# Small Electric Motors - Any Hope?



## TomKro (Aug 27, 2021)

Spent a little time checking out some old electric motors for a neighbor.  I put power to the motors to see if they're any good, but limited success.  One just hums, the others spin, but four of the motors show voltage on the cases under power.  




I opened up the junction boxes to look for wiring damage and shorts.  Lots of cruddy feed wiring, but I cleaned up the connections with ring terminals.  Nothing else obviously bad, but four cases still showing some voltage under power.   

Any idea what to check next?  Or off to the scrap pile?  Any benefit to splitting them open and digging deeper?

Sort of humorous (to me), one of the wiring diagrams indicates "UNGRND".  I guess that's the hot leg.  I have just enough electric background to be dangerous.  





Any guidance is appreciated.

TomKro


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## sdelivery (Aug 27, 2021)

I think you have pretty much done what you could ex cept the one that just hums. That one could be the start circuit and careful disassembly and cleaning could resolve that. Check the start capacitor as well.  That is probably a good one yet.


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## TomKro (Aug 27, 2021)

The one that hums is really old.  Constructed with some sort of oddball square end mounts, but no saddle to mount it.    

I'll probably open that one up purely out of curiosity. 

Thanks for the advice.  

TomKro


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## sdelivery (Aug 28, 2021)

Please take and post pictures reguardless of the results.


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## machPete99 (Aug 28, 2021)

Could be the start capacitors, which are typically in the bulging compartment on the outside.
Note that you should short the terminals before touching these as they can hold a charge if they are any good.


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## markba633csi (Aug 28, 2021)

The leakage to the case may be acceptable- You should check with an ohmmeter from both the power leads to the case- should measure higher than 1 meg ohm (1 million ohms) to be usable.  Of course you would also run a ground wire to the case for any of those, if you were to put them in service
-Mark


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## Ulma Doctor (Aug 28, 2021)

the best way to learn something about induction motors ,IMO, is to take one apart,
there will be no mystery as to what a motor is made of after that


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## TomKro (Aug 28, 2021)

Curiosity got the best of me.  Rainy saturday morning in Aberdeen. 

Took the cap off the little humming motor.  A bit of sawdust in there.  





Cleaned it up as best I could.  Used a point file on the contacts and some spray cleaner.




Looks as though three wires are creased and some broken insulation.  I sprayed a little "liquid tape" into a dish and painted on some insulation. Still no luck.  Motor didn't spin up, and I didn't keep the power on it long enough to check the case.  

Either the wires are frayed too much inside the insulation or maybe something is shorted in the windings (?).  I'm getting close to the limit of my abilities on this one.  Not sure if I can solder in new wires without making more of a mess.  

Gonna pack it up for now on this motor.  

As to the the other motors with hot cases, I'm going to have to acquire a better ohm meter.  Don't think I should trust my $10 multi-tester from Radio Shack.  Been bouncing around in a tool box for a few decades.  When I re-wired the feeds with ring terminals, I left the ground leads extra long.  Still a little hope for the four other motors, but fading fast...

Thanks for the help. 
TomKro


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## matthewsx (Aug 28, 2021)

Two words

fire hazard


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## TomKro (Aug 28, 2021)

Yep, that motor was pretty sad.  

BTW, I don't plan on relying on the painted on insulation for operation.  Mainly to find the cause of the hot case.  

It gets better.  Here's the "good" motor.  No sense using electrical tape when duct tape is handy...




The motor itself is actually pretty clean.  Power cord needs some TLC.

TomKro


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## Bi11Hudson (Aug 28, 2021)

Measuring from any conductor to the frame: The lower the resistance, the worse the leakage. Properly done with a "megger", any resistance reading below 500K is bad. But then a megger puts out much higher voltage than an ohmmeter, usually 500 volts. Such leakage cannot usually be repaired, it must be rewound. "Dipping & Baking" such motors is a valid repair technique, but usually is not worth the cost for smaller (<25 HP) motors.

It has been my experience that an "analog" ohmmeter gives better results than does a digital. There are circumstances where a digital meter will not show voltage when it is there. A good way to commit suicide. But rare in a "home shop" environment. But then, I have always used "high end" meters, a Fluke digital and a Simpson 260 analog. Your results may vary. . . 

