Tài liệu học tập cơ bản khái quát về động cơ và các bộ phận trên ô tô phiên bản tiếng anh. Tài liệu này nhằm giúp chúng ta tiếp cận được cấu tạo chức năng của các bộ phận của xe. Với tài liệu này giúp các bạn sinh viên ngành cơ khí ô tô tiếp cận được những kiến thức cơ bản về ô tô và đồng thời nâng cao kiến thức tiếng anh. Bộ tài liệu này được soạn thảo bởi trường đào tạo và huấn luyện nghề ở Canada.
Chapter 18 Starting and Traction Motor Systems Types of Electric Motors • Electric motors are used to start the engine • In hybrid electric vehicles (HEVs), electric motors can used to propel the vehicle • Smaller electric motors are DC • Traction or drive motors are AC Basics of Electromagnetism Electromagnets • Natural magnets from magnetite • Artificial magnets rearrange molecules to align along North and South poles • Artificial magnets can be temporary or permanent • Current carrying wire generates a magnetic field Magnetic Circuits and Reluctance • Lines of flux can only occupy a closed magnetic circuit • The resistance to the passage of flux lines is called reluctance • Inserting an iron core into a coil increases the strength of the magnetic field Motors • • • • • • Convert electric energy into mechanical Use interactions of magnetic fields An electromagnet is fitted to a shaft Shaft surrounded by stationary fields Polarity of fields are switched Shaft rotation can work Basic Motor Operating Principles Control Circuit Voltage Drop • High resistance in solenoid switch circuit reduces current flow through solenoid windings • Disable the ignition system • Test between battery positive and starter switch terminal on solenoid or relay • Normally less than 0.5 volts Starter Drive Test • • • • • Checks for a slipping starter drive Bypass or disable the ignition Crank engine for several seconds Repeat at least three times If engine stops cranking but starter is still spinning, the starter drive is slipping Free Speed (No-Load) Test • Every starter should be bench tested when removed and before being installed • Firmly clamp starter in a vice • Connect ammeter to battery cable and starter to a battery • Check current draw and motor speed Installation • Sand paint from mounting point • Check starter clearance on starters that use shims High-Voltage Motors • Traction motors may drive vehicle or act as a starter/generator or add power output • HV motors can be liquid or air cooled • Most production vehicles use AC motors • Conversion vehicles use DC motors Brushless DC Motors • Similar to brushed DC motor • Rotor and stator are reversed • Current flow is switched to different stator windings • May use Hall-effect sensors to monitor rotor position AC Motors • • • • • Has two parts, the rotor and stator Stator has individual electromagnets Rotor is the rotating magnetic field Current passes from stator to rotor Three phase AC commonly used Rotor Sensors • AC motors require a rotor position sensor • Times or phases the three-phase AC • Control system monitors position and speed of the rotor and controls the frequency of stator voltage • This controls the torque and speed of the motor Inverters • AC supplied by an AC generator or through an inverter connected to the battery • Inverter changes high-voltage DC into highvoltage three phase AC • Also changes AC into DC to charge the battery pack Controllers • Manages the flow of electricity from the battery to the motors • A simple controller is a potentiometer • Controllers monitor input from sensors and controls the duty cycle of the voltage to the motor ... shunt motors – Compound or combination motors Starting System Components • Battery • Ignition switch • Cable and wires • Starter solenoid or relay • Starter motor • Starter safety switch Typical Starting. .. High-Voltage Motors • Traction motors may drive vehicle or act as a starter/generator or add power output • HV motors can be liquid or air cooled • Most production vehicles use AC motors • Conversion... switch, and starter solenoid or relay • Starting safety switch – Prevents vehicle from starting unless in park or neutral or with clutch disengaged Preliminary Checks • Check the battery and charge