Tracker generators come in 60-amp, 70-amp and 80-amp sizes. Technically they are alternators but Suzuki and Chevy use the term generator so I will too.

The parts of the generator that produce current are the rotor (the rotating part) and the stator (the stationary part).


In a bicycle dynamo the rubber tire spins a shaft. There are a series
of permanent magnets attached to the rotating shaft. The magnets
reside inside a stationary coil of wire. When the rotor shaft spins,
the magnets spin and the magnetic field around each magnet also
spins. This rotating magnetic field is the essence of a generator.
Because the magnetic field extends a short distance outside the
magnet, it cuts through the wires of the stationary coil surrounding
it when it spins. That cutting action induces a current into the stator
winding. The problem with this setup is that the amount of current
produced is determined solely by the speed of the bicycle. This is
not a practical generator for a car. What's needed is a rotor
with a magnetic field that can be increased or decreased on demand.
Fortunately that can be done by replacing the permanent magnet
with an electro magnet.


Here the rotor magnets have been replaced by a coil of wire. When the transistor switch closes,
battery current flows through the rotor coil. That current converts the rotor coil into an electro
magnet. When the rotor spins, the magnetic field of electro magnet cuts through the stationary
windings and produces current just like the bicycle dynamo. The difference here is if the induced
current produces a voltage too large for the battery to handle, the transistor switch can shut off
the rotor current, turning the rotor magnet off. Without a magnetic field the spinning rotor can't
produce current in the stator.


Tracker generators have three stator windings. That means it can produce three currents at once. The stator windings
are positioned 120° apart so the three currents start at three different times. Each horizontal division in the chart above
represents 90°. The blue current starts at the left edge of the chart at 0 volts and goes positive. 120° later the green
current crosses zero volts and goes positive. At 240° the red current crosses zero and goes positive. At 360° the rotor
has made one full revolution and the process starts over. It may not be clear from looking at the chart but every time
the current is below the zero-volt line, it is traveling it the opposite direction. Alternators produce alternating current (AC).
The next step is to convert this alternating current to direct current (DC) because everything in the Tracker's electrical
system runs on 12 volts DC.

 

To simplify things I'm going use the battery as a representation of the entire electrical system.
For this sexample, charging the battery is assumed to be sole purpose of the generator.
Lets see how that happens. The six diodes inside the generator form a rectifier circuit.
The purpose of the rectifier is to redirect the negative currents from the stator windings
into positive currents. For this discussion current is "conventional" current (not electron flow).
During discharge, conventional current flows from positive side of the battery, through
the circuit, and back to the negative side of the battery. When the battery is charging,
conventional current flows into the positive battery anode and out the negative anode.
To make this happen the output from the rectifier must remain positive and slightly higher
than 12 volts. Here's how that happens.


This diagram shows the operation of the diodes through a full 360° rotation of the rotor. It is very complex but all you need to know is, (A) only two diodes are working
(forward biased) at any one time and (B) current only travels in the direction of the arrow on the diode symbol. Just remember the top of the rectifier is connected to
the positive side of the battery and the bottom of the rectifier is tied to the negative battery terminal.


Assume you had a magic voltmeter with the red lead on the blue winding and the black lead on the green winding. The magic meter leads always have to be at the
same horizontal position on the two waveforms because any voltage measurement has to take place with leads positioned at the same point in time. In this example
the red lead is at a higher potential than the black lead. The voltmeter reads that as a positive voltage. Now apply that frozen-in-time positive voltage to the top-left
blue circuit. The induced current will flow from the blue stator winding up through the diode and out the top of the rectifier to the positive battery terminal. The current
passes through the battery, charging it in the process, and exiting out the negative terminal. From there it enters the bottom of the rectifier, passes through the second
diode and enters the green stator winding completing the circuit. This same analysis can be performed for the other five 60° increments. In every case the current will
leave the top of the rectifier and reenter at the bottom. The current always travels in the same direction. That is how you convert 3-phase AC to DC.


The output waveform from the generator is always above the zero volt line. The current never goes negative so it's DC
but there is a small ripple voltage riding on the DC output. That's the whine you hear in the radio of some cars. That's
the noise signal the suppressor filter shorts to ground. The next step is regulate the generator's output voltage.

 

This is the solid-state voltage regulator found inside the generator.


The triangular device feeding the transistor is an op-amp with no feedback loop. This circuit
is called a comparator. This is how it works. The signal from the positive side of the battery
is fed to the non-inverting input (-) of the op-amp. If the battery voltage (which is the same
as the generator output) is less than 14 volts, the comparator swings the output voltage fully
positive. That huge positive voltage is fed to the base of the NPN transistor saturating it. It's
like closing a set of switch contacts between the two vertical transistor leads. Maximum
current flows through the rotor windings producing the maximum magnetic field. The rotating
magnetic field slices through the stator windings inducing current that charges the battery.
When the battery voltage exceeds 14 volts the comparator output swings low and turns the
transistor off. The rotor current disappears and the magnetic field vanishes. Without a rotating
magnetic field no current is induced in the stator. When the battery voltage once again drops
below 14 volts, the comparator output swings fully positive, the transistor switch turns on,
the rotor's magnetic field is reestablished, current is again induced in the stator and the
generator output voltage goes back up.


The output of the comparator is a series of pulses.


The actual regulator circuit is a little more complicated buts works on the same principle. According to the service manual the Tracker's pulses come at a fixed
rate of 400 per second. The rotor current is is proportional to the pulse width of the comparator output. This is why the IC regulator is said to use Pulse Width
Modulation (PWM).



You'd think if you only need 35 amps from a 70-amp generator you could just run the rotor control transistor at half current. The reason you don't is heat. If the
transistor is off, has passes no current so it's power dissipation (radiated heat) is practically zero. If the transistor is fully on, it's resistance is very low so it's
acting like a piece of wire and again does not generate a lot of heat. But in the middle of its range it has both current and resistance and that generates heat.
Not the kind of heat that is hot to the touch but the kind of heat that melts the semiconductor inside the transistor. The voltage regulator will last a lot longer
under PWM control than analog control.