Jordan wrote:ducwiz wrote:
But in a 2phase system we measure the same AC voltage between each phase/branch and the neutral/center wire, but twice that voltage between the two phases!
The second difference:
The phase angle in a 3phase system is always 120° between two branch/phase voltages, but 180° between the two phases/branchs of the 2phase system.
Hans
I have trouble with this definition of two phase.
Assuming centre tap is not connected and diodes not included, if the phases are 180 degrees apart, would not the AC voltages in the two branches cancel each other, resulting in zero volts output?
I might be wrong, but think that they are in phase, so that is why they can provide increase voltage when used together?
However, half wave rectified
DC voltages could be 180 degrees apart.
This is the situation in a
single phase, centre tapped, full-wave type alternator.
Jordan,
here comes a little "enlightment"
:
Basically, if you do not connect the center tap anywhere, the alternator consists of two identical windings, connected in series. This means, their voltages sum up, not cancel themselves out. This would happen in case of paralleling them (see my last post).
Experiment: ground red/center tap and the observe the phase angle of the voltages on a 2channel osciloscope. You will realize 180° phase difference.
Btw., even the older n/c 60W alternator is also a 2phase version, but here the center tap is locally grounded and the stator plate. This results in only 2 wires coming out from the motor. The reference/neutral/center tap or however else one likes to name it is the chassis of the bike itself!
So, for me, a
single phase, centre tapped, full-wave type alternator as you name it, does not exist. A single phase alternator always has only two terminals/wires only, no tap. It can be floating from ground an rectified by a bridge, or grounded on one side, so only a half-wave rectifier is possible.
Again: The expression "2phase" is only justified if a reference (i.e. center tap) terminal/connection is present, against which the two "phases" have a non-zero phase angle.
Btw, the 12Volt conversion of w/c alternators is based on omitting/disconnecting the red wire/center tap and feeding a bridge rectifier from the two yellow wires. The result is a doubled AC input voltage, and in turn a 12V DC system. OK, a new R-R for 12V is needed. Today, people use cheap chinese scooter regulators based on the shunt regulation principle. This was discussed and shown in earlier threads. Many years ago, I converted the original Ducati R-R (series regulation) by adding 2 power diodes to form a bridge, and a small electronic circuit connected between the "marrone" terminal and battery+. This little device subtracts 7 Volt from the battery voltage. My conversion thread can also be found somewhere.
cheers Hans