Checking Generator Windings.

[Dave100456]

Hi
Can someone please advise how to check the windings resistance on my genny. The manual says check Stator, Rotor and Excitation but is this to earth or across the wires? I have the following 7 wires coming out which I can't identify.

1st green and 2nd green going to a large capacitor.

Blue to earth and Blue to what looks like a voltage regulator finned alloy component.

1st Red and 2nd Red (are these the phases?) going to N and L output.

Yellow not connected to anything.

Thanks
Currently sailing so I may not be able to get back to you soon.

 

[VicS]

Make and model ?

got a link to to the manual ?

Is there a diagram that ids these wires? ........ can you scan or photo it and post it?

Basically though I expect it is asking you to measure the resistance between the two reds , between the two greens and between the two blues. I'd expect a diagram in the manual to id which pair is which.

 

[Dave100456]

Thanks Vic
What you say makes sense and I'll see what readings I get.
The genset is a Paguro and the manual's not vey detailed.

 

[superheat6k]

The Paguro with the Farymann engine appears in many guises (Mastervolt, Fischer Panda, HFL, Westerbeke, etc), and I have quite a few manuals for various makes, but for some reason the generator windings seem to be an Italian state secret as none show the details of the AC voltage side.

I do have a Kohler manual with very detailed diagrams, but this is definitely not the same unit as the Paguro. The winding layout may be similar - if you want a copy PM me and I can send you a link.

 

[William_H]

Can only talk in geral terms about a 240vAC alternator. (all right generator to you). Usually the rotating coil will be the field coil with connections coming out to slip rings. Probaly runs on about 150v DC but variable with regulation. Thsi DC comes from rectifying and regulating a sample of the AC out.
The power comes from the stator windings . One winding for single pahse 3 windings all connected together for 3 phase out put. The single phase stator might have a resistance or 2 or 3 ohms or something of that order. One woulde xpect a connection directly from the stator tot he outlet socket but would also have a sampling take off to the regulator and field coild driver circuits.
A simple test is to run the generator and just see if there is any voltage (No load) AC at the outlet socket or connection. If you get some volts 20 or 30 then it would indiccate the alternator is not getting excitation voltage.This small voltage comes from residual magnetism. Check to see if there is any voltage DC at the brushes of the slip rings. If you have a voltage (4 to 10 volts) at the brushes this might mean either poor contact with the slip rings so voltage is not getting to the field coil or the coil is open circuit.
More likely however is if you have a small output voltage but nothing to the field coils that the regulator circuit is kaput. Check the physical condition of the components as vibration can be the biggest killer on small generators and electronics. Old generators might have a electromagnet and contacts where high output voltage operates the coil against an adjustable spring to set voltage. More modern gens will have a transsitor contolling the current as decided by a comparator to a voltage referrence. Sommewhere might be a voltage set control. This info might help a bit. good luck olewill

 

[Dave100456]

William
Thanks for the info, will prove useful.
Dave

 

[superheat6k]

I have found this diagram, which is likely to be the layout of your generator, but it is a bit sparse.

For the output you may have two pairs so these would be series connected for 240v and paralleled for 110v

http://4.bp.blogspot.com/-0IqoNQfrHrg/U2HTNd6HWiI/AAAAAAAAr6g/5bs70tzXpqM/s1600/regulssator.png

 

[bristoljim]

Do not forget that the neutral side of the output will be tied down to earth to make your protection work , not shown on Superheat6k's drawing.

Good luck Jim

 

[William_H]

I have found this diagram, which is likely to be the layout of your generator, but it is a bit sparse.

For the output you may have two pairs so these would be series connected for 240v and paralleled for 110v

http://4.bp.blogspot.com/-0IqoNQfrHrg/U2HTNd6HWiI/AAAAAAAAr6g/5bs70tzXpqM/s1600/regulssator.png

Interesting actual diagram of what I was trying to describe. The difference seems to be that they have a separate winding (labelled field winding) which is not actually a field winding but rather a special winding to supply the field current. It is rectified in the bridge diode (diamond shaped 4 diodes) The current is controlled by the transistor (circle 3 connection device) . The transistor is then controlled by the voltage detection box (more electronics not described) which samples the output 240vAC voltage.
So if you load up the AC output the output voltage falls which is detected and results in more current to the base of the transistor which then allows more current to go to the field coil via the slip rings.
I imagine they have a separate field supply pick up winding to give a low voltage like 12v to 25v more suitable for control by an old style transistor and suitable for a low resistance (rotating) field coil.

