PM-1236 motor issue

[tino_ale]

Hi guys,

Thanks for all the feedback.

Might try running the motor (with the belt removed) for about 1/2 hour continuously... then take its temp again. A motor running with NO load, should not heat up at all... that would be a significant clue.

I'm going to try that good idea.

Not sure if you have any motor shops in your area... we have them around me and they could tell if I took the motor to them... or you Emailed them the video.

Unfortunately no, there are no small shops around here anymore.

You probably already thought of this, but aren't yall on 220v 50 Hz? Is it a 60 Hz motor? Don't know if it would make a difference or not, just a thought. The bead looks cool with those lines in it, though!

During the ordering process Matt told me 50/60Hz would be fine, and I don't think it would mess up with the motor like that. I'm not an expert though.
Yeah the finish really came out funky. Funny thing is, with a smooth running machine, I would be absolutely clueless if someone asked me to make another one like that.

Doesn't sound right. I'd say you have a stuck centrifugal switch, but I think I hear it operating when you turn the motor off and it spins down. Have you made sure it's wired correctly?

I also think I hear it operate at the end of the free spinning.
About the wiring : how could it possibily be badly wired ? There is only neutral, phase and ground right ? I don't know what kind of incorrect wiring would produce that issue

The hum sounds like an electrical issue... as thought the motor is fighting with itself.

I completely agree with you. At the second I shut the power off, 90% of the sound and vibrations immediately stop.


I have contacted Matt yesterday and waiting on his reply.

Will keep you posted!
thanks again

 

[mksj]

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <wunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <woNotPromoteQF/> <w:LidThemeOther>EN-US</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> <w:SplitPgBreakAndParaMark/> <wontVertAlignCellWithSp/> <wontBreakConstrainedForcedTables/> <wontVertAlignInTxbx/> <w:Word11KerningPairs/> <w:CachedColBalance/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument> </xml><![endif]--> [FONT=&quot]After some additional research, there were three points that came to light and could account for your motor issues.[/FONT]
[FONT=&quot]A single phase 60 Hz motor can be run on 50Hz if the voltage is proportionally reduced (V/Hz ratio), so in this case you would need to run the motor on something like 190V. The motor will run 20% slower and the Hp will be derated by 20% or more. Running a 60 Hz motor at 50Hz on 230V means that during part of every power line cycle the magnetic structure of the motor will probably be overloaded. This will cause excessive current to flow heating the motor quickly, which is what you are reporting. I have also seen this in various types of transformers in equipment, they quickly burn up.[/FONT]
[FONT=&quot]When a 60Hz single phase motor is brought down in frequency the centrifugal start switch may not ever reach opening speed. Given that the switch opening speed setpoint is usually set at around 80% of running speed, it may not be disengaging. If it doesn't reach switch speed, smoke is definitely on the way!
[/FONT]
[FONT=&quot]Single phase motor start and run capacitor are designed for a specific frequency and voltage, when lowering the frequency their affect is reduced, and can derate the performance of the motor. Usually incorrect sized or damaged start/run capacitors will result in motor overheating.[/FONT]

[FONT=&quot]Check the name plate ratings on your motor. It specifies 220V at 60Hz, then you probably need to replace the motor if you do not reduce the mains voltage. In most cases, this simplest and most cost effective solution is to replace the single phase motor with a 220-240V 50Hz model. The alternative is to go to a 3 phase motor with a VFD, which is what I did on my PM lathe.[/FONT]

 

[tino_ale]

Ok so I checked both the Lathe ID plate and the motor plate. Both say 220V and 60Hz. Not 50Hz.

Here is the motor plate :

Those are not really reassuring news... don't know what to think!
I came home too late tonight to run the motor free of any load and recheck the temp.
I am sure about the very high temp when I broke the lathe gears in, and back then oil level was normal, oil viscosity ISO 68, nothing in the chuck and finally I have checked my spindle preload and all seem fine.

The centrifugal thing, honestly I don't even know what this is, but I think I hear it click near the end of free spinning after I shut the motor off in my video. As if it was re-engaging. It is there in the video. Not sure if it is enough to rule out that possible issue.

Let's see what Matt thinks about that motor.

What I know for a fact is that I asked about both the voltage and frequency to Matt prior to ordering and he was clear that would be no problem at all to run under 220V and 50Hz.

Now, I have not run the lathe for dozen of hours yet, but I have broken-in the gears and used it a little (to make the Ti bead and a few other parts). If I do fix it with a new cap or whatever it would be, I hope it has not suffered some permanent damage.

