Portable Honda Petrol Generator Not Producing Enough Voltage

Harry Palmer · Sunday at 5:02 PM

Hi,

Trying to get to bottom of my portable petrol generator voltage issues, engine is a Honda GX160 with a non-branded generator 240/110v outlet bolted on to it, recently started her up with a very weak current, multimeter showed only half the voltage being generated e.g 240v outlet, actual =120v and the 110 v outlet actual = 50v

I don't presume to know much about portable domestic/light commercial petrol generators hence my polite request for guidance/help. I have attached several pictures of both the actual Stator assembly and Rotor etc for illustration purposes only
hoping some kind knowledgeable soul will point me in the right direction. The Honda petrol engine works fine and when I plug a 240v drill in the outlet socket I can hear the engine rev up under load but the voltage is not enough to power the drill, also tried other 240v power tools and a hair dryer and same result, I am familiar working with a multimeter but I don't know how to test if the Rotor and or Stator assembly windings have had it, the generator is a brush-less type, I see no scorch marks on both windings and have replaced the 16uf capacitor for new with no difference, any help in diagnosing to determine the cause of the low voltage would be greatly appreciated Ps. placed to multimeter to test for current on the two black wires (just slightly out of shot) witch attach to the capacitor and I am getting 14v AC reading, if that is of ant help - Thanks in advance

Rockingit · Sunday at 5:57 PM

If the engine is spinning at speed (1500rpm final spindle speed) then sorry to say more than likely you have a burnt out winding

Harry Palmer · Sunday at 7:00 PM

Rockingit said:
If the engine is spinning at speed (1500rpm final spindle speed) then sorry to say more than likely you have a burnt out winding

How do I check the RPM please?

UNG · Sunday at 9:09 PM

Harry Palmer said:
How do I check the RPM please?

Google hand held tachometer gauge

Harry Palmer · Sunday at 9:54 PM

UNG said:
Google hand held tachometer gauge

Thanks, but what I would really like to know if possible is how I test the windings on both Rotor and Stator assembly for the correct resistance and what the readings should be on the two parts if good?

Avo Mk8 · Monday at 11:03 AM

The T25-4 diodes seem to be forming a bridge rectifier arrangement connected to the rotor windings.

I'm not up on generators, but I gather there can be an issue when after a long period of no use, residual magnetism in the rotor that is needed to get generation going, drops to such a low level it doesn't start properly.
There's apparently a technique of "flashing" the armature with a car battery to give it magnetism. I know nothing about this other than if not careful you can kill the whole thing for good !

There must be some on here familiar with these things!

I can't answer your queries about winding resistances I'm afraid.

As a matter of interest, are there slip-rings or a commutator on the far end of the armature that's not in the photo's - or nothing? (Having done a little more research, I think it's probably 'nothing')

Finally - irrespective of the connectors on it, are you sure it's actually a 240V generator (I imagine it is), and not a 110V one? Does it have a rating plate with details?

Edit: with a bit of scrap magnetic material (but not itself a magnet!) you could check to see if the rotor has reasonably strong residual magnetism, or none!?

James · Tuesday at 8:47 PM

I am not 100% up on generators but here goes my theory's.

The rotor is there to generate a magnetic field, it has 2 interconnected sides to create a N-S field
This is done using DC voltage to create a constant field that is then rotated at speed past the stator windings.
this in turn produces your AC voltage in the stator windings.

The voltage produced is down to the number of turns in the stator windings and the strength of the magnetic field passing through them.
the frequency produced is down to the rotational speed of the field passing the stator windings.

so further to that, if the rotor windings had a fault that meant only one side was being energised then the voltage would be roughly half of what you expect.
this is because a stator winding is split in 2, half on one side and half on the opposite side at 180 degrees opposed.
therefore only half of the stator winding is being excited as the field is only passing by on one side.

I would be looking at the diodes to ensure they are working correctly, there may also be an AVR involved.
Automatic Voltage Regulator's regulate the voltage applied to the rotor thus changing the field intensity and regulating the output voltage.

Harry Palmer · Tuesday at 9:34 PM

James said:
I am not 100% up on generators but here goes my theory's.

The rotor is there to generate a magnetic field, it has 2 interconnected sides to create a N-S field
This is done using DC voltage to create a constant field that is then rotated at speed past the stator windings.
this in turn produces your AC voltage in the stator windings.

The voltage produced is down to the number of turns in the stator windings and the strength of the magnetic field passing through them.
the frequency produced is down to the rotational speed of the field passing the stator windings.

so further to that, if the rotor windings had a fault that meant only one side was being energised then the voltage would be roughly half of what you expect.
this is because a stator winding is split in 2, half on one side and half on the opposite side at 180 degrees opposed.
therefore only half of the stator winding is being excited as the field is only passing by on one side.

I would be looking at the diodes to ensure they are working correctly, there may also be an AVR involved.
Automatic Voltage Regulator's regulate the voltage applied to the rotor thus changing the field intensity and regulating the output voltage.

