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14V alternator harness..

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Talns100

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Hello, in the diagram shown below we can see a harness is connecting between the 14V stator and the regulator. It is also showing that the current is AC.
If this is the case and the regulator gets 14V AC why is there a rectifier connected to the stator?
The manual also says that the current is rectified so I don’t really get what is happening.
N1505 alternator + N3135 regulator

IMG_1469.png
 
Mogman

Mogman

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That drawing is more representative than actual as the upper stator is not shown complete as there must be more rectifiers on the upper stator to produce DC, I assume the phased harness is used so the 14V source can be rectified and regulated independently from the 28V output.
It takes 6 diodes to form a 3 phase rectifier.
 
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Talns100

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Mogman said:
That drawing is more representative than actual as the upper stator is not shown complete as there must be more rectifiers on the upper stator to produce DC, I assume the phased harness is used so the 14V source can be rectified and regulated independently from the 28V output.
It takes 6 diodes to form a 3 phase rectifier.
Click to expand...
It seems the 14v source is rectified at the regulator and not in the alternator as they say in their manual.
What is actually going on?
 
Mogman

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This is what is "going on with the 28V stator, the diode drawn between the +28 output terminal and ground represents the 6 diode rectifier, if you use an ohm meter connected to the +28 output terminal and ground (the case) you will see conduction in one direction only just like the single diode drawn in the docs.
On the 14V side they are likely using SCRs in the rectifier instead of plain diodes to independently regulate the 14V tap, let me see if I can find a schematic of how that would look.
Here is an example of what is going on in the 28V circuit with the 6 diode rectifier being represented by the single diode.
alt.JPG
The field in these alternators do not have slip rings and brushes as shown in this schematic.
 
Mogman

Mogman

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This is probably close to what is going on with the 14V side of the alt
On the 28V side the reg controls the field winding to control the 28V output on the 14V side it uses SCRs (or something similar) to regulate the 14V output independent of the 28V output.
The phase cable takes the three phase stator output to the regulator where it rectifies it and controls the voltage inside the regulator itself.
It does this by basically turning on and off the SCRs to control the 14V output.
This type of scheme is by far the most efficient way to regulate a three phase output, much more efficient than using a linear regulator after rectification.
An SCR is basically a diode that you can control using its third lead and are the three rectifiers in the bottom of the schematic.
SRC.JPG
 
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Talns100

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Mogman said:
This is probably close to what is going on with the 14V side of the alt
On the 28V side the reg controls the field winding to control the 28V output on the 14V side it uses SCRs (or something similar) to regulate the 14V output independent of the 28V output.
The phase cable takes the three phase stator output to the regulator where it rectifies it and controls the voltage inside the regulator itself.
It does this by basically turning on and off the SCRs to control the 14V output.
This type of scheme is by far the most efficient way to regulate a three phase output, much more efficient than using a linear regulator after rectification.
An SCR is basically a diode that you can control using its third lead and are the three rectifiers in the bottom of the schematic.
View attachment 938936
Click to expand...
If the 14V is rectified at the regulator why do they say it is internally rectified ?
 
Mogman

Mogman

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After reading the guide again they are employing a type of rectification on the 14V stator, this would be half wave rectification which can be regulated in the same manor as AC in the 14V example above using SCRs , so technically they are rectifying "internally".
I apologize for my error.
 
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Talns100

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Mogman said:
After reading the guide again they are employing a type of rectification on the 14V stator, this would be half wave rectification which can be regulated in the same manor as AC in the 14V example above using SCRs , so technically they are rectifying "internally".
I apologize for my error.
Click to expand...
It’s ok I think the diagram is very misleading
I still don’t get it :(
 
Mogman

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In the alternator it would look like this, it would require a WYE three phase stator, not the DELTA stator shown.
I have never seen a WYE stator used in automotive applications because the DELTA configuration is much more efficient but I suppose they were not too concerned about the efficiency of the 14V circuit.

They give enough information for troubleshooting, it is not a full engineering document.

But yes, showing a DELTA three phase 14V stator and AC going to the alt on the phase cable (this BTW is completely separate from the "phase signal" referred to on page 4) it is technically incorrect, the phase cable carries half wave (pulsing) DC

Troubleshooting guides are written by technical writers not engineers and I have found many errors over the years some of which are significant.
If it was written by an engineer it would be at least 250 pages :)
Half wave.JPG
 
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Talns100

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Mogman said:
In the alternator it would look like this, it would require a WYE three phase stator, not the DELTA stator shown.
I have never seen a WYE stator used in automotive applications because the DELTA configuration is much more efficient but I suppose they were not too concerned about the efficiency of the 14V circuit.

They give enough information for troubleshooting, it is not a full engineering document.

But yes, showing a DELTA three phase 14V stator and AC going to the alt on the phase cable (this BTW is completely separate from the "phase signal" referred to on page 4) it is technically incorrect, the phase cable carries half wave (pulsing) DC

Troubleshooting guides are written by technical writers not engineers and I have found many errors over the years some of which are significant.
If it was written by an engineer it would be at least 250 pages :)
View attachment 938961
Click to expand...
Alright so if the phase carries half wave pulsing it means that it’s not rectified in the regulator they just use 3 phase connection
 
Mogman

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Talns100 said:
Alright so if the phase carries half wave pulsing it means that it’s not rectified in the regulator they just use 3 phase connection
Click to expand...
Yes but the regulator circuit would still look much like the 14V example above.
That three phase half wave signal is not very useful as it is, it still must be regulated, combined and filtered.
 
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Coug

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Regulator takes AC input and uses it for both rectifying to the 14V tap output, and likely for monitoring output to regulate both the 14V and 28V output of the alternator.
Remember, this is 30-40 year old technology that they are still using, so it tends to be a bit more complicated than modern solutions.
 
Retiredwarhorses

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Coug said:
Regulator takes AC input and uses it for both rectifying to the 14V tap output, and likely for monitoring output to regulate both the 14V and 28V output of the alternator.
Remember, this is 30-40 year old technology that they are still using, so it tends to be a bit more complicated than modern solutions.
Click to expand...
im still trying to figure out in the absence of an Inverter, that you can have AC…the regulator is not an inverter
 
Mogman

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Retiredwarhorses said:
im still trying to figure out in the absence of an Inverter, that you can have AC…the regulator is not an inverter
Click to expand...
An automotive alternator makes AC, (three phase AC actually) that is why it is called an alternator and not a generator, it then needs to be rectified into DC this can be done inside (most modern alternators) or outside of the alternator.
 
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