Our robust electric machines backed by in-depth performance engineering

Looking for high-speed electric or large permanent magnet machines with top performance reliability?

You can count on The Switch. Robust performance is our top priority.

Our permanent magnet machines weigh up to more than 50 metric tons. Torques in our large shaft generators and propulsion motors can reach more than one million newton-meters, equal to the torque of 4,000 average family cars. And even with these enormous weights and torques, our machines run dependably fortheir entire lifetime in demanding environments.

Let’s briefly take a look at the rigorous performance engineering each of our products undergoes before finally arriving for installation in your vessel.

Electromagnetic considerations

Not surprisingly, electromagnetic engineering is the design starting point with electric machines. During the electromagnetic engineering process, we engineer all the key performance parameters of the machine. The machine is electromagnetically designed to produce the needed torque and power at all the desired operating points. Also, we optimize the efficiency of the machine and evaluate loss distribution between different components. Efficiency optimization helps reduce the total cost of ownership as well as the environmental cost.

Typically, efficiencies in well-designed electric machines vary between 93-98% depending on the operating point and the design of the machine. This means that 93-98% of the mechanical torque is converted into electricity (generator) or vice versa (motor) and the rest is transformed into heat. In a typical shaft generator, one percentage point increase in efficiency can avoid annual GHG emissions equivalent to roughly 20 passenger cars and save approximately EUR 20,000 from reduced fuel consumption.

Thermal considerations

Even losses of a few percent are a significant source of heat for multimegawatt machines. To give an example, for a 2MW machine operating at 97% efficiency, heat losses are equal to 10 electric sauna stoves all constantly pushing heat into the machine.

Because of the significance of heat losses, the thermal engineering of large electric machines is of utmost importance. Sophisticated thermal calculations are needed to make sure that the machine is kept cool as effectively and uniformly as possible. Temperatures at the stator windings must be kept below the limits allowed for the particular insulation system, and temperatures at the permanent magnets kept sufficiently low to guarantee long, reliable operation of the machine. 

Structural considerations

It is easy to acknowledge the importance of electromagnetic and thermal engineering of electric machines. The importance of structural engineering, however, may sometimes be forgotten. After all, there is only one moving part, the rotor. Still, structural engineering plays an important role when designing  a reliable electric machine.

Extensive structural analyses and simulations are required to ensure safety, reliability and smooth operation. This applies whether we are discussing high-speed machines with immense centrifugal forces affecting the rotor or large permanent magnet machines with enormous torque putting stresses on structural components.

Safety aspects arise when considering structural integrity during the machine operation and also in different handling and lifting situations. No risks can be taken when designing safe lifting points for machine assemblies with masses up to 100 metric tons!

Electric machines must operate reliably for tens of years while withstanding significant external and internal loads. It is not enough that the machine withstands certain set of static loads. It also needs to withstand different varying loads, such as inertial loads induced by the rough seas, repeating changes in rotational speed and torque, not to mention external vibrations from the environment.

From the earliest design phase, we use structural analyses and simulations to identify possible structural weaknesses so that potential sites for fatigue failure can be eliminated.

In the structural analysis and simulation phase, we also verify smooth, low vibration operation of the machines and their components. Uncontrolled vibrations can lead to excessive noise and reduce a machine’s lifetime. Each machine and its components must be designed with enough stiffness to avoid critical structural resonances. Sufficient system stiffness also ensures that internal excitations remain at low levels.

We always make sure load bearing structures are properly optimized for the known load conditions. Using materials in exactly the right quantity and location minimizes the weight of the machine and its environmental footprint without compromising structural integrity.

Simulations and analyses

We conduct structural simulations with state-of-the-art analysis software, such as Ansys engineering simulation software. Our in-depth analyses include such techniques as advanced finite element analysis (FEA).

For the design of new products or product families, we carry out vigorous analyses and simulations. In addition, for each machine ordered from our existing product platform, the project’s lead engineer together with structural engineering specialists thoroughly assess

the need for any structural analysis for the particular project.

We are painstakingly thorough, for when it comes to structural integrity, attention to every detail is essential. We pay special attention to load bearing welds and other connections, systematically analyzing the fatigue strength of welds and optimizing other structural details to minimize the risk of field failures. Stresses and stress variations in critical areas with their expected load profiles are accurately predicted with finite element analysis. Thereafter, we use appropriate assessment methods to verify that stress variations remain sufficiently low so that fatigue failures do not occur.

To look at vibrations, we start witha modal analysis of the system to find out the most significant natural frequencies. Natural frequencies are then compared to known excitation frequencies. Finally, the structural stiffness of the machine or a component is fine-tuned to avoid detrimental resonances leading to elevated vibrations. We often also conduct response analysis – harmonic or transient – to verify that the vibration response of the machine is acceptable under different operating conditions.

The structural engineering phase can take from weeks to several months, depending on the machine type. Completely new concepts require more extensive analyses to make sure that all design details are studied appropriately.

Finally, we use the results of our structural simulations and analyses to develop a finely tuned machine structure, featuring optimized

  • Component shapes
  • Material thicknesses
  • Material grades
  • Structural details
  • Weld sizes
  • Number of bolts and other mounting elements

And much more.

Enthusiastic team

The Switch used to outsource more of its performance engineering. Today, performance engineering has become more integrated into the design process of our machines.

All team members have either a Master or Doctor of Science, an interest in physics, an enthusiasm for complex problems and a highly systematic way of thinking.

Robust designs

At The Switch, we prioritize reliability and robustness of design.

As a result, we have very high standards for analysis processes. We put lots of effort into structural, thermal and electromagnetic simulations and analyses to make sure our customers get reliable, efficient machines.

And the results of making performance such a high priority? As an example, we have about 150 shaft generators in operation with several million cumulative operating hours since 2015 with zero failures that would have led to a vessel’s downtime.

If you’d like to further discuss our processes or any other aspect of our performance engineering, don’t hesitate to get in touch. We are always pleased to talk about the details.

Manager, Performance Engineering

Toni Kilpeläinen

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Toni Kilpeläinen currently works as Manager for Performance Engineering – Electric Machines at The Switch. He has over ten years of experience in the structural engineering of rotating machines, including wind and marine PM generators and high-speed electric machines. Today, his main responsibilities include leading the performance engineering team, performing structural analyses and simulations, developing analysis methods and tools and coordinating outsourced engineering analyses. Kilpeläinen holds a Master of Science degree in Mechanical Engineering from Tampere University of Technology.