I have uploaded a specific picture of the Stator and commented in response to your kind thoughts, I have carried out a resistance check and buzzer test on what I believe are the Diodes on the Stator, 0 resistance [O/L] and NO buzzer by placing test probes one at each Diode not to be confused with testing each individual Diode (bridged), but I am not sure this is a reliable test to ensure the Stator is in good working order in terms of the Stator windings!

If they are indeed Diodes on the Stator they I am at a loss in terms of how to test if they are good or bad, You mention AVR as I have no wiring schematics for this generator I can only assume that it does not have a AVR, however could it be attached to the Honda engine rather then the generator, as I have not looked at the engine side?

Harry Palmer · Tuesday at 9:45 PM

Avo Mk8 said:
The T25-4 diodes seem to be forming a bridge rectifier arrangement connected to the rotor windings.

I'm not up on generators, but I gather there can be an issue when after a long period of no use, residual magnetism in the rotor that is needed to get generation going, drops to such a low level it doesn't start properly.
There's apparently a technique of "flashing" the armature with a car battery to give it magnetism. I know nothing about this other than if not careful you can kill the whole thing for good !

There must be some on here familiar with these things!

I can't answer your queries about winding resistances I'm afraid.

As a matter of interest, are there slip-rings or a commutator on the far end of the armature that's not in the photo's - or nothing? (Having done a little more research, I think it's probably 'nothing')

Finally - irrespective of the connectors on it, are you sure it's actually a 240V generator (I imagine it is), and not a 110V one? Does it have a rating plate with details?

Edit: with a bit of scrap magnetic material (but not itself a magnet!) you could check to see if the rotor has reasonably strong residual magnetism, or none!?

Not sure what you mean when you say 'are there slip-rings or a commutator', please excuse my ignorance.

To answer your other questions, unfortunately it does not have a data plate, it is both a 240v and 110v generator as I have 110v power tools when working on site that has no power, all has been working fine however The generator has been left idling in my garage for a long time, now I have need of it, it certainly is not behaving its self. Will test your theory of magnetism with iron filings. Will try and keep all that have taken the time and effort to help with any developments - Thanks

James · Tuesday at 9:56 PM

If I were to take my best guess, it would be a diode that has failed

Harry Palmer · Tuesday at 11:35 PM

James said:
If I were to take my best guess, it would be a diode that has failed

Sounds plausible, but can this part be tested with a multimeter ? I remember that they are one direction in terms of current passing through them so you have to decide which way in travels in order to obtain a reading, any thoughts?

plausible

Harry Palmer · Tuesday at 11:38 PM

Avo Mk8 said:
The T25-4 diodes seem to be forming a bridge rectifier arrangement connected to the rotor windings.

I'm not up on generators, but I gather there can be an issue when after a long period of no use, residual magnetism in the rotor that is needed to get generation going, drops to such a low level it doesn't start properly.
There's apparently a technique of "flashing" the armature with a car battery to give it magnetism. I know nothing about this other than if not careful you can kill the whole thing for good !

There must be some on here familiar with these things!

I can't answer your queries about winding resistances I'm afraid.

As a matter of interest, are there slip-rings or a commutator on the far end of the armature that's not in the photo's - or nothing? (Having done a little more research, I think it's probably 'nothing')

Finally - irrespective of the connectors on it, are you sure it's actually a 240V generator (I imagine it is), and not a 110V one? Does it have a rating plate with details?

Edit: with a bit of scrap magnetic material (but not itself a magnet!) you could check to see if the rotor has reasonably strong residual magnetism, or none!?

I have of the term '"flashing" will look in to this further - Thanks

Avo Mk8 · Tuesday at 11:51 PM

Harry Palmer said:
Sounds plausible, but can this part be tested with a multimeter ? I remember that they are one direction in terms of current passing through them so you have to decide which way in travels in order to obtain a reading, any thoughts?

Just to say that each diode is the shape below (example only, not the exact ones)
So you need to test each between the wire end and the metal body in the middle.
If Disconnected the diode would conduct (a low resistance) with multimeter probes round one way, and not conduct (high resistance) with probes reversed.
I'm not sure if you will be able to tell the difference with coils connected as I'm mot sure how they are wired!!

Avo Mk8 · Wednesday at 5:59 PM

Harry Palmer said:
I have of the term '"flashing" will look in to this further - Thanks

Page 6 of this might be of interest. Don't know if it can be used for your specific model?

https://www.absolutegenerators.com/media/blfa_files/Gillette_Portable_Generator_Service_Manual.pdf?

PS Electrics · Wednesday at 8:54 PM

Avo Mk8 said:
I'm not up on generators, but I gather there can be an issue when after a long period of no use, residual magnetism in the rotor that is needed to get generation going, drops to such a low level it doesn't start properly.
There's apparently a technique of "flashing" the armature with a car battery to give it magnetism. I know nothing about this other than if not careful you can kill the whole thing for good !

I think you are correct