There is a class of motors that uses different "impedance" windings to get the phase differential without using a capacitor. Usually relagated to fans and other "light" loads, larger versions _can_ be used for machine tools. These motors will still have a centrifugal switch. There is another class of motors that I haven't seen in a long time, ca. 1970ish. It has a commutator and brushes but there is a "shorting" ring that operates at speed and the brushes are "shorted" to each other. I bring it up because your project involves old motors.

There are many "jack leg" repairs made by "less than competant" repairmen where cord insulation has been damaged. Even at low (120V) voltage, if the insulation is damaged, replace it. There are some versions of "duct tape" that contain metallic fibers. Cheaper "duck tape" *usually* doesn't. In any case, *neither* is electrical insulation.

Using compressed air to remove sawdust and other contaminants from motors does a fair job. However, use the lowest pressure possible. My preference is ~15 pounds max. Lower is better. Washing with electrical solvent once the loose trash is blown out is an option. In any case, *do not use* line (~100 PSI) pressure.

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## TomKro (Aug 29, 2021)

Thanks for the info on insulation testing. 

I really can't justify an $500 multi-tester, but I do need to get something a lot better than what I have. 

I wasn't familiar with the Simpson brand.  Didn't realize they were still in production.  The last time I used one of those was in physics lab - a long, long time ago.   Maybe a lower cost Fluke in my future, but have to shop around.  

TomKro


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## Bi11Hudson (Aug 29, 2021)

A megger is one of those instruments that if you really have regular use for, they can be found. For the average "repairman" it would be a waste of money. I got lucky, my brother found one in a "yard sale" and knew I knew what it was. Otherwise, I would still be "meggerless".

A megger can be "sort of" simulated with a microwave transformer. It is fairly easy to "hi pot" with AC. The problem is dealing with the high voltage. You need a *good* meter with a high voltage range to start. And dealing with "one hand in a pocket" testing. I recommend against it unless the tester is well qualified. *It is dangerous*. Not just hazardous, serious danger. Like smoking while reloading shot shells dangerous. My suggestion is to find someone (motor shop?) with a megger and have them test it.

Now for Simpsons, I have a couple. But had them for years, one a Series 4, the other a Series 6. Most of the time I use the Series 4, it reads the higher voltage. The Series 6 is OSHA compliant. Backward plugs, flared probes, lower voltages, the whole shooting match. The Series 4 will measure 2300 volts with ease. I do advise "hot sticks" though.

It's been two or three years since I looked, but last time I went prowling, the Simpson was still out there. But as a Series 6, OSHA compliant. Or maybe Series 7 by now. For an earlier version, you would have to prowl used sites like eBay. The big deal about the Simpson is that they will withstand being dropped from preposterous heights. Like from the bridge crane in a mill. There are many meters that are the same sensitivity, just not as rugged. 20K ohms/volt is not _that_ sensitive. I have two or three other meters of similar sensitivity. I reach for the Simpson as much through force of habit as a need for "accuracy".

My digital is a Fluke 76. A 4 digit resolution for reading 4-20mA circuits. It also serves as a calibration meter (+1 order of magnatude) for the analog meters. I have a 4-1/2 digit (AmRel) but don't trust it. Last I looked, the Fluke was under a $100. I don't have need for a "cal lab" these days, but do like to stay reasonably accurate. FWIW, I use a digital to measure resistance. That way, I never have batteries in the analog meters.

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## Superburban (Aug 29, 2021)

Bi11Hudson said:


> The big deal about the Simpson is that they will withstand being dropped from preposterous heights. Like from the bridge crane in a mill. There are many meters that are the same sensitivity, just not as rugged. 20K ohms/volt is not _that_ sensitive.
> 
> .


My series 6prt (roll top) did not fare well after falling out of my trucks tool compartment, about 4 feet.The guts were still good, but he case did not survive. No I keep an old military TS-352 in the truck, the simpsons stay home.


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## mmcmdl (Aug 29, 2021)

Lots of older motors residing down here in Fallston Tom if you run out up there !  I haven't been down my late uncle's house in years , but from what I remember , he has half of the old Crown Cork and Seal plant out in his shed .


