Company B’s Motor Design Process

CoB’s product portfolio is readily planned and the machine diameters to be designed in the future are already chosen. This is made to limit the product variations. The mechanical inter-faces are defined by SAE –standardized flanges that are widely used in automotive and mobile work machine industries. The rotational speed offering of each frame size is mainly defined by the rotational speeds of combustion engines used in the actual applications.

The goal of CoB’s product strategy is to change the existing offering as little as possible.

Changes to the offering are requested rarely and most often the requested changes are related to minor details of the design like the geometry of the shaft, or the fixing interface of the ma-chine. Because CoB has predefined offering, it is easy to choose a fitting machine for each customer. If the existing machines do not fill the requirements, customer’s business case is

evaluated and based on it a decision of designing a new machine is made. Machines are not designed for a single customer, if the volume expectations of the market are too low.

The machine specifications are mainly determined by CoB according to the needs of the mar-ket. Some minor details and mechanical interfaces can be modified according to the custom-er’s specification, but the machines themselves are determined by fixed offering.

The whole new product design project takes normally under half a year. Some projects are of course longer than others as every project is unique. The rapid pace of the NPD project is ex-plained partially by the fact that the technology used in the machines is pretty much identical.

For example the pole structure and stator winding variants stay the same; the machines are on-ly scaled to match the power requirements and flange dimensions.

The designing itself starts from the torque from which the dimensions of the active parts can be calculated. Mechanical design of the frame starts immediately after the electrical designer gives the first rough estimates about the machine’s diameters and stack length. Unlike CoA, CoB does not design gearboxes to its machines by default and thus the design procedure re-minds closely that of KONE. Designing the active parts takes roughly one month and same applies also to the mechanics. During the mechanical designing phase the necessary iterations to the electrical design are made. Mechanical design is started by studying if the new frame can be casted and if current subcontractors can manufacture such castings. In some cases the supply chain needs to be enlarged and possible new subcontractors evaluated.

The calculation procedures and algorithms that CoB uses have been proven to be quite accu-rate and the calculated maximum torques and efficiencies seem to match the actual values well already in the first prototypes. Normally one prototype round is enough for a machine with new frame size and no major changes are needed. The space reserved for the stator end-windings is quite commonly either too small or too big in the first prototype and needs to be changed for production.

CoB’s machines are liquid cooled and normally they are a part of the diesel engines cooling circulation in a vehicle. The flow calculations related to the design of liquid cooling are made by a subcontractor that is specialized in FEM -modeling of flow- and thermal systems. Be-cause the service received from the subcontractor has been high quality, CoB has not seen it necessary to start developing own competence in thermal modeling.

After the design phase has been completed, it takes some 2-3 months to get the first proto-types. The prototypes are shipped to the customer straight after they have been tested to match the specifications. The customer then tests the machine in its real application and environment.

Design changes are made on the base of customer feedback and second batch of prototypes is ordered after this testing period. CoB has also a demonstration setup for application testing in its premises. The power of different parts of the setup can be measured and based on the measurement the benefits of the solution can be evaluated. The same setup can be used to demonstrate bigger and smaller applications as the results can be scaled to appropriate level to match those of the customer’s application.

After the possible second prototype round the design is finalized and moved directly into pro-duction. CoB’s design process is presented in Figure 3.8 as interpreted on the basis of the in-terview.

Figure 3.8. Company B’s electrical machine design process

The product changes are done by the R&D team as a regular design project because there is no PCM specific organization to take care of it. If there occurs some problems with the existing design and the root cause of the problems is identified to be the actual product design, the product changes are made by adding a new revision of the design to CoB’s PDM system.