Motor Quality Issues, Fact or Fiction 2

[PNA]

Good morning,

1) Is it normal for a 1/2 HP TENV single phase motor to run 320 degrees fahrenheit under no load and is it a fair comparison to test a motor under no load?

2) If a motor runs this hot and it is considered normal, wouldn't using high temperature insulated wire be prudent?

3) What are the best methods to test the quality of a motor before spending valuable time being assembled into final production equipment.

4) Who are the 5 best custom motor manufacturer's around the world?

5) What tolerance is acceptable between the rotor and stator? What can be deemed excessive pulsation when running a motor of this type?


Any assistance would be appreciated

Regards

Paul

 

[jclough]

I can answer your questions but the meaning of the term TENV escapes me.

 

[dbaird]

TENV = Totally Enclosed Non-Ventilated

TEMPERATURE
Ambient Temperature
Ambient temperature is the maximum safe room temperature surrounding the motor if it is going to be operated continuously at full load. In most cases, the standardized ambient temperature rating is 40°C (104° F). This is a very warm room. Certain types of applications such as on board ships and boiler rooms, may require motors with a higher ambient temperature capability such as 50° C or 60° C.

Temperature Rise
Temperature rise is the amount of temperature change that can be expected within the winding of the motor from non-operating (cool condition) to its temperature at full load continuous operating condition. Temperature rise is normally expressed in degrees centigrade.
The common insulation classes used in electric motors at the present time are Class B, Class F and Class H. The present frame size assignments are based on Class B insulation. It is the predominant class of insulation used in motor manufacturing today. Based on a 40 degrees C ambient temperature, the Class B insulation is suitable for 80 degrees C rise by resistance. Class F insulation is suitable for 105 degrees C rise by resistance. Class H insulation is suitable for 125 degrees C rise by resistance. Use of Class F insulation or Class H insulation can increase the service factor or the ability to withstand high ambient temperature conditions.




David Baird
mrbaird@hotmail.com

Sr Controls Engineer

EET degree.

Journeyman Electrician.

 

[jOmega]

DBaird:

In considering your definition of Ambient Temperature, the question arose: [ul]What would the room temperature be if the object is installed in the great outdoors ??[/ul]
Perhaps the use of Webster's definition of 'ambient' would better serve to define Ambient Temperature[ul][li]Ambient: an encompassing atmosphere [/ul][/li]Ergo: Ambient Temperature: the tempature of the atmosphere encompassing or surrounding the object of consideration...

 

[jclough]

Hi Paul,

320 deg F does sound a bit toasty even for a class H motor. That doesn't leave much room for temp rise due to the load. We've made motors like that before but they only needed to operate for 40 sec. I suggest you check and compare your motor specs. What kind of motor is it?

As far as pre assembly testing is comcerned...I would recommend a hipot or megger just as a safety check. At our facility all of our motors are performance tested before shipment. Rarely, defects arise during shipment or storage. These defects however are of the type where either the damage is clearly visible or the motor doesn't run at all. you will have to decide if it's worth the money to test before hand. If you do decide to test, I suspect a simple test to see if the motor runs and sounds good would suffice.
Buy a motor with the quality built in...that way you won't have to check to see if its there.

Regarding the best custom motor supplier....we'll I'm biased as I work for one but EAD motors builds a nice product.

As far as the stator and rotor tolerance is concerned, the airgap will vary with the motor size, type and/or performance requirements. Steppers have air gaps in the .003" range, induction motors have much more air gap. The pulsing you refer to maybe caused by a great number of things, some being indications of defects and some not. It would help if I knew more about the motor

 

[SteveKW]

Typically, a TENV motor shouldn't be run unless it is in an air stream. Those motors will get very hot testing them since you dont have the fan blade or squirrel cage blower (load) drawing air across it to keep it cool!

