Suggestions for this Auger Motor Failure Analysis - Tests?

[Don2222]

Hello

I finally have a stove I am rebuilding where the Auger Motor failed after the stove fires up. The vacuum switch and vacuum hose was replaced and the High Limit switch tested in good working order with a brand new control board.

Since all other components in the auger power circuit were good, I replaced the auger motor and the stove is running fine now.

I really wish there was a meter I could put on the motor that showed a needle in the red or bad range?

What is the next best test? Is there a good test that does not require thousands in test equipment?

Is there a good way to measure the strength of the magnetic field? How worn the gears are in the gear box? etc?

This 2 RPM Merkle-Korff Inc. gearbox auger motor was pulled from a Pelpro HHPP2BD approx 6 years old. MFD is not visible in pic

See pics below
Click to Enlarge

 

[Harvey Schneider]

Hello

I finally have a stove I am rebuilding where the Auger Motor failed after the stove fires up. The vacuum switch and vacuum hose was replaced and the High Limit switch tested in good working order with a brand new control board.

Since all other components in the auger power circuit were good, I replaced the auger motor and the stove is running fine now.

I really wish there was a meter I could put on the motor that showed a needle in the red or bad range?

What is the next best test? Is there a good test that does not require thousands in test equipment?

Is there a good way to measure the strength of the magnetic field? How worn the gears are in the gear box? etc?

This 2 RPM Merkle-Korff Inc. gearbox auger motor was pulled from a Pelpro HHPP2BD approx 6 years old. MFD is not visible in pic

See pics below
Click to Enlarge

The only thing that comes to mind is measurement of motor current. An unloaded motor (stripped gears, loose coupling) would draw less than normal current. A stalled motor would draw higher than normal current. A burned out coil would draw no current.
You would have to have an idea of what is normal current for the application. It is not the motor label current. That current draw only occurs when the motor is at a specified load.
Measurement is easy with a clamp on AC meter.

 

[Mt Bob]

Well,I won't take the time to put anything together,but give you some ideas.A jig to mount it in,a device to add/subtract load on the shaft(easily done).Being an induction motor that small I do not think amp measurement will mean anything,however your ears will.Nice thought,but it's a $100 motor.Just some thoughts.

 

[MountainSean]

Good old resistance test. The non exact or scientific measurement. Try to stop the thing with a pair of pliers. I suppose you could work up a combination with a vise and a torque wrench and measure the torque the motor produces vs what it should produce before it stalls.

 

[Don2222]

Hello

Measuring torque may be a good way, but most of the tools I have seen for that are for a mechanics rachet.
Since the Gleason-Avery has up to 250 in/lbs of torque, this would be a good number for comparison.

Not sure if this tool would work? Looks like it would tighten down on the auger motor shaft? Then what?
http://www.globalindustrial.com/p/t...Force/economical-torque-gauge-50ozin-capacity

I was thinking of measuring the strenght of the electromagnetic field?
This would tell if the coil windings were breaking down or shorting.
This would be related to torque, however any worn gears would not show up.
Not too expensive.
(broken link removed)

 

[Mt Bob]

Hello

Measuring torque may be a good way, but most of the tools I have seen for that are for a mechanics rachet.
Since the Gleason-Avery has up to 250 in/lbs of torque, this would be a good number for comparison.

Not sure if this tool would work? Looks like it would tighten down on the auger motor shaft? Then what?
http://www.globalindustrial.com/p/t...Force/economical-torque-gauge-50ozin-capacity

I was thinking of measuring the strenght of the electromagnetic field?
This would tell if the coil windings were breaking down or shorting.
This would be related to torque, however any worn gears would not show up.
Not too expensive.
(broken link removed)

No,I was thinking simple jig,shaft would have to be mounted to larger,or wheel,leather wiper with hand adjustment to tension.If you got creative,could put continious inch lb meter on other end.Right about measuring mag. field.Current readings would be very small,less than .6 amp,and highest reading would be right before it starts.Mag reading could tell you a difference,such as insulation problem.Quick simple,put load on it and listen.Also watch stalling these motors,most have a plastic or sintered metal breakaway gear inside.Don't know why,can't get repair parts.Now back to fixing plow pump,catch you later.

 

[Harvey Schneider]

Anything that stalls the motor runs the risk of wiping out the gear train.
I don't see why current measurement wouldn't work. These motors pull about 0.4A at nominal load. Maybe too low for a typical clamp on, but a small resistor in series for measuring current would work. Measure the Voltage drop across the resistor.
A Kill A Watt meter should be able to resolve 10ths of an Amp.

