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Traction motors in electric vehicles

time2020/10/22

New energy vehicles refer to the use of unconventional vehicle fuels as the power source (or the use of conventional vehicle fuels, the use of new on-board power devices), the integration of advanced technologies in vehicle power control and driving, and the formation of advanced technical principles and Cars with new technology and new structure.

1. What is new energy vehicles?

New energy vehicles refer to the use of unconventional vehicle fuels as the power source (or the use of conventional vehicle fuels, the use of new on-board power devices), the integration of advanced technologies in vehicle power control and driving, and the formation of advanced technical principles and Cars with new technology and new structure.



2. Composition of new energy vehicles

Battery (all-electric auxiliary)

In an electric drive vehicle, the auxiliary battery provides electricity to power vehicle accessories.

Charge port

The charge port allows the vehicle to connect to an external power supply in order to charge the traction battery pack.

DC/DC converter

This device converts higher-voltage DC power from the traction battery pack to the lower-voltage DC power needed to run vehicle accessories and recharge the auxiliary battery.

Electric traction motor

Using power from the traction battery pack, this motor drives the vehicle's wheels. Some vehicles use motor generators that perform both the drive and regeneration functions.

Onboard charger

Takes the incoming AC electricity supplied via the charge port and converts it to DC power for charging the traction battery. It monitors battery characteristics such as voltage, current, temperature, and state of charge while charging the pack.

Power electronics controller

This unit manages the flow of electrical energy delivered by the traction battery, controlling the speed of the electric traction motor and the torque it produces.

Thermal system (cooling)

This system maintains a proper operating temperature range of the engine, electric motor, power electronics, and other components.

Traction battery pack

Stores electricity for use by the electric traction motor.


Transmission (electric): The transmission transfers mechanical power from the electric traction motor to drive the wheels.



3. The motor drive system

The motor drive system of new energy vehicles is one of the three core components of new energy vehicles.


In simple terms, the motor drive system is mainly composed of two parts: the drive motor and the motor controller. Among them, the upstream of the motor industry chain is the supplier of raw materials such as electrolytic copper (magnet wire), silicon steel, steel, aluminum, insulating materials, and permanent magnet materials, as well as the supplier of accessories such as bearings and coolers, and the downstream is the vehicle factory.



4. Four types of drive motors

At present, the commonly used drive motors for new energy vehicles mainly include DC motors, AC asynchronous motors, permanent magnet synchronous motors and switched reluctance motors.

From the perspective of the application of different types of new energy vehicle drive motors in China, the current AC asynchronous induction motors and switched reluctance motors are mainly used in new energy commercial vehicles, especially new energy buses, and the actual assembly applications of switched reluctance motors are rare; Magnetic synchronous motors are mainly used in new energy passenger cars.


Performance and type

DC

Asynchronous motor

Permanent magnet synchronous motor

Switched magnetic group motor

Power density

low

medium

high

Higher

Range of rotation/rpm

4000-6000

12000-20000

4000-10000

>15000

Weight

heavy

medium

light

light

Volume

big

medium

small

small

Reliability

bad

good

general

good

Structural robustness

bad

good

good

good

Controller cost

low

high

high

general

Application situation

Eliminated

Currently mainly Tesla applications

Wide range of applications

Currently in the fields of electric buses, household appliances, etc.

Advantage

Low cost, easy to control, etc.

Simple structure, good reliability, easy control of cost

High efficiency, simple structure, small size, etc.

Simple and robust structure, high reliability and low cost

Disadvantage

Complex structure, low speed, large volume, frequent maintenance

Low efficiency, poor speed regulation

Higher cost, magnetic decay at high temperature

Large torque fluctuation and high noise



Motor type

DC brush motor

Permanent magnet motor

AC induction motor

Switched magnetic group motor

Highest efficiency(%)

85-89

90-97

94-95

90

10%Load failure rate(%)

80-87

90-92

79-85

78-86

Maximum speed(r/min)

4000-6000

4000-10000

9000-15000

<15000

Comparison of relative cost per unit output power

1

1-1.5

0.8-1.2

0.6-1

Controller relative price comparison

1

2.5

3.5

4.5

Robust and reliable

good

good

excellent

excellent