System Outline
This system controls the following modes in order to achieve the most efficient operations to match the driving conditions.
- Motor Generator Condition
- The supply of electrical power from the HV battery to motor generator no. 2 provides force to drive the wheels.
- While the tires are driven by the engine via the planetary gears, motor generator no. 1 activates to supply electricity via the planetary gears to motor generator no. 2 to drive the wheels.
- When the vehicle is decelerating, kinetic energy from the wheels is recovered into electrical energy by motor generator no. 2 and is used to recharge the HV battery.
The hybrid vehicle control ECU switches between these modes (1, 2, 1+2, or 3) according to the driving conditions. However, when the HV battery charge is low, the HV battery will be charged by the engine turning motor generator no. 1.
- Inverter
* The inverter converts the high-voltage direct current from the HV battery into three-phase alternating current for driving motor generator no. 1 and motor generator no. 2.
* The activation of the power transistors is controlled by the HV ECU. In addition, the inverter transmits the necessary information for current control, such as the output amperage or voltage, to the HV ECU.
* Along with motor generator no. 1 and motor generator no. 2, the inverter is cooled by the exclusive radiator and coolant system which is separated from that of the engine.
* In a vehicle collision, the circuit breaker sensor installed in the inverter outputs the collision signal to stop the system.
* A boost converter has been adopted in the inverter, which increases the rated voltage output from the HV battery from DC 201.6V to DC 500V. After increasing the voltage, the inverter converts the direct current to alternating current.
- Converter
The power source for the auxiliary equipment on the vehicle such as the lights, audio system, and the air conditioning system, as well as the ECUs, is based on a rated voltage of DC 12V. Because the generator outputs current at DC 201.6V, the converter is used to transform the voltage from DC 201.6V to DC 12V in order to recharge the auxiliary battery. The converter is installed on the underside of the inverter.
- HV Battery
* In the Prius, a sealed nickel hydride (Ni-MH) battery has been adopted. This HV battery has a high power density, is lightweight and long lifespan which match the characteristics of the TOYOTA hybrid system. Because the TOYOTA hybrid system controls the charge/discharge to maintain the SOC (State of charge) at a constant level while the vehicle is operating normally, it does not have to rely on external recharging.
* The HV battery, battery ECU, system main relay and cooling fan have been integrated into a single case which has been placed in the luggage compartment behind the rear seat to make more effective use of the vehicle space.
* A service plug that shuts off the circuit has been provided in the middle of the 28 modules (Rated battery capacity = 201.6V). Before servicing any portion of the high-voltage circuits, make sure to remove the service plug. Please do not put the vehicle in the READY ON state when you have removed, or plan to remove, the service plug. There is a possibility that the battery ECU will be damaged.
* To ensure the HV battery's performance, the battery ECU controls the operation of the cooling fan to reduce the heat that is generated by the HV battery during charging and discharging.
- Regenerative System Operation
This system operates the motor as a generator to change the kinetic energy of the vehicle into electricity when the accelerator pedal is released or manual braking is use to decelerate the vehicle, and then stores the electricity in the battery.