Motor Failures

Heat is the motor's enemy.

See that it is not overheated.

Google "electrical motor care" and read.

Thanks

set up weekly starter contact inspection & manintainence, check loose connections in motor wiring ,use a blower to clean dust, check motor overload trip settings, these actions will minimize motor failure and burn out Chances by 98% & Pray god you wont have motor burn oust

I would also add check and record the temparature while running. And if there are other bearings in the system(fans, etc.), check those as well for running temperature as they may cause a motor failure if they fail. I do this monthly on plant/equipment exhaust systems and haven't had a failure in over 15 years. The "downstream" temperatures alert you to possible upcoming failures and then you can schedule the appropriate maintenance.

Make sure that the overload protective device installed downstream of the circuit protective device is set to the same full load amps as shown on the rating plate on the motor.

Thanks

British Standard 7671, again, gives full protocols for co-ordination of motor- and circuit-protection devices.

In installing and setting motor overload protective devices, the check is applied continually while power is applied to the motor.

As Lyn said, you need to reduce the heat. That may not be a function of the current per se. A clogged air-vent may be the cause, in which case an overload relay may not be adequate. Embedded thermistors may be a better option.

Does it mean that when we are procuring new motor ,we have to specify that it should consist of embedded thermisters also?

As only one motor has been procured for the said application,do we have to procure a spare motor or periodical check up of the motor temp.,load etc would be sufficient?

Embedded thermistors make the motor expensive. While this is a technically superior method, economics don't always justify it. The best is to know the required load and select a motor with an adequate factor of safety. Good maintenance can take care of heat build-up due to clogged airways and such avoidable failure modes, minimizing the need for thermistors or such expensive protectors.

Thanks

Buy a spare motor!!!!!!

Repeat,

Buy a spare motor!!!!!!

You have no experience with electric motors, so the odds are high that one will fail.

As you have rightly pointed out that experience counts, I had also suggested to procure a new spare motor to take care of any eventuality.As prevention is better than cure,useful suggestions have been invited for daily monitoring to avoid breakdowns.

Always a good policy in any event. If you have a motor that is critical to production, always have a spare on hand(unless of course you can talk your local supplier into doing it for you-at no cost). I have spares for every motor in my plant as well as other "critical" parts, just in case. It costs a little up front, but can save much more in lost down time than you realize. You may have to analyze what the cost of down time would be, and then justify the capital cost to the boss on expensive parts.

I know I have said this before in other threads. Reference - 10 amp fuses.

Dear Mr.pokalasaro,

1. Use single phase preventer, to avoid running on 2 phase.

2. Select correct type of Grade of Insulation to suit Temperature Rise and Thermal relay should be set properly. Ensure proper ventilation is maintained.

3. If VFD application, use Motor suitable for VFD application and ensure seperate blower for cooling the motor. This is very essential when the speed of the motor is around 1/5 of rated speed where the air circulation over the mototr is practically nil to remove the liberated heat.

4. For vfd motor, the heat liberated due to harmonics effect should be less than 6% of the capacity of the motor in KW, and the harmonic filters should ensure this.

5. Keep the motor surface clean to facilitate proper dissipation of heat.

6. For frequent on-of duty condition, select right type of motor for example for crane it should be Class S1 duty.

DHAYANANDHAN. S

Use correctly rated over load protection

Timely preventive maintenance of Switches and Contractors to be carried out. All connecting points should be regularly checked for loose contact during preventive maintenance. For three phase motors install single phase preventer. Properly rated motors should be used .Over loading and over heating should be periodically checked .

Depends on selection,installation,ambient,power quality,protections, maintenance, condition monitoring etc

I used to slavishly follow PM schedules while in the RN, I am not of the opinion that it prevented any real failures though.....I personally feel that phase monitoring, temperature monitoring and stall monitoring would be better, particularly temperature....

As many have already stated here, heat is what must be monitored. It is caused by most if not all the usual motor faults for single phase, 3 phase, even DC motors.....even mechanical problems of bearings and too much load.....or capacitor damage, or phase loss.......in fact as I said before, most if not all faults.