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## Bi11Hudson (Aug 30, 2021)

I suppose the truck was moving? I have dropped a Simpson 4 feet and there wasn't enough left to repair. And have dropped one from a crane that wasn't scratched. Maintenance men lead a hard life, things get broken. Then there's "Splinter", came rushing into my (instrument) shop and grabbed my Simpson. As I attempted to tell him it was a new meter, he gave me the "Boss-Flunkie" routine. And shortly used the Series 6 to (attempt to) measure 2300 volts on a synchronous motor. The high voltage(2500 volts) was taken off when they became OSHA compliant. When he finally got back to work after 2-3 weeks, some of his face was still bandaged. Seems the glass shattered too.
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## TomKro (Aug 30, 2021)

Still no decision as to what multi-meter to pick up, but now considering a more general purpose unit with a hoop ammeter.   The Depot has a few models from Klein tool.  It looks like some of these meters are marketed for HVAC work and can also check capacitance and temperature.  Might be handy for general purpose basement tinkering.  Any feedback on the Klein tool brand?

As to use of "meggers", it looks like most of these motors are headed for salvage.  I opened up a nicely built 1/4 HP split phase Westinghouse motor.  This one also performed double duty as a dust collector. 




The contacts for the starting windings were really burned up. The sheet metal broke apart while trying to scrape away the fried sawdust.  Hard to believe it started without smoking.   




TomKro


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## Bi11Hudson (Aug 31, 2021)

I have recovered motors in worse shape, but they were do or do without. Not something I would do as a pass time. 

Re. Klein Tools: Klein has been a point of reference as long as I have been an electrician.(1965) I'm sure they have been around longer but I don't have direct knowledge from childhood. An important point is that there are (at least) two versions. Those sold by electrical supply houses and those found at Home Depot or Lowes. The "low end" tools found at HD are still far better than off brand tools. The "high end" versions sold at supply houses are without compare. I had a pair of linesman pliers that after 17 years as a working tool would still cut a hair. They were burned when a noob told me the wire was dead. . . and it wasn't. The handles that come on new pliers are worthless. Good, thick, properly insulated covers are extra. A pain in the wazoo to install but well worth the effort. They are exceptionally good tools, but must be taken good care of. Throw them in a tool box and they rust. I have used mine every day from a pouch, never had a problem.

Re. Amprobes: There are Amprobes and then there are "clamp on ammeters". I place the Amprobe in the same class as Simpson and Klein. The rest are just "the rest". An *Amprobe is a magnetic device, not electronic.* The newer meters all claim a digital display, with batteries that can go dead when most needed. They depend on a "Hall Effect" device to operate. As with any meter, if it reads zero, check on a known good circuit to verify. I prefer an Amprobe mechanical meter to all the bells and whistles. There are some Amprobes that have a volt meter scale, I have one. But I've lost the leads somewhere along the line. Doesn't matter, I never used that function. That's what a Simpson is for.

*Amprobes are AC devices. They will not work on DC*. There are DC versions but are well above the cost even a professional would pay. Think "corporate tool room" costly. An Amprobe is calibrated to 60 cycles (hertz). Reading above or below that, there will be an error. There are probably 50 cy versions but I've never dealt with one. I have used the 60 cy version on 50 cy, it worked well enough to hook up the ship. The lowest scale is 5 amps (I think). If accuracy is needed below that, the conductor can be "looped", passing through the clamp two times, to double the current. 

DC current is better measured with a shunt. A Simpson can handle 200mA. Anything higher should use a resistor, measuring the voltage drop. A Simpson also is calibrated to read 60 cy in AC voltage. True RMS measurement for AC current or voltage is usually relagated to the instrument shop.

Shopping for a "multi-meter" for home use is a fuzzy area. Especially as they are used "on again-off again". The only "advice" I will offer is to have a separate VOM and Ammeter. An Amprobe is higher end but. . . For casual use, most any brand will do. Same as with a VOM. I don't like digital displays, but that's your call. For longevity, go with Amprobe analog. 

M Klein is deceased, the sons are probably long retired. Who knows who owns the name now. But be advised, they never made test instruments. That's a whole nuther ball of wax. Meaningless to meters.

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## TomKro (Aug 31, 2021)

Bi11Hudson - Thanks for all the advice.  You certainly have me reading the specs more carefully.  

