Lightweight, compact and high-efficiency powertrain for EVs
The motor is the source of the power and has extremely low vibrations, and since it can generate maximum torque quickly, it realizes more initial acceleration than a 3 liter-class engine while still being surprisingly quiet.
The e-Powertrain’s main components of motor and inverter were developed by Nissan in order to withstand use in a variety of environments around the world, implementing high performance and high durability.
Further, for the 2013 model year, Nissan LEAF was upgraded with the main components integrated into one unit, making for a lighter and more compact e-Powertrain.
The main units of the e-Powertrain each have their own functions.
Motor: Generates power for moving, and also braking power by the regenerative brake during deceleration.
Inverter: Converts direct-current electricity to alternate current when driving, utilizing the motor, and then recovers energy by converting alternate current to direct current during deceleration (regeneration).
DC/DC Converter: Converts high voltage to low voltage (14V).
Junction Box: Distributes high voltage to every unit, blocking a current pathway like a breaker when anomalies arise.
Reduction drive: Modulates the rotations of the motor and transmits to the tires (drive shaft) (similar to a conventional transmission)
*Car charger: Device for (regular) charging from general alternate current to high-voltage battery
**Power Delivery Module: Integrated unit with charger, DC/DC converter, and junction box
Nissan’s e-Powertrain consolidates the roles of the car charger*, DC/DC converter and junction box into one unit, the PDM**. Moreover, by integrating this PDM with the motor, inverter and reduction drive, the overall space is reduced compared to installing each unit separately, reducing the size.
Motion Power Generation Configuration
The e-Powertrain motor is a three-phase AC synchronous motor, composed of a magnet rotor and coil stator. Passing a current through the motor turns the stator into an electrical magnet, and generates magnetic force. Through this magnetic force, the rotor turns and produces dynamic power. The stronger the magnetic force, the higher the torque. These are the two main methods of raising magnetic force:
1) Using a powerful magnet
2) Applying powerful current
An extremely large amount of power is required to move an object as heavy as a car. Therefore, in general a high output lithium ion battery is used for EV batteries and the motor uses powerful permanent magnets and rare earth materials in order to enhance magnetic force.
The motor in the Nissan e-Powertrain curbs the amount of rare earth material (dysprosium) used as much as possible, and moreover, has been independently designed and developed in order to implement high output and durability. Further, Nissan LEAF’s 2013 upgrade revised the features of the motor and enhanced efficiency for frequent driving in towns and cities.
Regenerative Brake Configuration
Turning a motor by hand without current passing through it generates a current in the motor, while simultaneously producing force stopping the motor rotation. The faster the motor is turned, the greater the current and the force stopping the rotation. The regenerative brake utilizes this current and the force stopping the rotation.
Stepping on the brake while an EV is running stops the supply of electrical current that had been until then rotating the motor. As the supply of current stops, the force of the tires moving rotates the motor. Doing this then generates a powerful current through the motor and also force applied to reduce tire rotation. The current can charge the battery via the inverter, while the force reducing the rotation serves directly as a braking function on the tires.
A regenerative brake is more effective the higher the rotations of the motor (i.e. the faster the vehicle speed). In general, a friction brake is used at low speeds but the Nissan e-Powertrain is able to regenerate even when vehicle speed is a mere 3km/h, resulting in high energy regeneration efficiency.
EVs and hybrid vehicles use regenerative braking, which utilizes the motor to convert the kinetic energy during deceleration into electrical energy. With energy regeneration, an EV is able to run on less electricity and a hybrid vehicle on less fuel.The EDIB (Electric Driven Intelligent Brake) allows and controls optimization of the regenerative brake and regular friction brake (hydraulic brake).
After stepping on the brake pedal, the system produces natural and adequate braking force that corresponds to the operation. The amount of energy regeneration also needs to be increased as much as possible.EDIB (Electric Driven Intelligent Brake) controls the regenerative brake and friction brake to support both of these requirements. Further, it also controls the reactive force from the pedal in order to unify the feeling when stepping down on the pedal and the sense of deceleration.
When the driver steps on the brake pedal, the stroke sensor detects operation of the brake. That information is communicated to the ECU and controls the motor. The motor engages the piston and amplifies the friction brake’s pressure (hydraulic pressure). Through optimum control of the friction brake’s hydraulic pressure, the energy regeneration outcome is maximized.
Source: Nissan – Global