How Do You Conduct Temperature Rise Test On Brushless Dc Motor?
Place the test motor in the rack and lock the shaft. For brushless DC motors, direct the wires from the switch and under the ball bearings outward to measure the winding resistance to avoid errors introduced by the brushes and contact drop. Measure the resistance of the cold wind with a multimeter and record the ambient temperature. Attach the thermocouple to the shell to control the temperature rise. Attach the motor terminals to the programmable power supply. Then, slowly increase the voltage until the rated current is reached. Keep the rated current for 1 hour after the case temperature levels. Quickly disconnect the motor terminals and take the resistance of the hot winding with a multimeter. Record the ambient temperature.
At least, this is how I conduct temperature rise for my 48V BLDC motor.
The most likely thing to be overheated is the wire insulation, so the winding resistance is used to measure temperature rise, as this gives the wire temperature. There may be a long time constant between external case temperature and the temperature of the wires. The wire material is needed to calculate temperature rise, though most likely it will be copper wire. The thermal time constant is useful, but most small motors will reach a stable temperature in 30 minutes or so. The current rating should be adhered to, otherwise you may find out it is overheating after damage is caused. If you don’t have that, it can be estimated from the wire diameter with de-rating, or make an initial test after one minute or less if in doubt. Note that certain permanent magnets can be overheated but the wire is more likely to overheat.