Aside from the specs, I try to look carefully through user reviews.  Never sure how much to trust the reviews, but when I see a distribution of ratings skewed a bit at the low end, I tend to get more cautious. 

I'm definitely in the home use "fuzzy" area.  I don't expect to run into anything above 240V AC, and likely limited DC, but it's important to get a good understanding of the limitations of each style of device.  

Thanks again, 
TomKro


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## Weldingrod1 (Aug 31, 2021)

Honestly, having -any- multimeter is better than none... I mean, it's a tool, right? ;-)

That said, cheap multimeters are only suitable for small currents. Its VERY easy to blow the fuse for the current and not know it. Diagnosing.said fuse requires some knowledge. And, it's always a pain to get to.

Clamp on ammeters are fabulous! Analog ones are nice because of the complete lack of batteries! Digital will read a wider range.

DC and ac/dc reading clamp ons are not so expensive these days. There are two methods to make these work: hall effect sensing of the magnetic field value (low accuracy), and zero sensing. In the latter, the hall sensor is only used to find zero. Current is run through a winding on the clamp core and this is used to zero out the field. I actually built one many years ago 

Stay away from high voltage unless you know what you are doing. In this case, high should be interpreted as above "safe extra low voltage or 30ish Volts" for a total noob, and 120 volts for a small level of skill. For 120 you need to develop your "one hand measurement" technique. Clip leads are your friend here! It's best to install the meter and then power up. That way, you are well away if something goes bad.

On 120vac and up you really need to avoid having one lead in each hand. You, my friend, are a conductor! Your heart does not run right after passing current :-(

Ok, I'll stop now...

Sent from my SM-G892A using Tapatalk


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## hman (Aug 31, 2021)

@Bi11Hudson - Good point about the lowest scale on an Amprobe.  I get around this limitation when necessary with a homemade "gizmo."  It's some solid copper wire (I think 14 or 16 gauge) taken from Romex and a couple of cord caps.  One conductor is formed into a single loop, the other is looped around10 times.  And if nothing else, the gizmo lets me measure current without having to open up the DUT and separate out the conductors.


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## Bi11Hudson (Aug 31, 2021)

RE the preceding post: Somewhere I have a molded plastic adaptor for the same purpose. It's only 1:1 and 2 wire. From the old days before ground conductors. I like the pictured adaptor, but one should be careful with such a winding. At 50-60 cycles it wouldn't have any effect, but a high speed pulse could cause problems. Like lightening. . .

Sea Story alert. This really isn't relevant except from the perspective of safety. The difference between a fairy tale and a sea story? The fairy tale starts as "Once upon a time", the sea story starts as "This ain't no $#!t. I was there, I saw it"

I was working in an old rolling mill  built around 1920(~'86) with a 480 Volt "grounded delta" electrical system(grandfathered) and no cooling in the MCC.(Motor Control Center) Using a "Wiggington" type tester, I read zero(0) volts phase to phase on the buss bars. A rare occasion, I didn't test the Wiggie on a known good circuit. In a rush, the mill was freezing. . . My Wiggie had a broken lead. It was summer, the MCC was hot, I was sweaty. I grabbed the frame (C phase) and leaned in to reach between the buss bars. My right hand between the A Phase and B Phase buss bars, my left hand at ground, the C Phase. On normal "Wye" connected systems, Phase to Ground is 277 volts. On a grounded Delta system, Ground is the third phase. So I got 480 Volts Phase to Phase across the chest. (Across the heart) That knocked me back, into a live front 900 volts DC switchboard. I wasn't hung up, fell free. But still have the burn scars on my shoulder. *And best of all, I'm still alive to tell about it*. The "B" rate with me was scared I was dead. When I woke up, he was stark white and had thrown up.

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## hman (Aug 31, 2021)

You're absolutely right about the hazards of jury-rigged gizmos.  I ALWAYS check to see that the insulation around all the conductors is intact.  And as you can see, it's ONLY mean for 115 volts.  I've never had to deal with anything above 230VAC ... and damned happy about that.  Very happy to know that you survived, and are here to tell about it!


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## Bi11Hudson (Sep 1, 2021)

Thank you, Sir. Just another sea story, of which there are many over my lifespan. Get me wound up about "pre-OSHA" electrical systems, 2300 volts, 7200 volts, and 4160 volts where a motor is driven across the line. 480 was "low" voltage in those days. God is keeping me alive for His purposes. I don't worry about it too much.

