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Hank F.
Hank F., Technician
Category: Small Engine
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Experience:  Certified on Onan and Generac generators
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Resistance Table for Stator on a 030426-0 BRiggs and stratton

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Resistance Table for Stator on a 030426-0 BRiggs and stratton generator. The book 87971 does not carry my model. I get 00.6 ohms on the #11 and #22 power winding. Is this a bad stator?

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This is a bit high, but should not be high enough to be an issue.

This part of this stator should be OK.

 

 

Customer: replied 6 years ago.

the excitation winding has "0" resisitance. i get absolutly no continuity when checking. the excitation wires are #2 Red and #6 Blue. THe excitation winding is importain in voltage creation as well Correct ?

COuld this be a bad excitaion winding which would be the root Cause ?

YOur gonna have to give me a more better awnser. " more detaiL"

Not a problem at all, my friend.

I can provide you with as much detail as you wish - but I will also need a bit more.

 

Exactly what is or isn't your genset doing?

Too much voltage, too little voltage, no voltage at all?

 

The DPE winding (excitation) is definitely needed for voltage production.

Here is a brief overview of how your set produces voltage.

 

A genset is composed of 2 major components - an engine and a generator, commonly referred to as an alternator. hf

A generator is composed of 2 major components - a rotor, commonly referred to as an armature, and a stator. The stator typically has 2 or more windings - 1 or more power windings, and a smaller exciter winding.

There are 3 things required for the production of electricity - a magnetic field, a conductor (wire), and movement between the field and conductor. Since the field has no physical mass, it is much easier to move it than to move the conductor. We move the field by spinning it with the engine. This is why most gensets are known as revolving field gensets.hf

When you start the engine, the rotor starts spinning (it is connected directly to the crankshaft of the engine).

The rotor is a giant electromagnet.

When not running, the rotor retains a small bit of magnetism, known as residual magnetism.

As it spins, the magnetic field around the rotor is passed through the windings of the stator (conductor). The magnetic field aligns the electrons in the wire and makes them move. This flow of electrons is electricity.

However, the amount of electricity flowing is not very much, so the voltage regulator takes the AC power coming in from the DPE winding and converts it to a DC current, and feeds it back to the rotor through the brushes. This increases the strength of the magnetic field - which, in turn, increases the amount of electricity produced - until the VR senses that there is 120 volts (give or take) available.

Remember, a magnet has 2 poles - north and south, or positive and negative. As the positive pole passes the windings, it moves the electrons in one direction (the positive pulse). As the negative pole passes by, it moves the electrons in the opposite direction (the negative pulse). One positive pulse and one negative pulse are one cycle, or Hertz. Since US power is 60 Hz, this process must happen 60 times per second (50 times per second (50 Hz) in much of the world).hf

We now have nominal voltage flowing (120 V in the US).

When a load is applied to the genset, this voltage drops correspondingly to the size of the load.

The voltage regulator senses this power drop from the exciter winding and says ‘Hey, I've got a load on and the power is dropping. I'd better make more power'. It does this by increasing the DC voltage to the rotor, which creates a stronger magnetic field, which pushes even more electrons into movement.

The VR constantly monitors this voltage and adjusts the field accordingly.

We now have electricity.hf

 

From what you are describing here, it sounds as if your DPE winding is bad, and that the windings of the stator may be shorted together.

Is the reading of the DPE winding actually 0 (no resistance), or open (no continuity)?

 

Another quick test of the stator is to remove all leads from the stator, and isolate them so they can not touch each other. Also disconnect all wires from the VR.

Set your meter to ohms, on the lowest scale possible.

Test each winding -

Main power 1 (wires 11 and 22) should actually be 0.16 - 0.19 ohms

Main power 2 (wires 33 and 44) should be the same

DPE winding should be 2.01 - 2.39 ohms

 

Now test one wire of each winding to ground - there should be no continuity on any of them.

Now test one wire from each winding to one wire of the other windings - none of them should show any continuity.

If you show ground or continuity between any windings, the stator is shorted.

If these are good, but the DPE is open, the stator is burnt.

This stator will run you over $500 - so be sure to test carefully.

 

If all of these are good, ohm across the slip rings of the rotor - it should read 7.7 - 9.6 ohms.

 

Customer: replied 6 years ago.

I know a good bit about elec. for my age. I have an A.A.S. Degree in Elec. Yes all wires are isolated regulator is off.


Story behind generator is that it is always ! under a substantial load! generator was producing one day and then nothing. "no power tools would work then"

 

The generator will produce 2.8-3 VAC and 5.8-6.0 VAC on the 240 volt side.


Rotor = 18.5 ohms, Stator= #2 & #6 DPE "nothing NO continuity"

Wire 11 and 22 00.6 ohms. thats all the wires coming out the end of the generator. the harness comes out same end, (i do have schamtics, just no values) when i probe the #44 and #33 i get 00.6 ohms. i have NO windings to ground.

 

Visual of the rotor windings is not a bright copper winding. I use to work in a motor repair shop. The stator is not as dark as the rotor it appears.

 

So these are the readings i have. I may try manually injecting 12VDC this saturday for fun and learning for my own benefit.

 

Too high resistance for Rotor ? thinks its bad.

DPE shot ? no good

Main Winding ? what you think .

 

A few things that you have said concern me greatly - starting with the genset always being under substantial load.


This set is rated for 66.6A @ 120V, or 33.3A @ 240V.

Exactly how large of a load are you pulling?

What type of load?

 

It really sounds like you have over heated the genset and burnt it up.

 

The DPE winding showing open means the stator is bad.

The high resistance of the rotor means either the rotor is bad, or the slip rings are very dirty.

 

The 0.6 ohms on the power windings may still be OK - but it does not matter. If the DPE is bad, the stator must be replaced anyhow.

 

I would suggest really checking the slip rings and rotor.

This stator will run you between $500 and $600, and the rotor will run you about $300.

 

If you need them, here are the part numbers:

stator - 204285GS

rotor - 205174GS

 

Customer: replied 6 years ago.

THis is a construction site generator that a carpenter contractor owns so loads such as air compressors and saws possibly lighting as well.

 

I made a mistake on the reading of the rotor. My mistake. The rotor = 8.5 ohms

 

The rotor is good then right ?

I havent done any other checks to the rotor yet. Their is a diode in their hu?

its been worked but i would think it is still good. Agian the rotor is with in 7.7 - 9.5 ohms which you gave me those values

 

i will accept your awnsers after this one. i am honest.

i do appreciate your help i plan on ordering the stator from "jackssmallengins" .com

Yes, this would indicate that the rotor is OK.

 

There is not diode in the rotor - there is only the 2 slip rings and the winding - this is why it is so important to ensure the brush leads are connected properly.

 

Jacks is a very good place to buy parts - they are very often the cheapest I can find.

 

Good luck with the genset.

 

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