Observation and Measurement of Electric Vehicle (EV) Components Using Digital Microscopes

Characteristics of EVs

• Eco-friendly because EVs do not emit greenhouse gases.
• Low fuel (electricity) costs for travel distances
• High acceleration performance
• Small number of parts
• Easy maintenance

In-vehicle Motor Structure

Brushless alternating-current (AC) motors are mounted on EVs. There is no brush, which reduces noise and simplifies maintenance.

Rotor

This is an output shaft that drives wheels via a reducer. Permanent magnets are used.

Stator

This part generates force for rotating a rotor. It passes electricity through the stator coil according to the rotor rotation.

Rotor rotation position sensor

This sensor detects the rotor rotation position to pass alternating current that corresponds to the rotor rotation speed through the stator coil.

Types of Permanent Magnets

Ferrite magnet

Ferrite magnets are cheap and easy to form. They are used for in-vehicle DC motors.

Neodymium magnet

Neodymium magnets have magnetic energy that is at least 10 times that of ferrite magnets and are used for EV driving motors. Neodymium magnets are expensive because rare earths are used in their construction. Neodymium magnets are hard but have the drawback that they are sensitive to heat and prone to rust.

Stator Structure

A stator has layers of electromagnetic steel sheets each with a thickness of 0.3 to 0.5 mm.
Electromagnetic steel sheets made from soft magnetic materials are used because magnetic poles need to be reversed instantaneously. The thinner the electromagnetic steel sheets are, the more eddy current can be suppressed in the electromagnetic steel sheets. (Smaller energy losses) Additionally, eddy current losses can be reduced by coating sheet surfaces to insulate them from each other.

ECUs and Inverters

ECUs and inverters used for EVs have the following characteristics.

ECU

ECUs control the electricity that passes through stator coils by calculating the optimal number of rotations and torque. The number of rotations is controlled using the frequency and the torque is controlled using the current.

Inverter

Inverters are components that convert direct current supplied from batteries into alternating current. Inverters not only convert direct current into alternating current but also adjust the frequency and the amount of current during conversion to control the number of rotations and torque of motors.