are inactive, while the P3 motor drives the vehicle. During deceleration, the P3 motor generates electricity to recharge the battery.
2. Series Drive: The clutch disengages, and the engine drives the P1 motor to generate electricity for the P3 motor, which powers the vehicle. Excess electricity is stored in the battery. During rapid acceleration or uphill driving, the power generated by the P1 motor and the battery’s energy are combined to power the P3 motor. Parking charge mode is also a form of series drive, often referred to as range-extending mode.
3. Engine Direct Drive: When the vehicle speed reaches the engine direct-drive threshold (typically above 70 km/h), the clutch engages, and the engine directly powers the output shaft to drive the vehicle. During rapid acceleration, the P3 motor draws electricity from the battery to assist the engine. During deceleration, the P3 motor generates electricity to recharge the battery.
