Permanent Magnet & InducƟ on Motors for Electric Vehicle

Permanent Magnet & Induction Motors for Electric Vehicle

Electric vehicles are gaining ground and many automoƟ ve companies are launching their electric cars. It is expected that in future electric vehicles will be the main mode of transportaƟ on.

These vehicles are cleaner and more effi cient as they have less number of moving parts than IC engine vehicles. They run on electric drive systems, electric motor, which converts electrical energy into mechanical energy, is the major part of the propulsion subsystem of the electric drive systems.

InducƟ on Motor is one such type of motor which is popular in electric vehicles. It is followed closely by Permanent Magnet motors. Well known electric car Tesla model S relies on inducƟ on motor while motor in Nissan Leaf and recently unveiled Porche’s Turismo concept vehicle is permanent magnet synchronous motor.

InducƟ on motors have benefi ts like low cost, high reliability and maintenance-free operaƟ on. It is an asynchronous type of motor so the rotor always rotates at a lower speed than the magneƟ c fi eld. It relies on electric current to turn the rotor and produce torque. The electric current is generated through electromagneƟ c inducƟ on from the magneƟ c fi eld of the stator windings. InducƟ on motors can be used without a variable frequency drives (VFD) and are also cheap to manufacture.

However, convenƟ onal control of inducƟ on motor such as variable voltage, variable frequency cannot provide the desired performance and they also suff er from lower effi ciency as well as power density compared to their permanent magnet counterparts.

Permanent magnet synchronous motors are thus gaining popularity due to high power density, compactness and current availability of power electronics needed for eff ecƟ ve control. Also, these motors are designed to be more powerful while also having a lower mass and lower moment of inerƟ a, high torque-to-current raƟ os, high power-to-weight raƟ os, and robustness.

Image Courtesy of New Energy and Fuel.com

According to an Allied Market Research, the world PMSM market is likely to generate revenue of $31.1 billion by 2022, growing at a CAGR of 10.9% from 2016 to 2022. Asia-Pacific is expected to dominate the PMSM market in terms of revenue as well as volume.

The permanent magnet synchronous motor has features of both inducƟ on motor and brushless DC motor. Like a brushless DC motor, it has a permanent magnet rotor and windings on the stator. However, the stator structure with windings resembles that of an inducƟ on motor.

Permanent magnet synchronous motor relies on magnets to turn the rotor, which spins at the same speed as the PMSM’s internal rotaƟ ng magneƟ c fi eld. They cannot run without a drive and a VFD is required to precisely control the speed of the PMSM to meet the applicaƟ on requirements for pressure, fl ow, volume, etc. Permanent magnet motor soluƟ ons thus tend to have a higher iniƟ al cost, despite recent increases in the price of permanent magnets, they are sƟ ll profi table.