The next generation of electric motors

The motor control methods developed by Asad Awan make the new kind of electric motor a serious contender to the cage induction motors dominating the market today.

– Nearly half of the electricity produced in the EU is spent in electric motors, says Asad Awan from ABB to introduce his dissertation.

Even a slight increase in efficiency would therefore mean significant savings in energy consumption. The most promising competitor to the traditional cage induction motor is the synchronous reluctance motor.

The most promising competitor to the traditional cage induction motor is the synchronous reluctance motor.

– It is smaller in size and induces less dissipation than cage induction motors, says Awan.

In light of this, it is no wonder that the selectors of the 2020 doctoral thesis award at Academic Engineers and Architects in Finland TEK and TFiF Tekniska föreningen i Finland chose to highlight Awan’s dissertation as the best from a group of 30 high-quality candidates.

”The reluctance motor Awan discusses in his dissertation would be a terrific option for industry as its manufacturing costs are competitive with cage induction motors, it results in significantly smaller energy losses than cage induction motors and its manufacturing does not require rare earth metals”, said the jury in justification of their choice.

An old invention that is difficult to adjust

As an invention, the new kind of motor is not that new: the principle was first presented in 1923. However, we had to wait nearly 90 years for the first commercial application. ABB introduced its first synchronous reluctance motor in 2012.

The explanation for the long road to commercialisation is simple.

The synchronous reluctance motor does not turn on automatically when connected to alternating current. It requires the help of a frequency converter that allows the user to adjust the current fed into the motor and its frequency. This technology was only first utilised in the Helsinki Metro in the 1980s.

Since then the frequency converter technology has rapidly become more common in controlling cage induction motors. 

Synchronous reluctance motors, however, require a special control method of their own.

– Adjusting the motor is extremely difficult, Asad Awan says.

These control methods are exactly what Awan discusses in his dissertation.

For industrial use and electric cars

The benefits of synchronous motors are indisputable. In industrial use their most significant benefit is the improved efficiency when compared to cage induction motors.

In pump and conveyor motors that run 24/7, an improvement of a couple of percentage points could mean annual savings of hundreds or thousands of euros. Car manufacturers are also attracted by the motor’s small size, good torsion at low RPM and the possibility for high rotation speeds.

The features of the motor can be customised by adding permanent magnets. For example, the electric car manufacturer Tesla replaced their cage induction motors with permanent-magnet synchronous motors in their latest Model 3s.

However, there are some obstacles to their popularisation.

For the synchronous reluctance motors to become more mainstream, they should be able to function without speed and motion sensors like the current cage induction motors do. It should also be possible to freely mix and match frequency converters and motors from different manufacturers.

The software controlling the motor should also be able to automatically recognise the features of the motor connected to it and adjust itself automatically to suit the motor.

This is exactly what Asad Awan’s dissertation tackles. At the core of the work is a piece of software that enables the control of different synchronous reluctance and permanent magnet motors.

– This is the perfect package. It recognises the features of the motor and controls it effectively, Awan says.

This is the perfect package. It recognises the features of the motor and controls it effectively.

The methods discussed in the dissertation are useful in both industrial uses and vehicle motors. 

Of the six research papers that the doctoral thesis consists of, Awan’s personal favourite is the one on the plug-and-play method he developed to start synchronous motors. IEEE Industry Applications Society chose that paper as the best research article of 2018 on electric motor drives.

– You only need the basic information about the motor, its operating voltage and output.

With this information, Awan’s algorithm recognises the magnetic properties of the motor connected to the frequency converter and says how it needs to be adjusted. 

As they are, the methods would be suitable for controlling the motors of the new Model 3 Tesla, for example.  

Real-time adjustment

The first two research papers of Awan’s thesis present a new kind of mathematical model for adjusting the current of synchronous reluctance motors. It is especially useful in high-speed vehicle motors.

The adjustment algorithm runs without sensors and calculates the electromagnetic state of the motor and the position of its rotor in real time. Based on this information, the frequency converter controlling the motor adjusts the current up to thousands of times per second to maintain the speed of rotation and moment at exactly the desired levels.

Awan completed his dissertation in a research group on electric drives headed by Professor Marko Hinkkanen. The real-time adjustment of power electronics and mathematical estimation are the group’s top strengths.

Developments in power electronics have allowed the new motor type to enter the market. The challenge faced by researchers is how to control it as intelligently as possible.

One must be very familiar with the physics. Everything is based on physical models of the controlled motor.

– One must be very familiar with the physics. Everything is based on physical models of the controlled motor, says Professor Hinkkanen, who supervised Awan’s work. 

Asad Awan joined Hinkkanen’s group for a summer job in 2014. After joining the group, both Awan’s master’s thesis and doctoral dissertation were completed at a rapid pace. In the fall of 2019, the freshly minted doctor transferred to the payroll of ABB who were funding the group’s research.

– Asad Awan was really hard-working and motivated – and quick to learn. His dissertation was easy to supervise, Hinkkanen recalls.

The Professor is not sad to see the award-winning thesis author moving from academia to industry.

– That is our goal, he states.