Electric motor overheating

Re: Electric motor overheating

Dustmaker Mike

Could be something simple like saw dust blocking the cooling air flow. What are these small motors doing?

6 reasons  *LINK*


https://www.groschopp.com/blog/6-reasons-your-motor-is-overheating/

Plus one more

Keith Newton

If a bearing / bushing in it or whatever its powering has worn out or too dry, the extra load required makes it now overloaded.

Re: Electric motor overheating

John McGaw

Hard to tell from your post. Are you saying that you have more than one motor that is suffering from the same problem or is there just the one?

I'll add one more possibility to what others have offered: it is entirely possible that the thermal protection is, itself, defective and tripping at a lower-than-desired temperature. Do you have a way to measure (safely!) the actual temperature of the motor's innards?

Re: Electric motor overheating

Kneale Brownson

Motor gets too hot to keep hands in contact.

Didn't take high altitude into consideration. We're at 10,000 feet above sea level. But we've had motors overheat at 660 feet above sea level too.

Motors are running knitting machines.

The overheat protection system on this type of motor has been replaced in a couple cases by replaceable fuse holders/fuses. An electric motor technician did the first one for us, I did the second after he passed away.

These are European motors on European machines that have not been produced since the companies went out of business years ago.

Re: Electric motor overheating

John K Jordan

Low supply voltage can also cause an electric motor to overheat since the motor will try to pull more amperage to maintain the load. In a facility with multiple motors the voltage to just one can still be low due to several reasons.

JKJ

That was reason number 4

Re: Electric motor overheating

Kneale Brownson

Wiring was done with multiple motors planned.

Don't forget the line frequency

Dustmaker Mike

Are these motor 60 HZ or 50 HZ. That will over heat them fast because the reactantance goes up. Similar to resistance but caused by the frequency. Also there is a lot of lint that might be blocking the vents

Are they continuous duty motors?

Re: Electric motor overheating

GolfSteve

Do the motors run at full speed or are they controlled by variable speed drives?

Operation at low speed (with shaft mounted cooling fan) can cause overheating. In this case forced draft auxiallry cooling fans can be required.

Many motors operate at a temperature that is uncomfortable to touch (60 to 80 deg C). The thermal overload needs to be set based on the motors nameplate rating.

Thermal overloads also wear out. I’ve had to replace a number of them over the years (in heavy industrial use).

Re: Don't forget the line frequency

Kneale Brownson

60

Yes

Re: Electric motor overheating

Keith Newton

I think he meant that at that altitude, the thinner air may not be thick enough to take the heat away.

The first thing I would try, is to sit another fan blowing onto the motor. Also, paint it black if it is a light color. Flat black will give off radiant heat.

You might also google, aftermarket electric motor cooling fins which will help dissipate the heat.

Other considerations might be the weight or stiffness of materials being run putting a lot of drag on the works.

Re: Electric motor overheating

Kneale Brownson

Motors spin a gear that drives a belt. When the belt reaches an adjustable range of travel, the electrics reverse and the motor to send a fixture on the belt back

Re: Electric motor overheating

Pete in Holland MI

If your machine was built to run in Europe, it was designed for 50 Hz electricity. We have 60 Hz here in North America. Most motors will run at either frequency, but a machine designed to run at a certain speed at 50 Hz, will be running 15% or so faster on 60 Hz. Is the load on the motor at this speed absorbing more power than the motor can handle?

Twas kinda mentioned earlier, but if the wire sizes to run the motors, all the way from where the power enters your building, are not big enough and will cause a motor to run hot. This includes size of breaker, wire thru the whole system up to the outlet, extension cord (usually the culpret), size of the cord out of the machine, and from that point, thru the machine up to the motor. Any heat being generated on any of these wires can contribute to the problem.

Is the motor driving things by belt? If it is a 50-60hz thing, you could down size the motor pulley to slow the machine and ease the work on the motor.

Is the motor installed where there is free air flow, not attached to something really hot, and not covered with dirt & fuzz, which will insulate it?

I have in the past mounted an axial computer style fan at a motor to help move air.

Good luck !

Pete

Don't be so sure... *LINK*

Tim Greif - West of Chicago

You really can't reliably use touch to gauge a motor's temperature as being acceptable or not. The article below is a pretty good discussion of this. In my previous occupation as an engineer before I retired, I frequently used electric valve actuators for modulating control valves. These were specified with Class H insulation which was suitable for winding temperatures up to 180 degrees C due to the frequent motor starts. I can assure you that you could not put your hand on these actuator motors for more than a fraction of a second without getting burned. And they continued to operate that way year after year with no problems. I realize this is an extreme case, but it's food for thought in considering whether or not that motor of yours is really overheating or just operating as hot as it was intended.


Leeson Motor Temperature article

testing by comparison

John K Jordan

Never trust the wiring but measure the voltage at the motor, best at the connection point inside the motor. This just to eliminate the possibility that something is not wrong with the voltage at that point.

Second, put a clamp-on amp meter on one of the supply wires at the motor and check the amperage while the motor is running under load. To get the clamp around just one wire may require some creativity. Then compare to a similar motor that does not overheat, also under similar load.

You have a big advantage of more than one identical motor, at least one of which works correctly. This is the easiest case possible for debugging by elimination of possible problems one at a time by testing and comparison.

JKJ

Re: Yep

Larry Clinton At Frankfort, (Central) Indiana

I worked at a motor repair shop for over a year when I was a young lad. I was given a motor to repair due to bad bearings. I cleaned up the motor, replaced the bearings, load tested it on our dynamometer, set it on my bench and let it run. I started another job, then reached over to move the motor, blistered my finger! THEN I looked at the motor rating, the operating temperature was extremely high, As I recall over 200F. I checked temperature rating on any motor with glass insulation after that.

Interesting!

Tony - Memphis

I have some old fans (induction? - no brushes) that run extremely hot! Hmm, I ought to check the case temp with my Ir thingie. Anyway, these are old desktop oscillator fans that have been running for many many years. Love those things. One was my great uncle's - bought it in the 20's I think and he used it in his workshop before I got it. All I did was clean it and I keep it oiled.

One might question the efficiency of creating so much heat! I've noticed that some of the stepper motors I use in various stuff run very hot too.