Going up — Software tackles thermal, EMC problems for elevator maker

To reduce complexity, designers divided critical components into slices for such tasks as air-flow analysis.

To reduce complexity, designers divided critical components into slices for such tasks as air-flow analysis.


The Pro/E model shows the variable-frequency drive design from Dube's team. It boasts EMC filtering and inductive-line coupling.

The Pro/E model shows the variable-frequency drive design from Dube's team. It boasts EMC filtering and inductive-line coupling.


The software makes it possible to specify components such as large heat sinks for variable-frequency drives earlier than possible with ordinary methods.

FloTherm and FloEMC software, from Flomerics Inc., Marlborough, Mass., handle the analysis for Otis Elevator Co., Farmington, Conn. The problem Otis faces with sequential analyses of thermal and EMC is that thermal properties and electromagnetic compatibility are like rival siblings: Try to please one and the other complains. To make matters worse, regulations in the European Community make design for electromagnetic compatibility (EMC) more challenging. "Elevator drives there must meet separate regulations for emissions and susceptibility," says Otis Principal Mechanical Engineer Randy Dube. Variable-frequency drives turn the lift motor into a generator when an empty elevator car moves up and when a full car moves down, thereby putting power back into the grid and reducing energy costs.

The software used a subset of the drive geometry for the thermal and EMC models. The team designing the drive considered effects of location, number, size, and type of openings on radiated emissions. Noise, thermal, and EMC requirements interact with each other to make it more difficult to meet requirements. For example, putting more vents in the enclosure to improve cooling lets the drive radiate more EMC and acoustic noise.

Designers analyzed ideas for improving thermal and EMC conditions in the thermal-EMC software. This helped them make small changes in vent locations while simultaneously determining their impact on thermal performance and EMC. A more detailed model helped the team assess problems such as heat sinks that act as antennas and box-structure resonances that contributed to electro-magnetic interference. In the end, the prototype performed as the simulations predicted. "We met all thermal and nearly all EMC requirements on the first iteration," says Dube.

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