Yet another rectifier thread...

Originally Posted by Baph

EDIT: just a thought, but the dual pole output could be a weak attempt at dual phase rectifying via an operational amplifier, but I'll look more into that when it's not so late

Ah ha!

Originally Posted by google-fu magical website

As the magnets pass by the alternator coils the output voltage slowly build to a positive peak, then decays passing through zero, slowly builds to a negative peak, then decays passing through zero. This is a sinusoidal wave shape, similar to ripples on a pond. Since the system needs Direct Current (DC) in order to charge the battery, the device Lucas chose to convert between the two is called the rectifier. Several styles can and have been used over the years. The first style is the selenium stack full wave bridge rectifier. It consists of four selenium solid
state diodes connected as a electronic bridge and mounted to individual flat plates and stacked vertically. Terminals jut out from the stack such that two are used for AC input and two are used for DC output. One of the output terminals may be the mounting stud on the base of the stack. A more modern rectifier bridge uses the four terminals, but is an encapsulated module made up internally of silicon diodes that are much more robust electrically. The rectifier works to isolate the alternator findings from the battery to minimize the alternator's ability to discharge the battery when the engine is not running, and in converting AC to DC. In converting from AC to DC it flips the negative part of the sinusoidal alternator output to be positive. This makes for only positive going lumps or ripples of voltage. On the average it is DC but instantaneously it still goes from zero to maximum positive voltage and back to zero again. But, the peak voltage level of the voltage changes based on the engine RPM, hardly what anyone would term regulated.

Techno-babble for "Baph was right, they use dual pole outputs for rectifying." However, they're not using dual phase via the op amp like I thought. Much more efficient to use diodes & wire them up accordingly, so you get a full wave rectification with half the components, on double the outputs Why didn't I think of that before? *smacks head*

So that explains (to me at least) why pointy reg/rects have 2 black&red, and 2 black&white wires

Confused?

Not arf'.

It's late.

Because the rectifier uses full wave rectification, but half components on double the outputs, you'd probably get a true (steady) DC level of about 75% of peak too, which would explain why some people have said that whilst revving, the battery should show around 14v. (18v output at peak, 75% is 13.5v - but those are picked from my very dubious memory). But that's getting off topic a little

If all of the above does turn out to be true, it would mean that pointy/curvy rectifiers were completely electronically interchangeable (though maybe not physically). Also, by design (less components == less heat) a pointy rectifier would be less susceptible to failure than a curvy one, but this doesn't take into account manufacturing perspective. Just a thought

Anyhow, time to get some ZZZ's. Let me know how you get on

[Sid Squid]

Originally Posted by Baph

EDIT: just a thought, but the dual pole output could be a weak attempt at dual phase rectifying via an operational amplifier, but I'll look more into that when it's not so late

Stop thinking so hard.

It's exactly the same as the earlier regs, three alternator wires, a hot and a neg, (on this exact unit of which there are two of each).

Originally Posted by Sid Squid

Stop thinking so hard.

It's exactly the same as the earlier regs, three alternator wires, a hot and a neg, (on this exact unit of which there are two of each).

Hey, it was late & I was trying to fathom why there would be 2 +ve & 2 -ve wires. Give me a break :P

Haven't quite got it wired up yet due to not being able to get some decent wiring stuff today but will do that tomorrow. Had a look at the rectifier itself and noticed on the back there was a crack and looked like it had burnt out. I guess that is a way of telling if it's buggered?