Doerr 6 HP motor problem

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  #1  
Old 05-06-15, 06:48 AM
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Doerr 6 HP motor problem

I have an Air Power (by DeVillbiss) air compressor, Mod LV660. While running it suddenly stopped. Power is getting to the motor, but it does not run. There is no sound from it either. It is a Capacitor Start - Capacitor Run 220V motor.

I find no info on this motor from any source, and cannot even identify the capacitor values. I would suspect the Start capacitor, but there isn't any 'hum' from the motor as is always stated when it is bad. The motor was 'purring' along perfectly, and just suddenly stopped before fully charging the air tank.

Does anyone have knowledge of the values of the capacitors, or any suggestions as to what needs further checking?
 
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Old 05-06-15, 07:00 AM
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Power is getting to the motor
How did you determine that?
 
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Old 05-06-15, 07:01 AM
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The values will be on the cap itself. You can do a simple check like to test it: https://www.youtube.com/watch?v=iRt9WYK1wdQ

Did you check for voltage at the motor or just at the pressure switch?
 
  #4  
Old 05-06-15, 07:41 AM
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I checked it from the breaker box, all the way through, and to the motor terminals.
 
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Old 05-06-15, 07:47 AM
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Checked with a Simpson meter. 220V present at motor terminals. (I am a Federally licensed 1st Class radio communications tech.)
 
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Old 05-06-15, 07:54 AM
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"The values will be on the cap itself."

Now, that would be 'normal'. However, no values are on either Cap. Instead there are just part numbers, and voltage. 'IF' that particular motor was still made I could just look up the part numbers or specs to get the values. There are just too many possibilities for the values on the different compressors. If all ran about the same area values I could sub some test values. However, I find that the Run caps on some are less than 65 uf, while on others it must be from 165 uf and up. The same types of variables holds for the Start caps as well.
 
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Old 05-06-15, 08:31 AM
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Did you try testing the cap as shown in the video?

Since the motor is not making any noise I think you have a broken connection in the motor someplace. It could be in one of the windings.
 
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Old 05-06-15, 08:38 AM
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It got too late last night when I was checking for the values, so I have yet to test the caps. I will be doing that after a doctors appointment. I haven't watched the vid, but I do know how to test them. I wish I still had all my shop test equipment I used to have when in business as I had a darn good piece of equipment just for caps. Now, I am back to just an ohm meter for that. I still have my spectrum analyzer, and several other of my radio test equipment yet. They just won't do much good with the caps.
 
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Old 05-06-15, 08:43 AM
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"I think you have a broken connection in the motor someplace."

I have wondered that also. I figured to check the caps first, and since they are old, getting new, but without the proper values I am stymied on that. I had figured on pulling down the motor to clean it and check it out fully, but late night, and no values for the caps stopped my progress at the time.
 
  #10  
Old 05-06-15, 11:44 AM
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You could always try contacting the engineering department at the manufacturer.

Nidec Corporation | Nidec Corporation
 
  #11  
Old 05-06-15, 06:04 PM
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That would be a good idea IF the company had a method to do so. They don't on this older compressor. DeVillbiss made their own motors, and pumps originally. When mine was made they had sold out to Emerson, which located in China. Mine was one that the pump, and motor were contracted, so there is no manual, or manufacturer resource to contact today.

Compressors are still being made with the name, but with the two companies involved today there is nothing even remotely similar to mine. Doerr isn't even Doerr any longer, plus the motors made are either 5 HP, or 7 1/2 HP. No 6 HP motors. They aren't even close to mine.
 
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Old 05-06-15, 06:19 PM
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If this motor has indeed failed I'm sure you be able to find a replacement. May not be the same HP, but at least one that will work. It just might be a bit pricey. Otherwise if you can't, a motor shop should be able to rewind it.
 
  #13  
Old 05-06-15, 10:35 PM
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I am hoping that it isn't the motor. Cap Start-Cap Run motors are always 'pricey'. The HP isn't the critical issue, you are right.

