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Now that it seems that you might be a victim of A/C connector
failure, I thought I'd take the opportunity to explain how the
alternator in SabMags are different which helps explain why those
connectors are so vulnerable. The alternators used in
automobiles, trucks and most motorcycles (such as your CB750)
until around ten or twelve years ago, are electromagnet
alternators whose power output is controlled by how much power
you put INTO the electromagnet located on the armature, typically
a few watts to around 30 watts. SabMags and many, if not most of
today's motorcycles are permanent magnet alternators, called so
because the electromagnet in the armature is replaced with
permanent magnets, which of course, use no power. Since these
permanent magnets are magnets all the time, SabMag alternators
are always running at full blast. In a car, the engine power to
turn the alternator is relative to the electricity being consumed
by its appliances at the time. In SabMags, the effort to turn the
alternator is always at maximum effort, regardless of whether you
are using a little or a lot of electricity. Essentially, the
alternator represents about a one horsepower load at all times,
at least when the alternator is above about 2,500 RPM. Below that
it is strictly proportional to RPM since the alternator is not
running at is optimal speed. The A/C power sent through the A/C cable is always its full
rated 380 watts of power. With a car alternator, the power on the
A/C cable would depend on how much is being consumed by the
target appliances. At the other end of the SabMag A/C cable is
the voltage regulator, but essentially it is a power regulator,
because it has an interesting task. If the sum of all SabMag
appliances don't need a full 380 watts of power, it must burn off
the power to keep the volatge from getting too high. It does this
by shorting the A/C wires together. This causes the alternator
field wires to heat up, which is carried away by the engine oil. The reason why permanent magnet alternators are used? Cost.
For applications where up to 500 watts are needed. Car
alternators usually have to deliver about 1,000 to 3,000 watts.
Delivering that much power in a permanent magnet alternator would
require the alternator to be huge and it would be all but
impossible to keep from smoking the field wires without oil
cooling. Since it only takes about 12 to 18 horsepower to push a motorcycle down a highway at about 65 mph, a load of one horsepower from a permanent magnet alternator is probably costing a motorcycle that gets about 40 MPG about an additional 2 MPG. |