Electric Motor Lifetime

Interesting...how about sharing with us just one of the "many calculations" in which "motor lifetime" is used? Actuaries and others might find such information to be useful, if they don't have it already.

Motor life will almost always be determined by the life of the bearing grease used.

That's what I'd use in my calculations. Except that I know of none.

Some time ago I worked in a coal fired power station, the maintenance policy at the time was to replace motor bearings every two years with monthly greasing. I found a motor that had been "missed" in the installation records and had been in continuous service for over 25 years with no maintenance at all. The motor was covered in coal dust and dirt for most of its life. How do you calculate the motor life in those circumstances???? To me motor life depends entirely on the individual motor and manufacturing process it's impossible to have a one size fits all approach.

Generally motor life will depend up on the class of insulation, whether the motor bearings are sealed for life , duty cycle of the motor, quality of power supply, standard of maintenance, environment in which it is operating, whether the selection of motor was correct in the first place and the quality of manufacture. It is difficult to put a precise figure. In my experience an air compressor motor of 100HP running continuously 24 hours, 365 days in a year with class B insulation , with poor supply voltage conditions, good overall maintenance and clean environment needed replacement every eight years.

Motor life span? 15 seconds to 50 years plus. I've worked on plants that were built in the 30's and 40's there were numerous original motors still plodding along when I left in the late 90's. None of them working under ideal conditions.

Good question,but its the same as asking how long is a piece of string!

The answers given are very true and to the point, run life or MTBF.. Mean Time Before Failure can be "15 second to 50 years". I've been in situations where motor have lasted that "15 seconds". I worked many years ago in a steal works, they too had their own motor repair shop and were kept very busy. It ALL depends on the operation of the motor, how the motor is looked after AND maintained and is it designed for the job.

A bit silly putting in a 100HP motor when you need 200HP...

And now as awareness of "Harmonics" is at the forefront... that too plays an important part in the run life of not only motors but any other item of electrical equipment.

It is a fact of life that a motor will fail.. do you want it to fail..not really, so you try to give it longevity by following the operating and maintenance procedures.. but it will fail

So if you want to predicted a motor failure.... you could try Tarot cards, reading tea leaves or a Fortune cookie... If only it was that easy!

Actually, the question is quite simple and straightforward:

"Are there any standards, rules, recommendations or any obligations of the manufacturer's about what must be the motor life under nominal conditions?"

The answer is equally simple and straightforward:

No.

The reason for this is that attempting to predict or calculate motor life is very far from simple and straightforward, mostly due to the fact that there are far too many variations in motor types, operating conditions, application requirements, etc.

I have "Schindler" lift in my building. It was installed 70 years back it is 7.5 HP motor with high starting torque. It is still running good without even changing the windings. Of course it is well maintained. Old is Gold.

Motor failure ≈ the motor's necessity in the critical path ÷ number of alternative paths ≈ likelihood of failure

Ergo: the more critical a motor is the more likely it will let you down!

Also known as Sod's Law!

now you've offend Murphy!!

This is a good one, my cousin drives a vauxhall car around that was made in 1938, he uses it every weekend, and drives about 150 miles over two days, and he says that good maintenance and regular servicing is the key, and I expect that there are hundreds of people who have older cars in Britain, who still drive them occasionally!

Spencer.