I had to spend all day with my wife at the Cancer Center, so I have not yet been able to check the caps, or pull the motor off for testing. Unfortunately, I do believe it possible that a winding broke, or burned through to shut it down. Usually, when a motor just stops working suddenly, and with no warning, it is something simple, and an 'open' in the visible wiring. With my luck I will probably find an open wire in the windings. We do have a good motor rebuilder here. I just hope
it doesn't come to that.
 
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Old 05-07-15, 07:47 AM
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I had to spend all day with my wife at the Cancer Center,
I'm sorry to hear that, stay strong and take care. (From another cancer survivor)
 
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Old 05-07-15, 04:07 PM
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That would be a good idea IF the company had a method to do so. They don't on this older compressor. DeVillbiss made their own motors, and pumps originally. When mine was made they had sold out to Emerson, which located in China. Mine was one that the pump, and motor were contracted, so there is no manual, or manufacturer resource to contact today.
You titled the thread "Doerr 6 HP Motor Problem. Emerson bought Doerr Electric from Grainger in 1986 and closed their Cedarburg, WI plant and intergated the Doerr manufacturing into the existing Emerson Motor plants. The engineering stayed with the Emerson Motor Engineering in St. Louis. In 2010 Emerson sold their electric motor business to Nidec of Japan. The Nidec USA engineering continues in the same building that Nidec now leases from Emerson at their Headquarters in St. Louis. Emerson never moved to China. The picture at the link I provided is the Emerson Motor Technology Center, now Nidec USA since 2010, in St. Louis. This is where Doerr engineering happens, but it has been rolled into the specialty motor business.
 
  #16  
Old 05-08-15, 10:22 AM
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Hi Joe, I had looked into Nidec before. (I goofed when I stated China. I had forgotten and ended up typing China instead of checking all my notations on what I had found. Including the proper sequence of takeovers.) I had found a couple of compressor motors on their site, and even sent a message as to my question. I have yet to hear anything from them, even in an online chat window. What I did find was that to buy one of their motors the cost is higher than buying a whole new compressor today by two to four hundred dollars. (Depending upon single stage, or two stage.)

I 'might' get time today to tear the motor down to run some tests. At least, I hope to. Again,
though, I would still want to know about the proper capacitor values, rather than 'guess-n-test'.
That method is ok, and can work well on other electronic equipment, but for motors with Start,
and Run caps it is not the best idea.

Dave.
 
  #17  
Old 05-08-15, 07:47 PM
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Why don't you just call them. The phone number is (314) 595-8000.
 
  #18  
Old 05-27-15, 04:25 PM
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I did try calling. That didn't get me anywhere so I finally sent an email
to the company that took over the Doerr motors. (U. S. Motors; a
brand of the Nidec company, but separate.) It took a while, but all I
got back then was an email that said the Doerr motors are obsolete,
and that they can no longer pull out any data on them.

Now, what I did find was that the motor was packed with black soot.
Everything was caked inside. I cleaned it out well, and metered out
all the windings, and connections. When clean, and the caps checked
the motor looked good, inside, and out.

I hooked it up today, but now I can't get it to run. I do get it to start,
but it kicks out immediately. With all the wires in the motor the same
color, could I have connected the start capacitor wrong? I have tried
every combination (just in case) with the two 110 V leads, but it just
starts, then kicks out.

Ideas?

Dave.
 
  #19  
Old 05-27-15, 05:53 PM
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While you had the motor apart did you check that the centrifugal actuator would slide on the shaft easily, that the spring(s) were intact and seemed okay, that the actuator would physically and electrically open the starting switch contacts and that the wiring to that switch was intact and did not have any worn insulation?

