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Generators & Electric Motors General Discussion Antique Generators and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Electric Motors General Discussion

re-energizing test failed


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  #1  
Old 04-29-2003, 10:13:28 PM
Gary Koleno
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Default re-energizing test failed

Just a follow up on the thread of re-energizing dead generators. I built up a light cord set per the instructions in the document below - - followed instructions to a "T", and it didn't work.Looks like I'll have to find a way to access the fields,and flash them with DC. The problem is this generator is one of those cheap units with no way to to reach the rotating field while the generator is assembled. What next?? The break down parts drawing shows the slip rings inside of the main body of the stator housing ,and the end is concealed by the fan assembly.Its a Sears model number 580.324050 - 2000 watt. There has to be a way to do this with out a major amount of work!! Comments anyone ??




http://www.endtimesreport.com/dead_gen.html
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  #2  
Old 04-29-2003, 11:39:08 PM
Franz
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Default Re: re-energizing test failed

Disassemble the machine far enough to access the brush holders. Attach a wire to each brush holder, and route to the control panel, or outside of the machine. Reassemble the machine. Start engine, and flash the set. Now, it will be real easy to flash it the next time you need to, and there will be a next time.
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  #3  
Old 04-30-2003, 12:49:02 AM
Gary Koleno
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Default Re: re-energizing test failed

Thanks Franz - - How do I identify the The plus & minus terminals to keep the correct polarity, or doesn't it matter ? Are the brush terminals marked in any way? - - -Best regards: Gary.
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  #4  
Old 04-30-2003, 12:22:29 PM
Franz
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Default Re: re-energizing test failed

Since I'm not looking at the unit, or the paperwork, it's a bit hard to answer. There should be some indication on the brush holders, or on the paperwork.
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  #5  
Old 05-31-2003, 02:49:22 AM
Gary Koleno
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Default Re: re-energizing test failed

Franz - -I finally got back to working on this problem generator again. I took measurments of the location of the brush holders,and cut a 1.25 inch hole thru the case exactly above the brush holders. Now I can access the brush screws easily while the machine is running,and snap a plastic cap over the hole after done. There are no markings on the holders for + or -, but the wires are red and black.Using Red as positive, I flashed the field using a good 12v tractor battery. At the same time I had a 100 watt trouble light plugged into the output on the generator. No output was seen during the flashing or after. I only get a "ac" reading of 3.5 to 4.1 volts at the output ac sockets.

Every thing else looks good, no shorts to ground on the rotor and stator assy's. Continuity on all windings and clean slip rings. The only other thing is the "rectifier assy" which will un-plug like a sealed relay in a connector.I don't know if that is good or defective. Even if the rectifer assy is bad - - wouldn't the generator produce some output during a external excitation of the rotor while running? The red and black brush wires go into the rectifer connector and a pair of black wires come out of the connector and go into the wire harness to the stator? I'am at a loss at this point, Hate to put out $40 bucks for a new rectifier assy, if the old one is good. I don't have any idea whats in the sealed rectifier pkg, and don't have a schematic to go by,so I'am guessing on what to try next.--Any suggestions?
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  #6  
Old 05-31-2003, 07:48:07 AM
Steve Wright
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Default Re: re-energizing test failed

It acts like shorted diode (rectifier)to me. AC goes in on your black leads and comes out DC on your red and black. I could easily test it if it was here and I could see it. You possibly could make up your own rectifier with a diode bridge rectifier for a couple bucks and try it. They are just four terminals, 2 marked AC usually with a sine wave symbol (like an S laying down, then the other 2 terminals are + & -. Get one at Radio Schack or out of someones junk box. My opinion. I always hope I am right when I type this up. I could even send you a bridge out of my junk box for the test. Steve
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  #7  
Old 05-31-2003, 10:56:48 AM
Matt Fretwell
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Default Re: re-energizing test failed

Hello Gary,

To check to see if the rectifier has a short, just test between all the connections on the rectifier unit with you meter on the ohms range, (whilst out of circuit). This will let you know if its internally shorted.

Matt.
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  #8  
Old 05-31-2003, 12:03:25 PM
Franz
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Default Re: re-energizing test failed

Gary, if I were playing with that machine, I'd go at it this way~ Remove the rectifier (bridge) With machine running, Apply 12 volts DC thru a limiting resistor (Backup light bulb) Check for AC coming from the 2 black wires that go to the Bridge. Check for AC coming from the output. Your voltages at output probably won't be right, but you should see AC at both points with the battery in place, if the problem is in the bridge. Some machines will reenergize instantly with flashing, and others will need to run a couple minutes with external DC applied to get their act together. If you make AC with the battery exciting the rotor, chances are the bridge is the offending item.
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  #9  
Old 05-31-2003, 09:08:55 PM
Gary Koleno
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Default Re: re-energizing test failed

Thanks "everyone" for the quick response. I will consider each of your suggestions toward my next step. Will have to wait a day or two for the wet weather and high winds to settle down.I play outside while running this machine,and don't want to get zapped. In the mean time I'll pull the rectifier pack out and run the suggested test,and possible repair per your directions. Thanks again everyone - -I'll post my findings to keep you informed. "Best Regards": Gary.
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  #10  
Old 06-04-2003, 02:52:17 AM
Gary Koleno
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Default Re: re-energizing test failed

Pulled the rectifier package out of the generator today. After testing the pins - - it appeared shorted on the ac terminals. I then dug the potting away from the components and found "five" components total. There are "four" diode's,forming a bridge rectifier. They are unmarked, except for the band at the cathode end.(they are about the size of one watt resistors). The fifth is a device across the "DC" end that I don't know what it is or its function. It looks like a disk about 1/2 inch in diameter,approx. 1/8th inch thick. Leads out of the center on each side,one going to the +, and one going to the - terminal of the output.It is color coded silver,orange, aqua(green?),and red.(stripe's across the flat surface) - -no polarity shown on this device.

