Hot motor
 

My Taig is powered by a 110V 1Ph 1750 rpm 1/4 HP induction motor or garage
sale provenance. My concern is that with use it gets too hot to touch.

I noticed that it was quite warm when I hooked it up first around February.
I have used the Taig for brief periods only until now when the heating
became quite noticeable.

I run a test today:

1) I run my drill press (3/4HP) for 5 minutes. In an ambient temp of the
garage of 27.5C the motor heated up from that to 37.0C.
2) I run the Taig motor without the belt for 5 min. The ambient temp by
then was 28.5C and the motor reached 39.1C
3) I repeated the run with the belt and a chuck on the spindle - no other
resistance. Unfortunately by then the ambient temp was 32.2C and the motor
started at 34.2C. After 5 minutes the temp was 46.1C.
4) I repeated the run with the drill press (ambient 30.9C, went from 31.1 to
40.4C).

The temperatures were measured by an IR thermometer.
There was a gradient of temperature in both motors: The front of the Taig
motor was considerably warmer than the back, the reverse was true of the
drill press motor.
The increased temperature was confined to the housing - the shaft and the
pulley on it were quite cool (almost 10C cooler).
There were no unusual noises or smells, no evidence of sparking.
The motor runs smoothly and quietly.
The pulley/belt alignment is good as judged by conventional methods.

Questions:

1) Is such degree of heating abnormal? I have never encountered a motor that
heats up this much so I assume the answer is yes.
2) What is the likely cause? My first thoughts was "bearings" but why would
the housing be hotter than the shaft? Superficially there is nothing to
suggest that the bearings are at fault.

Thanks,

--
Michael Koblic
Campbell River, BC

Hot motor
 

I vote for it does not matter. Nobody runs a drill press for five
minutes anyway.

Your motor should have a temperature rise in celsius stamped on the
nameplate, or alternatively insulation class. If you post this info,
or the whole nameplate, someone here could tell you whether the
observed temperature rise is justified. Many modern motors are
designed to run relatively hot.

You can get a perfectly quantified answer to your question if you
post nameplate data.

i

Hot motor
 

Michael Koblic wrote:
My Taig is powered by a 110V 1Ph 1750 rpm 1/4 HP induction motor or garage
sale provenance. My concern is that with use it gets too hot to touch.

I noticed that it was quite warm when I hooked it up first around February.
I have used the Taig for brief periods only until now when the heating
became quite noticeable.

I run a test today:

1) I run my drill press (3/4HP) for 5 minutes. In an ambient temp of the
garage of 27.5C the motor heated up from that to 37.0C.
2) I run the Taig motor without the belt for 5 min. The ambient temp by
then was 28.5C and the motor reached 39.1C
3) I repeated the run with the belt and a chuck on the spindle - no other
resistance. Unfortunately by then the ambient temp was 32.2C and the motor
started at 34.2C. After 5 minutes the temp was 46.1C.
4) I repeated the run with the drill press (ambient 30.9C, went from 31.1 to
40.4C).

I suspect that the motor is fine. Design of a motor affects the
temperature of the case. Some get noticeably hotter than others. 40 deg.
C isn't that hot. Plenty of motors are rated for operating continuously
in a 40 deg. C atmosphere. The windings will be somewhat hotter than the
case, but they'd probably need to reach more than 100 deg. C to do them
harm. If you want an accurate indication of the winding temperature
rise, Jim Cox's book "Electric Motors in the Home Workshop" explains how
to measure it using the change in resistance.

Best wishes,

Chris

Hot motor
 

"Michael Koblic" fired this volley in
:

1) Is such degree of heating abnormal? I have never encountered a
motor that heats up this much so I assume the answer is yes.

It doesn't sound terribly out of line. Decently-made motors typically
are rated for an _internal_ temperature rise of up to 40C.

2) What is the likely cause? My first thoughts was "bearings" but
why
would the housing be hotter than the shaft? Superficially there is
nothing to suggest that the bearings are at fault.

If it's one of those light-housing open-frame motors, there can be
some eddy losses in the frame as well as the stator. Plus, the stator
is usually in intimate contact with the frame, and conducts copper
loss heat as well as stator excitation losses into the frame.

LLoyd

Hot motor
 

DoN. Nichols wrote:

The motor for the Taig (if it is like mine) is a self-starting
induction motor -- done by "shading" on the poles -- formed by a heavy
copper wire welded to form a single shorted turn over only part of the
pole. This loses energy as heat -- the smaller the wire, the hotter it
will get with the induced current -- but it is necessary to get the
motor to start. This is probably a significant part of the heat source
in your Taig's motor.

If it's a shaded pole motor, getting very hot is normal. They're
designed to run that way. Shaded pole motors are inefficient compared to
other types of motor (for the reason Don gives above). Some get too hot
to touch even when running unloaded.

Best wishes,

Chris

Hot motor
 

Michael Koblic wrote:
My Taig is powered by a 110V 1Ph 1750 rpm 1/4 HP induction motor or
garage sale provenance. My concern is that with use it gets too hot
to touch.

etc.etc.

Thank you all for helpful responses.

The insulation class is B so the temperatures seem well within acceptable
limits.
I could find no evidence of a capacitor so shaded pole is the most likely
explanation.

To fill in the details some of you commented on:

1) The IR thermometer read within 1.5C of a thermocouple on all surfaces
except the shiny ones where the diff was 2C.
2) To confirm that the pulley/shaft were indeed cooler than the housing I
used the scientific method of touching both.