You will need to carefully measure the resistance of the two windings. You need to actually attach the ohmmeter leads to the wires, not just touch them because you need a stable reading on the ohmmeter and it WILL be a low reading. Do this with both windings and the one with the lower resistance will be the starting winding. While you are at it check each winding end for resistance to the other winding as well as to the motor frame. Anything but infinite resistance to these last tests means that you have either a coil-to-coil short circuit or a coil-to-case short circuit. Note that these could be either very high or very low resistances so measure carefully.

The running winding gets connected across the line supply. The starting winding will be connected in series with the starting capacitor and the starting switch and this combination connected across the line. The action upon starting is a flow through the running winding from one supply lead to the other; and a flow through the series of the starting winding, the capacitor and the starting switch back to the other side of the supply. When the motor achieves about 80% or more of the terminal speed the centrifugal actuator will open the starting switch and remove the starting winding and capacitor from the circuit.

Note also that the "quick and dirty" method of checking the capacitor given in this thread does NOT check the actual value of the capacitor. It is possible the value has drifted too low to properly accelerate to motor to the 80% needed for it to "lock in" to the frequency.
 
  #20  
Old 05-27-15, 11:51 PM
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Hi Furd,
Now, this is all something I can understand. With no schematic on the motor, and no
other type of technical data, I have been somewhat at a loss, and have had to move
very slowly in checking anything.

First off, I did have the capacitor wrong. When I got that right the motor would start.
However, when connected to the compressor pump the motor will struggle, and at times
stop, but while still trying to work.

Yes, the springs were good, and the actuator slides ok on the shaft. The actuator
worked ok manually. All wires looked good (even new looking). I cleaned the contact
points well also.

I will go through the windings again. Of course, at the time I was just looking for
opens, or short to the frame. I'll use the Simpson again as I just can't see the
LCD of the Fluke well enough. Not even the red LED on the ole Sencore is good
enough for these ole eyes.

BTW, I did find the values for the Start and the Run capacitors. I just wish I
had not sold my equipment to actually test them to see if they had lost it.

Thanks,
Dave.
 
  #21  
Old 05-28-15, 12:43 AM
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I hear you about giving away test equipment. I had a capacitor bridge with a calibrated scale and "magic eye" tube that I rarely used so I gave it to a man for his Museum of Obsolete Technology (MOOT). Of course after it was gone I found I could really use it. Coincidentally, this man's name is also David.

Anyway, as I am sure you know, the larger capacitor is for the starting and the smaller one for running. I didn't remember (or you didn't state, I'm too lazy to re-read the entire thread) this being a capacitor start-capacitor run motor. I've been away from motor repair far too long (decades) to remember how a run capacitor is even wired to a single phase motor so I am of no help there.

I suspect that you also know that checking the insulation resistance (coil to case) is best done using a megohmmeter (Megger) but I doubt that you have one in your back pocket. Turn-to-turn shorts are the worst as they are almost impossible to find with conventional testing gear. They rarely show up even with a Megger test but they will have a decided effect on the power of the motor and also cause it to run hot.

I wish I could be of more help but that's all I have. I wish you luck.

I just skimmed through from the first post. In that initial post you stated it was a "220 volt motor but in this recent post you state,
"I have tried every combination (just in case) with the two 110 V leads, but it just starts, then kicks out."
When you state "the two 110 V leads" do you mean you are using 120 volts from line and neutral? (Residential voltages are 240 and 120 and have been for at least fifty years) or are you confusing the issue thinking that a 240 line is made up from two 120 volt lines (it isn't)? A 240 (220) volt motor will NOT run on 120 volts and be able to deliver any power.
 
  #22  
Old 05-28-15, 12:57 AM
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I was thinking that in a capacitor start-capacitor run motor the run capacitor was connected with the starting winding and line with the starting capacitor connected in parallel with the run capacitor through the centrifugal switch. I did a Google and indeed that is the correct connection. Here is a diagram:

[ATTACH=CONFIG]51212[/ATTACH]
(Image courtesy of simplecircuitdiagram.com)
 
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