good luck olewill

 

[Lon nan Gruagach]

Interesting actual diagram of what I was trying to describe. The difference seems to be that they have a separate winding (labelled field winding) which is not actually a field winding but rather a special winding to supply the field current. It is rectified in the bridge diode (diamond shaped 4 diodes) The current is controlled by the transistor (circle 3 connection device) . The transistor is then controlled by the voltage detection box (more electronics not described) which samples the output 240vAC voltage.
So if you load up the AC output the output voltage falls which is detected and results in more current to the base of the transistor which then allows more current to go to the field coil via the slip rings.
I imagine they have a separate field supply pick up winding to give a low voltage like 12v to 25v more suitable for control by an old style transistor and suitable for a low resistance (rotating) field coil.

good luck olewill

Look again, its a poorly drawn diagram. There are thin lines from the labels "field" to the rotor coil and "excitation" to the extra stator coil, just as you would describe for this set up.

 

[VicS]

Interesting actual diagram of what I was trying to describe. The difference seems to be that they have a separate winding (labelled field winding) which is not actually a field winding but rather a special winding to supply the field current. It is rectified in the bridge diode (diamond shaped 4 diodes) The current is controlled by the transistor (circle 3 connection device) . The transistor is then controlled by the voltage detection box (more electronics not described) which samples the output 240vAC voltage.
So if you load up the AC output the output voltage falls which is detected and results in more current to the base of the transistor which then allows more current to go to the field coil via the slip rings.
I imagine they have a separate field supply pick up winding to give a low voltage like 12v to 25v more suitable for control by an old style transistor and suitable for a low resistance (rotating) field coil.

good luck olewill

Look again, its a poorly drawn diagram. There are thin lines from the labels "field" to the rotor coil and "excitation" to the extra stator coil, just as you would describe for this set up.

Surely the field current is generated by the coil labeled "excitation" and rectified by rectifier RB.

The rectified current is then controlled by the transistor, Q, and the "voltage detection circuit" and fed via the brushes and slip rings to the field coil on the rotor.

but there seems to be a connection between the voltage detector and the transistor emitter missing


(I would think that the brushes and slip rings have been drawn incorrectly.. I'd expect the field coil to be connected to the slip rings and the controlled field current to be fed to the brushes)

 

[superheat6k]

I did mention it was a bit sparse, but this all I could find for the VTE (Volpi) generator these small generator sets mostly use.

Loads of 12v wiring diagrams for the various generics, but virtually nothing for the alternator end of the genny. I do have detailed wiring diagrams for a larger Kohler set, but this bears no relation whatsoever to the smaller Farymann driven units. The electrics on these units are fairly simple, just a capacitor and some diodes, but fathoming out the coil windings without resorting to a rewind shop is seemingly impossible.

Without knowing this providing sound advice on where to fault find becomes very difficult.

 

[William_H]

Surely the field current is generated by the coil labeled "excitation" and rectified by rectifier RB.

The rectified current is then controlled by the transistor, Q, and the "voltage detection circuit" and fed via the brushes and slip rings to the field coil on the rotor.

but there seems to be a connection between the voltage detector and the transistor emitter missing


(I would think that the brushes and slip rings have been drawn incorrectly.. I'd expect the field coil to be connected to the slip rings and the controlled field current to be fed to the brushes)

hello Vic. Yes you are right in that the Voltage Detction Circuit should have a connection to the emitter (or earth) to control the current through the transistor. I presume omitted for simplicity of the diagram.
I did not notice the little lead lines to the coils in first post. The location of the name is misleading but the lead lines clarify.
Perhaps you have laso been misled by location of labels. The field coil is of course the rotating coil and is connected to the slip rings.
Just to waffle on there is another arrangement on more sophisticated generators (alternators) called brushless design. The pick up stator coils are the same as are the rotating field coils. However the field coils on the rotor have an additional coil on the end which is actually another generator. Diodes on the rotor connect the main field coil to the additional rotating coil. Stator coils around the additional part carry DC as controlled by a regulator. So this Dc gives a magnetic field from the outside of this additional generator on the end of the shaft. The rotating coil picks up AC which is rectified and fed to the main field coil. All within the rotating part. So no brushes and a very reliable generator as used on jet aircraft.
Incidentally the mechanical drive is very sophisticated to give a constant generator speed hence constant frequency (400hertz) from a variable speed engine. (jet engines varying only by a factor of 2 to 1 from idle to max). good luck olewill