How to Measure Life Span of DC Motor 1

[yanco]

I am working on a project to measure the life span of a DC motor in oscillating movement. The project can consist of PICmicro with LCD Display. I would like to get some ideas and the standard way to measure the life span ? Pls comments and give ideas.

 

[GusD]

Hello yanco

In reality, one cannot measure the life of an electric motor.Some motors can operate for 50 years under the right conditions ,others fail in short order due to many factors.
When purchasing an electrical motor,you can ask for a motor with bearings that have a L10 life of 40K hrs,50k or 100k hrs.This only says that 90% of the bearings used in these motors will reach the design life if all other factors of lubrication,loads or other variables that impact on motor life are met.As for the windings,
theorecticaly they can last a life time,of course most don't.
At best, you can probably say that on a particular application ,this motor should run for at least 10 years.If operating conditions are benign,this drive could last 20 years or more.

GusD

 

[Thorn3]

Hello Yanco,

GusD is completely correct.
My suggestion, would be to create a specialized scenario, where you know exactly how the motor will be used. Collect all variable data not only of the machine in question, but its working environment as well. Example: if a motor is to sink "X" amount of thermal energy to the ambient air, the higher the ambient air temperature, the less thermal transfer will occure, possibly causing premature failure in the windings. In that scenario, it would be wise to program a PIC type circuit to measure the motor temp and compare it to ambient air temp. Of course employ the typical voltage and current measures. Vibration measure etc. What you choose to analyse fully depends on the operating conditions of the motor, its load and its environment. If you can cut down the amount of factors needed per application, you can determine a rate of failure more easily and employ a sensor type circuit to observe and warn of possible failure conditions.
So, first you must know the normal operation data of the specific motor. Then, you must know the working load and environment. From this data, you can construct an observation tool that could possibly determine what it is that you wish to know.
You chose an exceptionaly difficult task. I hope this helps you. Also keep in mind that this tool would only be useful in determining when, under what conditions, a certain motor should be changed or checked/repaired. It is purely ballpark.

 

[RadarRay]

Just a note, in the 70's, the GE Kinematics manual for DC motors included life charts for the Field windings of their shunt wound DC motors. The life expectancy was well known when under rated field conditions. This in part is why field economizing was developed. To increase the life of the motor.
What is interesting, is if I could find one of my old copies, I wonder if the data is still valid, considering how the manufacturing process has probably changed over the years.

 

[jbartos]

Suggestion: Usually, manufacturers and their representatives have the life expectancy of motors in various applications available.