It also occurred to me that the rest of the lathe is 60Hz spec, I hope other electrical components will not suffer from an improper frequency supply.

 

[John Hasler]

While that motor might not deliver a full 1.5kW on 50Hz it should idle just fine without making a lot of noise or getting hot. Can you measure how much current it's drawing?

 

[tino_ale]

I have one of those watt-meter that I plugged between the lathe and wall outlet.

Lathe ready, all off :
0.35A / Power factor 22

Lathe light turned on :
0.45A / Power factor 75

Motor on (no belt on) :
19.5A / Power factor 30

No do not quote those numbers, I don't understand why the power factor changes like that.
I don't know if that is normal or if the meter is fooling around.

Tried it on a light I have (40W bulb), said 0.2A / power factor 100
Then on my dyson fan :
off : 0.01A / PF 30
on : 0.2 / PF 70

Don't know if that helps. Again I have my doubts on that meter and I don't know if it can be trusted. Unfortunately I have no other mean to measure the actual current draw of the motor.

 

[John Hasler]

The numbers for the fan and the light are as I would expect. Something in your lathe is drawing a little bit of current when it is "off". The numbers for the motor indicate that it is defective. I think that your centrifugal switch is stuck or somehow bypassed so that it's in the circuit all the time: that's about how much current it would draw. Perhaps they swapped the start and run capacitors at the factory?

I'd open that motor up and check the wiring.

 

[tmarks11]

Motor on (no belt on) :19.5A / Power factor 30

:yikes:

What ever you do, don't run the thing any more until you solve the problem. That is almost 3x the label plate current (7.3A)... it is drawing more current than a 5HP fully loaded motor.

200F? While the NEMA Class B Insulation is rated at 266F, I bet the internal temp of the motor is near or past the limit. Any additional operation is going to kill the motor... and probably start a fire. Fire extinguisher handy?

Do you have a phototach? Bet you the motor is NOT spinning at 1680 rpm.

 

[GA Gyro]

I have one of those watt-meter that I plugged between the lathe and wall outlet.

Lathe ready, all off :
0.35A / Power factor 22

Lathe light turned on :
0.45A / Power factor 75

Motor on (no belt on) :
19.5A / Power factor 30

No do not quote those numbers, I don't understand why the power factor changes like that.
I don't know if that is normal or if the meter is fooling around.

Tried it on a light I have (40W bulb), said 0.2A / power factor 100
Then on my dyson fan :
off : 0.01A / PF 30
on : 0.2 / PF 70

Don't know if that helps. Again I have my doubts on that meter and I don't know if it can be trusted. Unfortunately I have no other mean to measure the actual current draw of the motor.

:yikes:

What ever you do, don't run the thing any more until you solve the problem. That is almost 3x the label plate current (7.3A)... it is drawing more current than a 5HP fully loaded motor.

200F? While the NEMA Class B Insulation is rated at 266F, I bet the internal temp of the motor is near or past the limit. Any additional operation is going to kill the motor... and probably start a fire. Fire extinguisher handy?

Do you have a phototach? Bet you the motor is NOT spinning at 1680 rpm.

I agree, that motor is drawing WAAAAY too many amps... and will self-destruct if you continue to run it.

I would send those amp ratings to Matt in another Email... This is definitive information.

OTOH: The wavy finish looks good!

 

[tino_ale]

Ok I got a chance to do the test I wanted and ran the motor free of any load. No belt, just the sheave on.
As before, the motor seem to run pretty free of any resistance by hand.

Started at room temperature 17°C. Used an IR temp device, at the middle of the motor body, underneath the casing (easiest access).
5 min : 35°C
10 min : 44°C
15 min : 56°C
20 min : 62°C
25 min : 69°C
30 min : 75°C
35 min : 79°C
40 min : 84°C
45 min : 88°C

I stopped there. It was pretty obvious where this was going, somewhere north of 90°C.

Matt replied to my request. He said he was sure the 50/60Hz difference would definitely NOT explain the issue I'm having. Motor are stamped 50 or 60Hz depending on where they are going to be sold, but they are the same.

He said he wasn't sure the free load test would mean much but I ran it anyway because it's an easy and repeatable data point.
He said he's not sure about the temperature.

What I need to know is if those temperature are a hard evidence that the motor is not running normally. Would someone with a PM1236 be kind enough to try the same test ?
Not on purpose but on occasion, next time you need to change the belt setting ?

BTW, running the motor in forward or reverse doesn't make any difference at all.

 

[John Hasler]

The current measurements you made previously suffice to conclude that the motor is defective.