Anyone know how to test motors??

Posted by Lora Knepper.

Student on team #69, HYPER, from Quincy Public Schools and The Gillette Company.

Posted on 1/6/2000 10:28 AM MST

Hi all,
I have a bit of a dilemma that I hope some you can give me a hand with. I’m a doing a sci-fair proj on the effects of spray coolant on the drill motors we use in competition. (Raul, you should be interested in any results!) However, I’m not too sure on how to test the temperature of the motors (I know a regular thermometer won’t cut it!), and the change in preformance of the motor. Please email me with any suggestions or tips! Thanks!

Lora Knepper
Driver Team 69 (HYPER)

Posted by Michael Betts.

Engineer on team #177, Bobcat Robotics, from South Windsor High School and International Fuel Cells.

Posted on 1/7/2000 12:35 PM MST

In Reply to: Anyone know how to test motors?? posted by Lora Knepper on 1/6/2000 10:28 AM MST:

Lora,

Although I have never tested a motor this way, the standard way to test big power transformers is to measure the resistance of the windings using a very sensitive micro-ohm meter. Since you can measure the resistance at a ‘known’ temperature and you know the effect of temperature on resistance in copper wire (the thermal coefficient of resistance), you can calculate the internal temperature of the windings at elevated temperatures.

To get very precise measurements, first realize that the windings will begin to cool down as soon as power is removed and you must remove power to measure resistance. Make multiple measurements at regular time intervals, plot the temperatures, fit to a curve (it will be exponential) and calculate the temperature at time zero.

Good luck!

Mike Betts, Team 177

: Hi all,
: I have a bit of a dilemma that I hope some you can give me a hand with. I’m a doing a sci-fair proj on the effects of spray coolant on the drill motors we use in competition. (Raul, you should be interested in any results!) However, I’m not too sure on how to test the temperature of the motors (I know a regular thermometer won’t cut it!), and the change in preformance of the motor. Please email me with any suggestions or tips! Thanks!

: Lora Knepper
: Driver Team 69 (HYPER)

Posted by Thomas A. Frank.

Engineer on team #121, The Islanders/Rhode Warrior, from Middletown (RI) High School and Naval Undersea Warfare Center.

Posted on 1/11/2000 6:47 PM MST

In Reply to: Re: Anyone know how to test motors?? posted by Michael Betts on 1/7/2000 12:35 PM MST:

Lora;

I would obtain some very small thermocouples, and attached one to the windings where you want to measure the temperature.

If you go to http://www.omega.com you can read all about the various types of temperature sensors available.

As for actually measuring performace, you need a dynamometer. The simplest way to make one is to use the motor under test to drive another DC permanent magnet motor (like a drill motor) as a generator…then you measure the voltage and current output from the generator under load. You also need a way to measure RPM to be really complete.

If you need more details, let me know.

Tom Frank