You can thank Tommy Edison for the low voltages used for domestic systems. A 240 (220, 230, etc) volt system is only 120 volts to ground. It only becomes 240 when one gets across the two lines. Rare, but it can happen. That's *why a ground conductor is so important*. Even truck batteries, at 12 volts, can be dangerous. And 12 volt systems are well below OSHA standards. I had an uncle lost a finger when his wedding ring got across a battery. 120 volts is considered high voltage when the circumstances warrant. *120 volts can kill just as dead as 4160*. A good point to keep in mind.

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## TomKro (Sep 1, 2021)

Those sure are exciting work stories.  Glad you're still here too.  

My work hazards were limited to paper cuts and occasionally losing a big spreadsheet file.  Recently retired, so now I can tinker with old electric motors.  

Since Thomas Edison was mentioned, I have some pics of a very old GE motor for forum amusement.  This one I actually purchased without knowing the cast feet had been cut up.  It runs smooth, but unfortunately another hot case.  No obvious problems with the power cords, so maybe just insulation issues from moisture and time.   

Here's the nameplate:




When I opened it up, the only broken component was a small thrust washer.  In the pic you can see the cast foot that was chopped up for some remounting/repurpose.  




The windings in the frame cleaned up pretty easy.  Note the knot in the power line for strain relief. 




The rotor was interesting.  The tapered contacts on the left slide along the motor shaft (interior to the rotor windings) with some sort of weight disk on the right.  Not clear as to what provided the lateral forces to make/break the contacts.  Also, the case bolts were 1/4-20 with brass acorn nut ends.  Pretty heavy duty for a 1/4 HP motor.  I had to add a jam nut to back out one of the short case bolts that dead ended in the case.  




On one end cap was some sort of spring loaded brush control rocker plate.   Not clear to me if just for assembly, or if the sliding component on the rotor also backed off these brushes.  





Are there any antique motor repair folks out in H-M land? 

I doubt the feed wiring is causing the hot case.  Maybe someone could use some vintage parts?  

Hope you all enjoyed the historical hardware pics.  

TomKro


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## Bi11Hudson (Sep 2, 2021)

Another* Sea Story* for y'all. I've been up all night, couldn't sleep and just wanted to recount some of my experiences.

Background: the same mill as noted above. The furnaces (2) used 115KV to the plant, where it was reduced to 44KV. The 44KV crossed the plant to another transformer where the power was reduced to ~300 volts for the electrodes. I'm not real sure about the electrode voltage, that just sounds right. We're talking over 30 years ago. FWIW, I am not, and never have been a "High Voltage Lineman".

To put the arc furnaces in perspective, picture in your mind a Lincoln "Buzz Box" welder, a farm welder. Three of them, since it was 3 phase. The arc is adjusted by making arc length for each phase longer or shorter. Now picture the "rods", the electrodes as 14 inches diameter. They were toward the small end, USSteel used 18 inch electrodes. Bigger ladles. . .

I will admit up front the failure was my fault. I made a mistake and cost the company several days down time. In my defense, I had been working 84 hour weeks for a while. 7 -12s, no break, no relaxing time, get up, go to work, go home sleep, get up again. When the boss told me to open the switch, I opened the switch. High voltage, 115KV, uses an Oil Circuit Breaker where the contacts are covered with oil to prevent flash over. The disconnect is just that, not a control device, just a way to ensure the circuit is dead. The OCB is supposed to handle loading and unloading the circuit. The disconnect just isolates.

There had been a miscommunication between my boss and the production foreman. Both of the furnaces were running flat out, called a "flat bath" where the ladle was melted and temperature was being brought up. Boss told me to open the switch, I opened the "disconnect" without opening the OCB. Those 84 hour weeks caught up with me. At near full load, when the jacks opened, they arced across. And continued to arc for nearly a minute. At the time, it felt more like 2 hours. The jacks were originally some seven feet long. By the time the arc cut out, they were only about three feet. All I could do was hunker down and pull my collar up to prevent the sparks from getting in my clothes. Shut down the plant for 3-4 days while the power company repaired the switch. Me? I was just numb. There was no disciplinary action taken, I didn't even get chewed out.
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