[url=https://classicgoldwings.com/forum/viewtopic.php?p=219760#p219760:32tl4f1z said:
Ansimp » Today, 12:17 am[/url]":32tl4f1z]
The Mofset regulators that we have been using as described by Aussiegold do exactly as you described they use high frequency switching to provide regulated output at a consistent voltage
It has been some time since I read about it, but recalling what I read, I'm fairly certain those regulators still use shunt regulation. What I described, is referred to as PASS regulation, rather than SHUNT regulation.
High frequency switching is not the key factor, as EVERY shunting operation of the output WILL be high frequency. MOSFET isn't the key factor, either... a MOSFET is nothing more than a transistor, it just happens to be a very robust type well-suited to switching considerable amounts of power.
The process of generation that the permanent magnet field regulator employs, is a 'full trough' approach... and here's a mechanical explanation:
You have a windmill, on a hill. As the wind blows, the windmill spins, and pumps water up from the aquifer, into a watering trough.
Cattle drink from the trough.
Problem- the wind blows... sometimes slow, sometimes fast. The cattle only drink so much. When it's hot, the cattle drink more, when it's cold, they drink less. When the wind blows, it's usually cold, and when the wind is slow, it's usually hot, so the amount the cattle drink is frequently OPPOSITE in proportion to when wind will pump it.
Fortunately, the trough only holds a fair amount of water... but it's not infinite.
When the wind blows fast, the trough fills rapidly, but overflows rapidly.
The shunt regulator is nothing more than an overflowing trough. The windmill is spinning, pumping water like crazy, which flows into the trough, then overflows onto the ground, which not only makes a muddy mess, it rapidly depletes the shallow aquifer of the river valley below.
So the rancher installs a valve in the well pump's supply... and a float on it's control lever. When the trough water level rises, it shuts off the flow from pump to trough. This causes pressure in the pump supply line, and eventually, stalls the windmill... which is a great idea, except for the fact that it's a really big windmill, and when the trough is full, it's because it's cold, windy, and the cattle aren't drinking.
If we were to do the same thing with the permanent magnet alternator, it would be referred to as "PASS" regulation. In pass regulation, there is no 'dump' to return, hence, it doesn't allow the source to expound energy moving something that will be discharged as waste.
Like the stalled windmill, going to 'pass' regulation on a permanent magnet alternator is 'not' without inherent risk. When wind blows on a large, stalled windmill, there's a high likelyhood that something will break... like the gearbox, or the sucker-rod, or the furling gear, or even rip the flights off the wheel. In the permanent magnet alternator, the magnet is still spinning, and the stator is still in that whirling magnetic field, so it is STILL trying to generate. While it flows no current, there is still voltage appointed upon the coils, which is no longer 'clipped off' by a shunt regulator dumping hordes of current to ground... which means the coils' voltages are skyrocketing. The diode bridge is thus being hammered by much higher voltages AND... the stator coils' windings are seeing substantial voltages within the windings, because a coil under induction, with no load, develops squirrly eddy currents. With the insulation being somewhat of a long distributed capacitor, it isn't long before insulation resistance becomes insufficient to cope, and then it burns through and becomes a short circuit.
The benefit of shunt-regulating the PMA is simplicity and durability. The detraction is that it imposes a base parasitic load on the engine wether it's output is used, or not.
The benefit of a pass regulation scheme, is that the base parasitic load is mostly eliminated. The detraction is that it's subject to a bit more complexity (much less now, than two decades ago), and that the stator and rectifier bridge must be capable of withstanding some very high voltages.
The PMA scheme that shows up in our motorcycles had an interesting start. The concept of 'shunt regulation' is the opposite of the mechanical field regulator (aka 'cutout') found on early motorcars and farm tractors. During WW2, Karl Kiekhaefer utilized a mechanical field cutout to 'shunt regulate' a crude PMA on motors he'd built for flying target drones. He later used this same concept through outboard motor development, and this is why you'll see a disproportionate amount of early Mercury outboard motors having electric start... and others (like Evinrude and Johnson) having electric start, but NO battery charging ability... Carl held the patent.
Aside note... as part of shunt-winding excess, PMAs generate lots of waste heat... and because of how they're made, they don't get much cooling airflow. It's a wonder that they don't overheat, but Carl was one really sharp dude... he made the top end of his outboard motor crankcase with an enlarged water jacket RIGHT UNDER that PMA stator ring. Now take a close look at your motorcycle's PMA stator, and tell me... what did THOSE engineers do, to keep it cool? There's two ways: 1) Follow Carl's lead and find a way to get more cooling flow there... or 2) reduce the stator's output capacity, so it can't get so hot... (is THAT why the battery on my Kawasaki was always dead?? :doh: )
The 'best' way to get both worlds, is to NOT use a permanent magnet field... instead, use a PASS regulated WOUND field... but this means slip rings and brushes, which is what a modern alternator uses.
And that's why lots of Goldwing guys just nix the melted system and fit a small car alternator to the front of the engine. Matter of fact, it was such a good idea... HONDA did it too!!! :smilie_happy:
oh2:
