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Generators & Motors General Discussion

No Output Old Dayton 3K Alternator


I have an old Dayton 3K alternator, model 3W178C, that has no output. The rectifier, p/n...

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  #1  
Old 09-20-2010, 01:30 PM
larry3754 larry3754 is offline
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Default No Output Old Dayton 3K Alternator

I have an old Dayton 3K alternator, model 3W178C, that has no output. The rectifier, p/n 21828-000, is shorted and is obsolete and not available from Grainger anymore. I don't have the manual or schematics for it either. I need some specs on the rectifier so that I can replicate it with diodes from Radio Shack, etc. It is a three terminal potted rectifier which indicates only two diodes and possibly a limiting resister contained in the potted module. Any help would be appreciated with specs or diagrams.
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Old 09-20-2010, 02:19 PM
armandh armandh is offline
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Default Re: No Output Old Dayton 3K Alternator

it might also be a 4 diode bridge with the case as minus

if a two diode bridge then the winding feeding it is CT [easy to test]

a common 4 diode bridge will work for a 2 by not using the minus or plus terminal depending which is desired
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Old 09-20-2010, 02:58 PM
larry3754 larry3754 is offline
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Default Re: No Output Old Dayton 3K Alternator

The module case is not electrically connected to the diodes. Infinite resistance. I'm looking for info concerning the amperage of the diodes. Then, I can get purchase them from radio shack or someone else and duplicate the original rectifier hopefully.
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Old 09-20-2010, 03:01 PM
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Talking Re: No Output Old Dayton 3K Alternator

I replaced the one in mine, by using a 10 amp Bridge and only using The Positive Terminal for the Output. It is still making power 15 years later. I assume yours is a 2 Pole Genend. (3600 Rpm)
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Old 09-20-2010, 06:48 PM
K D Redd K D Redd is offline
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Default Re: No Output Old Dayton 3K Alternator

What BTPOST said. When I use only 1/2 of a bridge rectifier brick to fix a generator, I cut the negative terminal from the bridge so there would not be ant wire confusion.
If you will read the resistance of the ac input wires that go to the diode block, you will find the other ends are grounded. This make the circuit look a lot like a full wave transformer power supply with a grounded center tap and two diodes.

Kent
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Old 09-20-2010, 09:20 PM
larry3754 larry3754 is offline
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Default Re: No Output Old Dayton 3K Alternator

I got a manual Emailed today from Grainger. I can see that the exciter coil is center tapped with it connected to the rotor minus brush and the positive output of the rectifier connected to the positive rotor brush. Schematic does not provide any diode specs. Just not sure what amperage diodes/bridge to select. May start with two 1N5404's, 3amp 400 PIV (since they are cheap, $1.59 a pair at radio Shack) and if they overheat,then proceed to a higher amperage. Any advice on amperage??
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Old 09-21-2010, 08:39 AM
K D Redd K D Redd is offline
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Default Re: No Output Old Dayton 3K Alternator

I like using half of a bridge rectifier package as when you mount it to the generator frame, the frame acts as a heat sink.

Kent
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Old 09-21-2010, 09:30 AM
Arkie Arkie is offline
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Default Re: No Output Old Dayton 3K Alternator

I would suggest AT LEAST 6 amp diodes and 10 amp would be ideal!
When you get ready to make a test run measure the DC current going to the rotor and I really like to use silcon diodes rated at twice their load current to help keep heating them to a minimum!

Also check the resistance of the rotor! A shorted or bad rotor will wipe out the rectifier! I would also use a temporary 10 amp fuse in the pos output to the brush when first testing! (this will help keep the smoke in the bridge)
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Old 09-21-2010, 09:45 AM
larry3754 larry3754 is offline
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Default Re: No Output Old Dayton 3K Alternator

Sounds good. I can get a 8A/400V bridge at Radio Shack for $2.59. I will post my results when available.

Thanks Again,
Larry
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Old 09-21-2010, 10:29 AM
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Default No Output Old Dayton 3K Alternator

Here is a link I happened to have saved for manuals for small ac gen's!
This manual shows yours listed! (in case you need to get deeper into, etc)

By shopping and google searching, sometimes you can find these manuals used, etc for less $$'s! (also try Barnes and Noble's used books)

http://www.themotorbookstore.com/smalacgenser.html
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Old 09-22-2010, 05:43 PM
larry3754 larry3754 is offline
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Default Re: No Output Old Dayton 3K Alternator

Installed rectifier and tempory fuse. Cheched output voltage and it was about 80 VAC. Checked frequency and it was only around 40hz. Increased throttle adjustment until output frequency was 60hz. Then, output voltage was 130VAC without any load. Voltage dropped to 118VAC with a drill motor as a load. It appears to be working OK for an old unit without a voltage regulator. However, wouln't use it to power any of my sensitive electronic equipment.

Thanks for everyone's help,
Larry
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Old 09-22-2010, 10:36 PM
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Default Re: No Output Old Dayton 3K Alternator

I found some that are a little more expensive ($6.99 + shipping), but are rated 35 Amps @ 1000 Volts:
https://www.surpluscenter.com/item.a...-1206&catname=
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Old 09-23-2010, 08:00 AM
armandh armandh is offline
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Default Re: No Output Old Dayton 3K Alternator

if the voltage stays put between a few watts of load and almost full load the voltage is regulated.
it is just the method that is not obvious,
but over speed will run the voltage up and blow stuff up.
blew up my brother in laws cable box that way.

for years I used a coleman 5KW to get through power outages

thanks again john for fixing the burnt exhaust valve.

had no trouble running anything with in the load range
until I burnt the valve.

running too lean the extra O2 starts looking for something hot to oxidize.

one gets what one pays for when buying hardware store generators.
and I dont set it that lean anymore

Last edited by armandh; 09-23-2010 at 08:09 AM.
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Old 09-23-2010, 10:13 AM
Arkie Arkie is offline
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Default Re: No Output Old Dayton 3K Alternator

Quote:
Originally Posted by John Newman, Jr. View Post
I found some that are a little more expensive ($6.99 + shipping), but are rated 35 Amps @ 1000 Volts:
https://www.surpluscenter.com/item.a...-1206&catname=

John: Thanks for the surplus info link!

They have lots of stuff priced with-in reason!

Arkie
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