All in all a satisfactory result.

--
Michael Koblic
Campbell River, BC

Hot motor
 

On Aug 2, 5:59*pm, "Michael Koblic" wrote:

Questions:

1) Is such degree of heating abnormal?

Sadly no.

2) What is the likely cause? My first thoughts was "bearings" but why would
the housing be hotter than the shaft? Superficially there is nothing to
suggest that the bearings are at fault.

It's the motor design. Cheap to make, not so good to run. People have
had much better results with a 24 VDC electric scooter motor, about
150 W. You can machine steel for 30 minutes and the motor barely warms
up, plus you get excellent speed control. They are being surplused
right now.

Hot motor
 

On Mon, 3 Aug 2009 19:07:47 -0700 (PDT), N Morrison
wrote:

On Aug 2, 5:59*pm, "Michael Koblic" wrote:

Questions:

1) Is such degree of heating abnormal?

Sadly no.

2) What is the likely cause? My first thoughts was "bearings" but why would
the housing be hotter than the shaft? Superficially there is nothing to
suggest that the bearings are at fault.

It's the motor design. Cheap to make, not so good to run. People have
had much better results with a 24 VDC electric scooter motor, about
150 W. You can machine steel for 30 minutes and the motor barely warms
up, plus you get excellent speed control. They are being surplused
right now.
My little DP came with a 1/6 HP motor that would get too hot to touch
almost before you turned it on. Now it has a 1/3 HP I bought three for
a dollar and I can work all day and still grab it.
Gerry :-)}
London, Canada

Hot motor
 

On Aug 3, 6:51*pm, "Michael Koblic" wrote:

I could find no evidence of a capacitor so shaded pole is the most likely
explanation.

1/4 Hp is VERY large for shaded pole - I'd expect split phase with a
centrifugal starting switch. That's pretty well standard for an
unloaded start application.

Hot motor
 

On Tue, 4 Aug 2009 10:49:11 -0700 (PDT), N Morrison
wrote:

On Aug 3, 6:51*pm, "Michael Koblic" wrote:

I could find no evidence of a capacitor so shaded pole is the most likely
explanation.

1/4 Hp is VERY large for shaded pole - I'd expect split phase with a
centrifugal starting switch. That's pretty well standard for an
unloaded start application.

Motors up to 3/4 hp were used back in the '30s and '40s. They didn't need a
starting condenser, slip rings or centrifugal switch. They did run hot, but
were often not continuously rated.

I had one on a 1942 drill press.

Mark Rand
RTFM

Hot motor
 

Michael Koblic wrote:
Michael Koblic wrote:

My Taig is powered by a 110V 1Ph 1750 rpm 1/4 HP induction motor or
garage sale provenance. My concern is that with use it gets too hot
to touch.


etc.etc.

Thank you all for helpful responses.

The insulation class is B so the temperatures seem well within acceptable
limits.
I could find no evidence of a capacitor so shaded pole is the most likely
explanation.

Thinking about this a little more, I doubt it's a shaded pole motor.
I've never seen a shaded pole motor as big as 1/4 hp (if anyone has, do
let me know). Usually the biggest is about 1/16 hp. Above that the power
losses get significant.

It's probably a split-phase motor. These have two windings: the main
winding, which has a high inductance and a low resistance, and the start
winding, which has a low inductance and a high resistance. As a result,
the two magnetic fields produced are out of phase, which is the
condition required for starting. There will be a switch somewhere to
control the start winding. Either a centrifugal switch, a relay or a
special momentary switch (the second two are fairly rare). Split-phase
motors do not require a capacitor, but their starting performance is
poorer than that of capacitor-start motors.

Best wishes,

Chris

Hot motor
 

Mark Rand wrote:
On Tue, 4 Aug 2009 10:49:11 -0700 (PDT), N Morrison
wrote:


On Aug 3, 6:51 pm, "Michael Koblic" wrote:


I could find no evidence of a capacitor so shaded pole is the most likely
explanation.

1/4 Hp is VERY large for shaded pole - I'd expect split phase with a
centrifugal starting switch. That's pretty well standard for an
unloaded start application.


Motors up to 3/4 hp were used back in the '30s and '40s. They didn't need a
starting condenser, slip rings or centrifugal switch. They did run hot, but
were often not continuously rated.

I had one on a 1942 drill press.

Was it definitely a shaded pole motor? If so, I'd be interested to see
one of these. An unusually large shaded pole motor is a type I haven't
seen, and I'm fond of early motors.

There was another kind which didn't need a capacitor, slip rings or a
centrifugal switch. It has a special start-run switch with momentary and
latching contacts for the two windings. Bob Minchin kindly gave me one.

Best wishes,

Chris

Hot motor
 

On Sun, 2 Aug 2009 17:59:10 -0700, "Michael Koblic"
wrote:

My Taig is powered by a 110V 1Ph 1750 rpm 1/4 HP induction motor or garage
sale provenance. My concern is that with use it gets too hot to touch.

I noticed that it was quite warm when I hooked it up first around February.
I have used the Taig for brief periods only until now when the heating
became quite noticeable.


I powered my taig, before I gave it away, with the enclosed motor from
a floor mounted fan. this ran very hot over time.
sooooo I mounted a computer fan to blow air over it.
it still got warm but not so much that it caused any concern.

you do have a cooling air supply blowing over it???
all the bigger motors have a centrifugal blower built in so dont need
the assistance. a mains voltage computer fan and a lash up shroud
should fix it.
Stealth pilot