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Charging Systems: Summary
- The most common method of stator connection is called the wye connection. In the wye connection, one lead from each winding is connected to one common junction. From this junction, the other leads branch out in a Y pattern.
- Another method of stator connection is called the delta connection. The delta connection connects the lead of one end of the winding to the lead at the other end of the next winding.
- The diode rectifier bridge provides reasonably constant DC voltage to the vehicle’s electrical system and battery. Hie diode rectifier bridge is used to change the current in an AC generator.
- The converting of AC current to DC current is called rectification.
- The three principal circuits used in the AC generator are the charging circuit, which consists of the stator windings and rectifier circuits; the excitation circuit, which consists of the rotor field coil and the electrical connections to the coil; and the preexcitation circuit, which supplies the initial current for the field coil that starts the buildup of the magnetic field.
- The voltage regulator controls the output voltage of the AC generator, based on charging system demands, by controlling field current. The higher the field current, the higher the output voltage.
- The regulator must have system voltage as an input in order to regulate the output voltage. The input voltage to the regulator is called sensing voltage.
- Because ambient temperatures influence the rate of charge that a battery can accept, regulators are temperature compensated.
- The A circuit is called an external grounded field circuit and is always an electronic-type regulator. In the A circuit, the regulator is on the ground side of the field coil. The B+ for the field coil is picked up from inside the AC generator.
- Usually the В circuit regulator is mounted externally of the AC generator. The В circuit is an internally grounded circuit. In the В circuit, the voltage regulator controls the power side of the field circuit.
- Isolated field AC generators pick up B+ and ground externally. The AC generator has two field wires attached to the outside of the case. The voltage regulator can be located either on the ground (A circuit) or on the B+ (B circuit) side.
- An electronic regulator uses solid-state circuitry to perform the regulatory functions using a zener diode that blocks current flow until a specific voltage is obtained, at which point it allows the current to flow.
- On most modern vehicles, the regulator function has been incorporated into the vehicle’s engine computer. Regulation of the field circuit is through the ground (A circuit).
- There are three basic methods of informing the driver of the charging system’s condition: indicator lamps, ammeter, and voltmeter.
- Most indicator lamps operate on the basis of voltage drop. If the charging system output is less than battery voltage, there is an electrical potential difference in the lamp circuit and the lamp will light.
- The ammeter measures charging and discharging current in amperes. The ammeter is wired in series between the AC generator and the battery.
- The voltmeter is usually connected between the battery’s positive and negative terminals.
- The hybrid AC generator design consists of a rotor assembly with both wire wound and permanent magnet sections. The permanent magnets are located between the pole pieces of the rotor.
- The IGS is a three-phase AC motor that can provide power and torque to the vehicle that can also generate voltage whenever the rotor is turning.
- Generation is done anytime the engine is running.
- During vehicle deceleration the ISG regenerates the power that is used to slow the vehicle to recharge the HV and auxiliary batteries.
- The AC motors used in full hybrid vehicles can be used as generators whenever the engine is running and during vehicle deceleration.
- Generation can also occur whenever one of the motors slips. Hie slipping causes a cutting of the magnetic field and results in AC current. This current is used to supply electrical energy to the other motor.
- During vehicle coast conditions the electric motors are being turned by the wheels, and act as generators to recharge the HV battery. If additional vehicle deceleration is required, the hybrid controller can increase the force required to turn the electric motors.
- The AC voltage from the motors during regenerative or charging modes is rectified by the inverter module. Since this module converts the high AC voltage into high DC voltage to recharge the HV battery.
- The DC/DC converter allows the conversion of electrical power between the HV system and the low voltage (LV) system and replaces the function of the engine driven generator while maintaining isolation of the HV system.