 

[jbartos]

Suggestion to PNA (Industrial) Dec 16, 2003 marked ///\\1) Is it normal for a 1/2 HP TENV single phase motor to run 320 degrees fahrenheit under no load and is it a fair comparison to test a motor under no load?
///TdegC=(5/9)x(320-32)=160degC. The TENV motor has to have NEMA Class H insulation system (180degC including a 40degC ambient and 140degC temperature rise).\\2) If a motor runs this hot and it is considered normal, wouldn't using high temperature insulated wire be prudent?
///The motor is operating in the high temperature range; however, it may be within its design baseline.\\3) What are the best methods to test the quality of a motor before spending valuable time being assembled into final production equipment.
///Simulate the would be conditions and run the motor.\\4) Who are the 5 best custom motor manufacturer's around the world?
///Visit

http://www.thomasregister.com

and type Motors: Electric under Product of Service, which will return 505 companies to approach to regarding 5 best custom motor manufacturers in the world.\\5) What tolerance is acceptable between the rotor and stator?
///It depends on the motor precision and application.\\ What can be deemed excessive pulsation when running a motor of this type?
///The power supply larger harmonic content can cause the motor vibrations.\\\

 

[PNA]

Thankyou for the responses.

It is a ClassB motor
Class F4 Insulation
S.F. 1.00
Nema Eff. 72%

Lets put the wiring question this way,
the wires are on the melted side (turning from a solid to a slow liquid)

When taken apart, there are 'black score or burnt spots' on the rotor.

This motor is supposedly balanced above Mil-Spec.

Are there any comprehensive books on electric motors and motor manufacturing?

Regards

Paul
Mechanical/Mechatronics Engineering Technologist

 

[aolalde]

Paul:
Electric Motors are manufactured in USA under NEMA MG1 standards. More than 20 manufactures provide high quality motors. The main problem I have seen for many years is a poor motor selection or application.
My first concern with your problem is Why a TENV motor? Did you selected that type or just was the motor available? TENV motors are regularly for very short time operation rating. TEAO (totally enclosed air over) are used when the load provides enough air ventilation but TEFC (totally enclosed fan cooled) are the best option for general applications.
The performance you described is that of a motor with terminal leads melting. Did you verify the name plate data for Voltage and wiring connection?
I suggest you should consult an expert in motor application to select the motor that matches your load and power supply requirements.

 

[PNA]

Standards and consistency would be 2 of many reasons I am asking the above questions.

The reason for a TENV motor? I don't know.
I have confirmation it is rated for continuous duty.
It is placed in a dusty environment and must not create a spark source. This particular motor was actually recommended and spec'd out for the purpose we are using it for. (Apparently by a motor expert).


These motors were spec'd long before I started working at where I am. I am just trying to get some hard numbers and facts.

The unfortunate thing about TEFC motors that I have experienced are the crappy plastic cooling fans that end up falling off or spinning on the shaft after being used for start/stop applications plus noise is a factor.

I am getting information from our suppliers engineerings who design and manufacture motors for a living and get baffle-gab half the time.

I have perused the internet and have only 2 of many motor manufacturers (custom or not) that will even quote a motor as precise as we require it.

I was told that what I am looking for is "IDEALISTIC" in terms of motor manufacturing and can't be done"

I don't believe that for a second.

If we have CNC machines that machine down to the millionths, then a motor should not be a problem.
I don't see anything complex about TENV's.
Take them apart and there isn't much in there.
I would assume that rotating part can be made to run in the tenths of a thousanths within the stationary outer windings?

Maybe I am dreaming, but I want to learn and understand the particulars of manufacturing a TENV and what can be achieved.

Runout of the shaft of tenths?

Thanks for all the help

Paul

 

[jbartos]

Suggestion: Check with major motor manufacturers offering custom features, e.g.

http://www.reliance.com/pdf/brochures/raps_498.pdf

http://www.mckechnieaerospace.com/welcotech/asp/wt_aboutus.asp

http://www.industrialsupplyco.com/Catalog/CONTROLACVARIABLE SPEEDDRIVES.pdf

for: TENV Class H motors
etc. for more info