Motor temperature measurement 1

[solocam92]

Does anyone know a way to measure the armature temperature of a PM DC motor without having to stop the motor? Reading the resistance between two leads requires the motor to be momentarily stopped which I have to avoid. I've been experimenting with thermocouple&thermistors and a Mercotac slip ring but it hasn't produced accurate results and is a bit of a challenge to setup.

 

[btrueblood]

Put a battery operated circuit on the motor shaft? This could be a simple logger that you download periodically, or an RC or IR wireless transmitter to get the data in real time.

 

[Strong]

Depending on size of motor, you could consider a wireless telemetry system, such as from Binsfeld. Another way might be noncontact with an infrared sensor, such as from Exergen.

Walt

 

[lukin1977]

If you can see the armature while in operation you can use an infrared gun

 

[solocam92]

Thanks for the responses.

I have tried to use an IR sensor but did not have good success. The surfaces of the armature that I am able to see have too low of an emissivity.

I looked into the wireless system a bit, and it looks promising. I've never used one before, so any additional information that you think I should know would be appreciated. The smallest motor is 0.01 hp so a circuit would have to be quite small (less than 1 in^2).

 

[btrueblood]

FWIW, the typical safety test for motors involves measuring the "locked rotor" maximum temperature and comparing the resulting temperature rise to the rotor winding insulation max. rated temperature.

 

[crshears]

I remember from some years back that certain of the thermal generating units I helped operate had special meters connected into the field circuit that divided the applied field voltage by the field current to get resistance; and since conductor resistance is proportional to temperature, the gauge was calibrated to read generator rotor temperature directly in degrees Celsius.

Would something like this be adaptable to your application?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[solocam92]

crshears- Was that method used for a permanent magnet DC motor? It seems to me that something like that would work on a brushless DC motor or AC motor but not PM motor.

 

[crshears]

Hey solocam92, I may have gone down the wrong rabbit hole on this one; I saw "armature" and thought wound, rotating component connected with either sliprings or brushes. Sorry about that.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]