 

[Don2222]

Anything that stalls the motor runs the risk of wiping out the gear train.
I don't see why current measurement wouldn't work. These motors pull about 0.4A at nominal load. Maybe too low for a typical clamp on, but a small resistor in series for measuring current would work. Measure the Voltage drop across the resistor.
A Kill A Watt meter should be able to resolve 10ths of an Amp.

Good suggestion about the Kill-a-Watt meter. I do have one I can try with a test cord to the failed motor and to a good motor for comparison! ! !

 

[SwineFlue]

A Kill A Watt meter should be able to resolve 10ths of an Amp.

Would the KillAWatt's Power Factor (VA vs. Watts) say anything about the state of a motor?

 

[Harvey Schneider]

Would the KillAWatt's Power Factor (VA vs. Watts) say anything about the state of a motor?

Yes it would, but I have to think on how that might be useful.
A lightly loaded motor will have a lower power factor than a heavily loaded motor. What does that say about the function of the motor? You could see if a motor is stalled vs not coupled to the auger. Not terribly useful, my eyes can tell me that.

 

[Don2222]

Yes it would, but I have to think on how that might be useful.
A lightly loaded motor will have a lower power factor than a heavily loaded motor. What does that say about the function of the motor? You could see if a motor is stalled vs not coupled to the auger. Not terribly useful, my eyes can tell me that.

I found the Kill-A-Watt meter and checked the instructions to see what measurements it makes. The amp scale is very good

Volts are displayed in Volts (true RMS), Current is displayed in Amps (true RMS), Watts are displayed in active power Watts, VA is displayed in apparent power VA (VA=Vrms*Arms), Frequency is displayed in Hertz (Hz), Power Factor (P.F.) is displayed as (Watts/Vrms*Arms).

I just plugged a 14 watt CFL rated at 0.23 amps
As a baseline for reference:
It measured 0.20 amps at 119.0 volts with P.F of 6.1 at 60 HZ @ 22.1 VA for 13.5 watts on the watt meter!

Well, I just measured the failed Auger Motor
It measured 0.01 Amps at 119.1 volts with P.F. of 0.41 at 60 Hz @ 1.2 VA for 0.4 watts on the meter

Problem is that a new motor had just about the same values. No smoking gun here.
Seems like the values are so low that there is not much different.

 

[Mt Bob]

Yep.

 

[Don2222]

Hello

Maybe going with a consulting service like G2 Consulting for Motor Torgue Testing and Dynomometer for small motors?
http://www.consult-g2.com/

Or

Maybe consuting on failure analysis
http://www.tribology.co.uk/services/investigate/index.htm

In this case the failure seems to be due to Thermal Instability
This failure mode occurs when a large temperature difference builds up between the shaft inside a bearing and the housing surrounding the bearing. The differential thermal expansion causes the bearing to lose internal clearance and become pre-loaded. This results in increased heat generation which will increase the differential temperature. This is positive feedback which rapidly leads to thermal runaway and melt-down.

Click on pic below to enlarge:

 

[Harvey Schneider]

It measured 0.20 amps at 119.0 volts with P.F of 6.1 at 60 HZ @ 22.1 VA for 13.5 watts on the watt meter!

You must have misread. Power factor cannot exceed 1.

edit
The definition of power factor
PF = Watts / (Volts x Amps) = Volts x Amps x Cos (phase angle)
Since the cosine of the phase angle cannot exceed 1 PF cannot exceed 1.

The phase angle between Volts and Amps is caused by the inductance of the motor. When the motor is doing work the phase angle get smaller (looks less inductive and more resistive) and the cosine of that angle increases. (cos(0) = 1).

 

[SwineFlue]

You must have misread. Power factor cannot exceed 1.

edit
The definition of power factor
PF = Watts / (Volts x Amps) = Volts x Amps x Cos (phase angle)
Since the cosine of the phase angle cannot exceed 1 PF cannot exceed 1.

The phase angle between Volts and Amps is caused by the inductance of the motor. When the motor is doing work the phase angle get smaller (looks less inductive and more resistive) and the cosine of that angle increases. (cos(0) = 1).

The decimal point was misplaced: 13.5 W / 22.1 VA = 0.61 (instead of 6.1)

 

[pete324rocket]

did you see my post.Maybe your bushings are worn like mine. I expect there will be a lot of these hitting the landfill soon-slip in some real bearings: https://www.hearth.com/talk/threads...bearing-switcheroo-trick.108028/#post-1652574