I would like to replace the diode's from Radio Shack stock. What size (current capacity)and voltage should I use? Don't know how to check the disk - -I get a 670 ohm reading one way and nothing the reverse direction. this is while still soldered in with all the diodes.And the meter in the "Diode test mode" Still learning here, all advice is welcome. Best regards: Gary.
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  #11  
Old 06-05-2003, 01:14:00 PM
Matt Fretwell
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Default Re: re-energizing test failed

Gary,

What is the rated d.c output of the generator? The 670 reading that you are getting across the disc is the voltage drop of the diodes, which is normal. The disc is probably just a cap or cutout of some description. Unless that is reading short, it should be okay.
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  #12  
Old 06-05-2003, 03:39:08 PM
Gary Koleno
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Default Re: re-energizing test failed

Hi Matt - - - The unit in question is a 2000 watt AC alternator. Sears model 580324050. It belongs to a friend that had it for a long time, and hasn't put many hours on it. It looks like brand new - - not even dust in the alternator, cooling fan, brush holders etc. However it looks like I have two shorted, and one open diode in the so called rectifier pkg. I want to rebuild a bridge or purchase a bridge from radio shack,that will carry the alternator at full load. I'am looking for some advice on the bridge current and voltage rating required to do this. 5amp?,10amp? and nominal AC voltage device? Etc. The ready made bridge with wire leads may be the way to go? I have plenty of room, even using individual diode's for the finished pkg to plug back in the connector. Best regards: Gary.
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  #13  
Old 06-05-2003, 05:33:39 PM
Franz
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Default Re: re-energizing test failed

Gary, before getting into rebuilding the bridge, you should excite the unit with a seperate source and determine if there are other problems. If the bridge AC input was generated by a seperate winding, remote excitation will confirm that is good. You will also be able to determine if the output winding and field are good. While the bridge may be the problem, it ain't going to do a damb bit of good to rebuild the bridge only to find there is another problem. The bridge itself is probably nothing more than a 3 amp bridge package with a regulator across the output, and plenty of them are available. The regulator may be an oddball. I wouldn't worry about the bridge till I confirmed everything else was working properly. If you have a variac and 4 diodes you can fully confirm the machine's windings. If you have to excite with a battery, the only problem will be that your output voltages aren't correct.
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  #14  
Old 06-05-2003, 08:13:18 PM
Matt Fretwell
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Default Re: re-energizing test failed

Gary, If there aren't any other problems after you have checked what Franz mentioned, BY228 diodes(5A rating), or a full wave bridge rectifier package, as used in various psu's, will do the job fine. The diodes will only cost a couple of pounds at most. Matt.
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  #15  
Old 06-05-2003, 08:23:04 PM
Frank D
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Default Re: re-energizing test failed

Power Tronics INC Has some great trouble shooting info on there site including plans for a test set. Flashing instructions, and more good stuff

Here are the plans http://www.power-tronics.com/help%20files/testsetpg.htm Here is other info http://www.power-tronics.com/company%20info/technicalhelp.htm

and

http://www.power-tronics.com/technical%20page/Other%20Information.htm

Frank




plans for test set
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  #16  
Old 06-05-2003, 10:19:35 PM
Kid Dynamo
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Default Re: re-energizing test failed

That's a good website for generator info !

I wonder if that 120-240 Z wiring diagram would be the ticket for some of the guys who are looking to rewire their 3 phase units to put out single phase.

I guess if the generator has 12 leads and the coil leads are numbered the same it would work. Maybe...... I think......

My Grandpa refered to the first test run as the smoke test !!
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  #17  
Old 06-06-2003, 01:09:09 AM
Franz
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Default Re: re-energizing test failed

Been scratching my head and ponderin on that for a couple hours myself, and as memory doesn't serve me as well as it used to, I need to get ahold of a buddy of mine from Cat for a good answer. As I recall, it works on some machines, and not on others because of the way the stators are wound. A, B, and C coils are laid into the frame 120 degrees apart mechanicly in a 3 phase machine, so when you conncet them in the Z configuration, there is a certain amount of magnetic flux interaction. There is also a derating factor involved in the Z configuration. I've seen a number of people over the last 40 years who insisted on delivering single phase power from 3 phase machines, and have yet to see a load that could not be split up and spread across all 3 phases. Of course, that never stopped an endineer or archetect from writing a specification.
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  #18  
Old 06-06-2003, 02:44:23 AM
Howard Yoshida
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Default Re: re-energizing test failed

"It looks like a disk about

1/2 inch in diameter,approx. 1/8th inch thick. Leads out of the center

on each side,one going to the +, and one going to the - terminal of the

output."

This sounds like a varistor used to suppress voltage spikes. Hope this helps.

Mahalo, Howard
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  #19  
Old 06-06-2003, 06:32:35 PM
Gary Koleno
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Default Re: re-energizing is success !!

Thanks to everyones input - - I got this unit running at full output. Voltage is right on and frequency is as expected with various loads. The problem was indeed the rectifier package. I rebuilt it using individual diodes from Radio Shack. However I did follow the advice of Franz by doing further checks for ac output with external excitation - - before plugging in the rebuilt rectifier pkg. Thanks to all for your contributions to this thread, and a "BIG THANKS TO HARRY" for this wonderful site!! Sorry it ran so long,but I did get a great education from great teachers. "Best regards" to all - - Gary
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  #20  
Old 06-06-2003, 09:53:19 PM
Franz
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Default Re: re-energizing is success !!

Well gary, you've been a good student, and reported your findings accurately, so you'll get a good grade for the project. Hey, every once in a while we get one right.
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