Today, however, we have materials that make the three-phase direct drive system effective. The most important of these are high-performance magnets and silicon semiconductors. They made it possible for Jöckel to simply build the motor around the axis — an approach that he believes is the most obvious one. “Even a child can see that the drive system for two wheels should be built on the axis between them,” he says. The direct drive system works in the simplest way imaginable: the rotor and the stator are concentrically arranged around the axle. The electromagnetically generated torque is strong enough to drive the wheel set directly — which was not the case a century ago. Everything that has been developed in the meantime to make the motor’s work easier — in other words, the transmission, the rods, and the clutch — is unnecessary. A prototype is already traveling the Munich subway system. In this initial phase it’s operating without passengers on its nightly test drives. However, starting in January 2008 it will be used in normal subway operations.

Jöckel is convinced of the effectiveness of his invention because of the simplicity of the direct drive system. Because it lacks all of the components normally used for transmitting power, the cost of maintenance is much lower than for conventional traction drive systems, which are extremely complex. Besides, as a result of this simple structure the drive system can be completely integrated into the bogie, so that it does not need its own bearing, for example.

Another synergy leads to simplification of the braking system. Today’s rail vehicles have two redundant braking systems on board: an electrodynamic one and a mechanical one. The permanent-magnet direct drive system makes them unnecessary, because with the electrodynamic service brake system the electric motor operates as a generator, transforming the mechanical energy into electrical energy, and feeding it back into the network. Today, if the electronic braking system malfunctions, the mechanical friction brake takes over. By contrast, the service brake system in the permanent-magnet machine works even when the power network or the electronic system is defective. In this case, the energy is stored directly on resistors, which makes the braking system inherently safe. As a result, the friction-based brake will soon be a thing of the past — and together with it a large number of complex and maintenance-intensive components will become obsolete.

Even when he was a child, Jöckel’s favorite activity was tinkering with motors — preferably the motors of model planes. Since then, his interests haven’t changed a bit. In combination with the inventions of his colleagues, the direct drive system has developed into a highly integrated motor bogie called Syntegra, which looks set to lead to a generation change in rail vehicle drive systems. Combined with the inherent electrodynamic brake (IED) described above and a new kind of compact, lightweight bogie (see Inventor of the Year 2007, Martin Teichmann from Siemens Transportation Systems in Austria), a new type of rail vehicle was born.

Jöckel has already received 72 patents and is responsible for 23 inventions. He’s still primarily interested in motors, even though he’s now working in another location. He recently moved to Loher GmbH in Ruhstorf near Passau, a company that is part of Siemens Automation and Drives, where he is developing special drive system solutions for special applications such as ships and wind turbines. “Here I can once again give my passion for experimentation free rein,” he says.

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