ELANTAS and Uni Halle/Alexander Funtan
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Color-Changing Dye Sensors Detect Electric Motor Condition

May 19, 2021
A sensor system detects thermal polymer degradation in copper wire insulation.

Scientists have developed a dye process that helps detect wear-and-tear on electric motor wire insulation.

Typically, engineers can tell the condition of an electric motor by the wear on the insulation coating of its copper wires. Inside, they are usually made up of tightly wound copper wires—and these in turn are coated with an insulating resin. When the cable insulation becomes brittle due to heat and chemical processes, it may be an indicator that the motor is nearing end of life.

The trouble is that it’s not possible to tell whether the insulation inside the motor’s housing is still intact without removing the motor’s outer housing.

Scientists at Martin Luther University Halle-Wittenberg (MLU), in collaboration with ELANTAS— a division of the specialty chemicals group ALTANA— attempted to address this problem by developing an integrated dye process that allow them to detect wear on an electric motor’s cable insulation.

The copper wires inside electric motors are insulated with special resins that protect them from external influences.ELANTAS

“Until now, developers have focused on the degree to which material degrades under specific conditions,” explained Alexander Funtan, a chemist at MLU.

The next step was to develop a method for evaluating how much time would elapse before a replacement is needed. The actual wear, noted the researchers, depends on the conditions (such as temperature) under which a motor is used.

Funtan said he developed a test rig to analyze four different resin systems over several months to determine which degradation products form at different temperatures. He discovered that the four resin systems consistently released a specific alcohol under the different temperature conditions.

The dye added to the resin system changes color when an alcohol that is released by the resin binds to it.Uni Halle/Alexander Funtan

“We then worked closely with the researchers and developers at ELANTAS to find a sensor molecule for this alcohol,” he said.

The sensor molecule had to meet the following criteria:

  • The sensor molecule had to be a substance that could be easily detectable and whose properties change when the alcohol binds to it.
  • The sensor molecule needed to withstand high temperatures and normal production processes.
  • The sensor molecule could not change the insulation’s electrochemical properties.

The researchers chose a dye that normally glows reddish orange under UV light; but when alcohol binds to it, the colour spectrum shifts to a light green. The different color spectra, they explained, could then be analyzed using special devices that could be installed directly in the engine.

“This way, you can see if a replacement is necessary without having to open up the engine,” said Professor Wolfgang Binder from the Institute of Chemistry at MLU.

The researchers are hopeful the new insulation will in future mitigate unnecessary motor replacements. Potential uses for the invention include the motors of electric vehicles, as well as machines and other equipment.

ELANTAS filed a patent for the new process at the beginning of the year. The research was financed by the specialty chemicals group ALTANA and also funded by the EU’s BAT4EVER project as part of the “Horizon 2020” programme.

Check out the study: Funtan, A. et al. Self-Diagnostic Polymers – Inline Detection of Thermal Degradation of Unsaturated Poly(ester imide)s. Advanced Materials (2021). doi:10.1002/adma.202100068

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