Monitoring permanent-magnet motor heating with phosphor thermometry

The fiber-optic-conveyed, laser-induced fluorescence of a thermographic phosphor was used to measure the surface temperature of the rotor in an operating permanent-magnet motor. The technique uses a pulsed laser to interrogate a surface-bonded film of europium-doped lanthanum oxysulfide for the purpose of determining its temperature-dependent, exponential-decay lifetime. By using digital-delay circuitry to control the measurement systems timing, the authors achieved spatial resolutions of better than 2 mm at speeds of up to 700 rotations/s. The precision of the temperature measurements was 0.3°C. The details of the measurement system are presented and discussed