Hot motor

[stevhop]

The motor on my T-7 gets too hot to touch after about 45 min. Is this normal?

Thank you for any help you can give me.

[grepper]

Welcome to the forum stevhop.

How old is the T7?  How many hours of use?

How long has this been happening?

When it is cool, does it spin freely?

If you turn it off when it is hot, does it spin freely?

Any strange noises when it is spinning?

You should email Tormek support directly.  Too much overheating will damage the winding insulation and can cause permanent damage or catastrophic failure.

[SharpenADullWitt]

http://forum.tormek.com/index.php?topic=1435.msg4564#msg4564

In the last post Jeff, says the motors do run hot.   Mine ran for about an hour today and the housing did feel warm to me.

[grepper]

Really?  Too hot to touch is normal?

Every get a funny electrical smell?

[Mike Fairleigh]

"Too hot to touch" is normal for many electric motors.  What's important is that they be built to handle the heat.  That's the main difference between a $50 motor and a $300 motor.  I have induction motors by Baldor and Leeson that run that hot, and are rated to do so all day long, 7 days a week.

My T7 has been the same way since new.

[grepper]

So I checked the spec plate on the T7 motor and it carries a 155 (F) insulation thermal rating, which incidentally, is the same rating as the Baldor motor on my belt grinder.  A class F thermal rating is 155 degrees C or 311 degrees F.

http://www.engineeringtoolbox.com/nema-insulation-classes-d_734.html

This specifies the insulation to use, "Inorganic materials such as mica, glass fibers, asbestos temperature binders, or others with usable lifetime at this temperature".

So I guess the thing can get pretty toasty and still be just fine.  I never realized it was running that hot, and when I think about it, I have never turned the T7 over felt the motor after using it.  Interestingly, the combustion point of paper is only about 100 degrees hotter. 

So I guess as long as you don't smell that wonderful aroma of melting insulation and the thing rotates freely, it can be cooking away down there and be just fine.

I found that interesting.  That's for the motivation to check it out!

[Mike Fairleigh]

Yep, motors are one thing where you really have to trust the manufacturer and their ratings.  It goes against our grain to see a motor run that hot and not care.  This is why most motors don't have as much data on their plate as Baldor-class motors do - it's not that the manufacturer doesn't know the data, it's that they don't want you to know.

It extends to horsepower too.  In order to know the true HP of a motor, you have to solve:

(Volts x Amps x Power Factor x Efficiency Rating) / 756.  Few manufacturers below the Baldor class will tell you the PF or ER, because if they give you those, they can't claim that their $25 motor produces 5hp when connected to 120VAC mains.  (Actually most motors fail the HP test without even considering PF or ER - just ask Sears with their 6HP shop vacs  .)

[stevhop]

Thank you for the replies.
Response to grepper: T-7 is relatively new, approx. 20 hours of use so far.
                               Has been running too hot to touch since new.
                               Spins freely when shut down, and when cool, no noises.
If I understand, the general consensus of the rest of the replies, is that this is normal....yes?

Thank you

[Ken S]

Stig, I would guess that Tormek AB has done testing on acceptable and unacceptable heating of the motors. Could you share the results of those tests with the forum?

Ken

[Stickan]

No need for worries, it is normal that it gets around 50 degree Celsius, about 122 Fahrenheit.
Even some degrees up is no problem.

Stig

[grepper]

An interesting article about motor temp on the Baldor site:
http://www.baldor.com/news/article.asp?id=978

[Rhino]

I laugh whenever I see a motor rated at 5 hp on 120v.  1 horsepower is something like 750 watts.  At best, a motor using house wiring is a little better than 2 hp and this will assume 100% efficiency.  Any name plate saying otherwise is being deceptive and probably measuring instantaneous power if you stop the motor cold turkey

[Ken S]

These posts have solved an old problem for me.  My coffee invariably gets cold in the shop.  Now I know I can just set the mug on my Tormek!  Actually, I haven't noticed my Tormek running that hot.  I run mine more intermittently.

Ken