Toyota Prius Study case. Toyota Prius Concept Building Operation Electrical machines.

Toyota Prius

Study case

Toyota Prius

Concept Building Operation Electrical machines

The Toyota Hybrid System

The Prius evolved from 1997 to 2000 In 2003 Toyota increases the motor output by 50% (THS II) The THS transmission is indicated by the dotted outline

The Toyota Hybrid System The system’s main elements are:

A power electronic unit A main processor HV battery MG1 and MG2 Skid and break

control unit


The hybrid transaxle MG1, MG2 and the engine are on one axle A planetary unit ensures coupling of the

motors A silent chain and a differential provide

motion transition to the wheels


This system controls the state of charge (SOC) The SRMs control and limit the current

flow into and out from the battery The target of the SOC is about 60%

controlled by the battery ECU


The power electronic of the THS is composed of: The boost converter Two inverters (one for each machine) DC-DC converter AC converter


The DC-DC converter ensures the charging of the auxiliary low voltage battery of the machine

It has a H-bridge to invert the cc into high frequency ac The transformer lower the ac voltage and rectify it to 12Vcc


The AC inverter ensures the ac for the air-conditioning compressor This was introduced from 2004, changing the HV’s 201Vcc into

206Vac


The regenerative break system control By this, the loss of kinetic force to heat and friction is diminished and

transformed into electrical energy Distribution of force balance


The assisted break system was implemented in 2004 Is senses the speed and the force on of the pedal when it is pushed

and function of this, and of other sensor’s response it increases the hydraulic pressure.


The EPS system assists the steering based on: Torque sensors Data from additional sensors regarding the machine condition A DC motor

The THS operation

The THS improvements

Bus voltage 274V to 500V then to 650V The torque is reduced and the speed is increased Downsizing of the motor, reduced the motor weight, hence low

center of gravity offering the possibility of mounting on one shaft the traction drive motor, the generator, the power distribution and the engine


Reducing the iron losses is mandatory Losses were reduced with over 30%

10% due to improvement of reluctance torque

20% due to using high grade steel 5% due to design considerations

The efficiency of the motor is 95%,


The THD of the air-gap flux density must be decreased as much as possible

The shape and the arrangement of the permanent magnets is crucial


The bridge is used to ensure mechanical stress and supports the flux barrier

The bridge must be sized as small as possible The number and size of the bridges reduces the mechanical stress

predicted for the manufacturing process and other final stage issues


Experimental results of the 2005 motor design

Wise use of the reluctance torque


The noise is due to the switching frequency that creates an AC field in the core of the inductor

Frequency over 20kHz is recommended to be used in HEVs The phenomenon is called “magnetostriction” (the core expands and

contracts) More Si (from 4% to 6.5%) was added in the material for the core’s

lamination


The noise given also by the power switches, the machine housing and the vibration of different body parts, was diminished by countermeasures, noise absorbing and insulation materials applied to the body

Conclusions

The Toyota Prius has a complex system based on several sensors all operating together to fulfill the control of the vehicle’s behaviour

A lot of improvements were added to increase the benefits of using a Toyota designed HEV

The PMSM used for the Prius proved to fit all the requirements perfectly reaching the desired output power and torque

The optimal structure is achieved testing several permanent magnet arrangements, considering the solution to place them along the flux paths

Using 3 bridges proved to fulfill the requirement of low air-gap flux density THD

The noise due to switching and vibrations were reduced to a convenient target

Thank you for your attention !

Toyota Prius Study case. Toyota Prius Concept Building Operation Electrical machines.

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