Small clever wedge improves performance – and saves money

A wedge measuring just a few millimetres could save the Volvo Group a great deal of money. Maddalena Cirani, an engineer at the Volvo Group Trucks Technology, has discovered a straightforward and effective way of reducing the number of expensive components in the electric motor, while maintaining machine performance. Her idea is now protected by a patent.


Maddalena Cirani works at the Electromobility and Subsystems Department. This department has been tasked, among other things, with developing and testing different technologies for hybrid and electric vehicles.

In 2009, she was asked to take a closer look at and develop the department’s knowledge of electric motors. This has now led to a Volvo-owned patent on her idea and the opportunity to design her own electric motor which could be tested in different vehicles within the Volvo Group.
“It’s fantastic! I really love the idea of developing good products that will help to benefit the environment. This will have a positive environmental effect, as a reduction in cost would make electric vehicles more accessible. It will also help the Volvo Group to save money,” she says.

Maddalena Cirani’s idea is based on magnets. They are important and essential components when it comes to making an electric motor compact and produce high torque and a high level of efficiency. At the same time, they contain special, expensive substances and, together with the high cost of batteries, this helps to make the technology associated with hybrids and clean electric vehicles very costly compared with the traditional diesel solutions. 

In electric motors for vehicles, these magnets are often embedded under a film of iron in the moving part known as the rotor. However, an ineffective leakage in the iron prevents the magnet from being fully utilised.

“This makes the electric motor unnecessarily expensive,” says Maddalena and she goes on to explain that her aim was to find a way of stopping the leak, thereby saving money.

The solution was a small wedge, no larger than a thumbnail, made of composite material, which is inserted in the area around the magnet.
“I spent a lot of time thinking about ways of stopping the leak and I came up with the idea of using a wedge made of a non- magnetic material of high strength. I chose composite material for the wedge, which would prevent the leakage and at the same time fix the whole structure of the mechanical rotor in place,” explains Maddalena Cirani and tips a pile of small wedges of different colours onto the table in front of her.

“During the spring, I worked on developing the shape of the wedges to obtain the optimal result,” she adds.

To demonstrate her idea, Maddalena took one of the best electric motors on the market and inserted the wedges. It emerged that the weight of the magnets in this engine could be reduced by 41 per cent and that the motor would still produce the same performance as one without wedges.

She has worked out that, with production of 10,000 machines, the cost of magnets could be reduced by more than US 1 million.

Work on designing a new engine with wedges is now continuing and the target is to produce and test the new design both in a laboratory setting and in vehicles.

“I am really looking forward to continuing to test this concept,” says Maddalena Cirani.


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  1. Well done Maddalena, greta achievement, congratulations.