_files/CAYBEV4B.jpg)
The
generator is located at the front RH side of the engine, in front of the RH
cylinder head. The generator has an output of 85/150 Amps and is manufactured by
Denso. A six-ribbed polyvee belt drives the generator pulley, which in turn is
driven from the engine crankshaft pulley.
The generator comprises a
stator, a rotor, a rectifier pack and a regulator. There is a three-pin
connector (C0053) on the generator:
- Pin 1 – Pulse Width Modulated (PWM) signal from the generator to the
Engine Control Module (ECM) (generator monitoring)
- Pin 2 – PWM signal from the ECM to the generator (generator control)
- Pin 3 – Voltage reference line to the battery via the Battery Junction Box
(BJB).
The generator is connected to ground via its
mountings.
The rotor comprises a field winding, wound around an iron core
and mounted on a shaft. The iron core has extensions at each end, which form
North and South poles as current flows through the field winding. The rotor is
located inside the stator and is mounted on bearings for smooth running and to
support the rotor due to the high side loading applied by the drive belt
tension.
The stator has three sets of coils made from copper wire. The
three coil windings are connected in a 'star' connection, where one end of the
winding is connected to the other two windings. The output current is supplied
from the opposite end of each winding. Rotation of the rotor causes ac current
to be produced in the coils.
The rectifier converts the ac current
produced in the stator coils into dc (rectified) current required by the vehicle
electrical system. The rectifier comprises semi-conductor diodes mounted on a
heatsink to dissipate heat. An equal number of the diodes are on the negative
and positive side, with an additional diode in the regulator to control the
feedback through the battery voltage signal line. The rectifier also prevents
current flow from the battery to the generator when the output voltage is less
than the battery voltage.
The 'smart' regulator controls the output
voltage from the generator to protect the battery; at low temperatures battery
charge acceptance is very poor so the voltage needs to be high to maximise any
re-chargeability, but at high temperatures the charge voltage must be restricted
to prevent excessive gassing at the battery with consequent water loss. The EMS,
which controls the regulator, will calculate the voltage set point required for
the ensuing conditions. The 'traditional' regulator controls voltage against
generator temperature, which means the battery temperature will lag a long way
behind so there will be significant periods of operation when battery charging
is compromised. With this system, the EMS can set the voltage by inferring the
battery temperature from information received from it's various sensors, hence
voltage will follow the battery's needs a lot more accurately.
The
regulator has transistors, which rapidly switch on and off to regulate the
voltage output according to the voltage sensed internally. The regulator also
provides a PWM signal output to the ECM, which uses the signal to adjust the
idle speed under varying electrical loads.
Initially, the ignition switch
supply provides an excitation current to the rotor at low generator speeds via
brushes, which contact slip rings at the end of the rotor shaft. As the
generator speed increases the generator becomes self-exciting.
The charge
warning lamp function is transmitted to the EMS and then on to the Controller
Area Network (CAN) bus to the instrument pack.
LOAD MANAGEMENT SYSTEM
The load management system comprises software
resident in the Automatic Temperature Control Module (ATCM).
Control Components (412-04 Control Components)
Its
purpose is to protect battery state-of-charge during abnormal usage of the
vehicle. The system will request the Media Orientated System Transport (MOST)
ring and the air suspension to go into 'power save' mode, and will modulate
features such as seat heating and screen heating to prevent the battery being
dragged down to a point where the car becomes unoperational. A 'WARNING - LOW
BATTERY' message will be displayed in the message centre.