(I cannot think of a fault that allows a motor to stay cool personally, except maybe if it gets flooded with cold water!!)

I do not understand why having a "built-in" thermistor is so expensive, but I believe you when you say that!! It looks like the motor manufacturers DON'T want you to keep the motors "safe"!! They want you to simply buy more!!!

How about a simple, external, clamped on thermistor? Remote temperature monitoring? Many are made for monitoring pipe temperature, quite cheaply, like this one:-

At:-

pipe-clamp-temperature-probe-thermistor

Or even make your own. Naturally it won't be as good or as fast as a built in one, but it could show "trends", which is what you mostly need anyway...

In my experience, motor overheating is usually not "sudden", it takes place over a specific time frame. Except maybe a phase loss on a 3 phase motor is faster, but its usually easy to monitor the 3 phases and power the motor down if one is lost.....

Use that special PC CPU grease to transfer the heat to the sensor well, and clamp it mechanically on a clean bit of the casing!

Of course some sort of automatic monitoring would be best of all, an interface that allows almost instant monitoring of all the motors, with alarms shown when the usual running temperature is exceeded for any reason and by how much.

Properly implemented, it should allow a motor to be simply monitored and any changes that need to be investigated, to be done at a planned time, instead of interrupting production.....

It should over a few years, more than pay for itself in reduced unplanned downtime alone....

But I am pretty sure that it is not anything new, I would expect it to have been installed many times worldwide, you maybe need to find the right person/company....

As you did not give us any idea of how many motors and the distances concerned, its difficult to be more precise.....

Remote monitoring usually costs more, local monitoring needs a watchman to check the monitor say every 4 hours.....also expensive......

But please remember, all of the above are just my thoughts and my opinion only!! But I hope it gives you some ideas and direction....best of luck!!

Pokalasrao,

• What are the motor specifications?
• What type of atmosphere is it installed in? Wet? Dusty? inside? outside?
• Though most motors need the same type of PM, Larger HP motors really need to be aligned correctly.
• Have you taken vibration readings on the motor?

There are so many things that can affect a motor and it's life span, please fill in the blanks and we will do our best to assist you!

Thanks to one and all for their views and suggestions which are really helpful.

Do not over grease the motor, I have opened many motors that were full off grease.

Very good point, learn a little about tribology.

As previously stated,heat is the number one enemy of an electric motor.

Heat damage is accumulative.

Cooling an overheated motor does not heal it,it just prevents further damage.

The causes of excessive heat are many,including mechanical overload,due to a failing

bearing in the motor or the load,ambient temperature,loose connections anywhere in

the power circuit,improperly selected and installed thermal overloads,excessive

voltage drop due to undersized conductors,misalignment of motor and load

shafts,excessive tension on belt drives or conveyors,or improper selection of motor

for the load.

Predictive maintenance has now replaced preventative maintenance,and there are

many ways to predict failure.

Ultrasonic monitoring can give very good information on bearing condition,infrared

scanning can detect hot spots due to loose connections in wiring,overheated bearings

and motors.

There is a learning curve when listening to a bearing to separate the normal sounds

from pending future problem sounds.Even new bearings are noisy in the ultrasonic

range,but a failing bearing gives a unique signature depending on which part of the

bearing is failing,whether it be wear on the races,excessive clearances

developing,lack of lubricant,loose press-fits,and many others.

There are some expensive ultrasonic devices that are very sophisticated and do the

work for you,and allow a layman to get good results.

I highly recommend an ultrasonic and infrared scanner.

Scanning on a daily basis in overkill,IMHO,and weekly or monthly will suffice for most conditions.

Preventing a motor failure is impossible,because motors will eventually fail.

I have only seen one type of virtually "immortal motor",and it ran fully immersed in

oil for cooling and lubrication.

The best one can do is to prevent a failure during critical times and schedule

corrective,preventive action during a scheduled maintenance window.

Appreciate good suggestion.

Heat has been mentioned many times already here by several others as well before this excellent post.

Heat is the best indicator. Its that simple.

Got it now?