We are starting a new chapter — Chapter 7, DC Electrics — DC Motors — Page 102, Lesson 101

We are starting a new chapter — Chapter 7, DC Electrics — DC Motors. This chapter covers the construction, operation, and application of DC motors and their associated systems in aircraft. Let me walk you through the topics we will cover. First, we begin with Electric Motors — the fundamental principle of converting electrical energy into mechanical motion. Then we move to Fleming’s Left Hand Rule, which is the rule that tells us the direction of motion in a motor when we know the direction of current and magnetic field. Next, we look at the Practical DC Motor — how a real motor is built, with its armature, field windings, brushes, and commutator. Then we study Back EMF — the voltage generated inside the motor that opposes the applied voltage and limits current as the motor speeds up. We then cover the Slow Start Resistor — a resistor placed in series with the motor to limit inrush current during startup, protecting the motor and the electrical system. After that, Commutation — the process by which the commutator and brushes reverse the current in the armature coils to keep the motor turning in one direction. We then compare two types of DC motors: Series Wound Motors and Shunt Wound Motors. Series wound motors have the field winding in series with the armature, giving high starting torque but poor speed regulation. Shunt wound motors have the field winding in parallel with the armature, giving good speed regulation but lower starting torque. Next, Starter-generator Systems — a single machine that acts as a starter motor to crank the engine and then as a generator to produce electrical power once the engine is running. This is common on turbine aircraft. Then we move to Actuators — devices that convert electrical energy into mechanical movement to operate things like flight controls, landing gear, and valves. We start with Solenoid Actuators — simple on/off devices using a coil and a moving plunger. Then Motor Actuator Construction — how a motor is built into an actuator assembly. We then study The Split Field Series Actuator — a special type of motor actuator that can reverse direction by switching which half of the field winding is energized. We cover its construction and then its Operation — how it moves in one direction or the other depending on which field coil is powered. Next, Motor Actuators in general, then Rotary Actuators — which produce rotational motion, and Linear Actuators — which produce straight-line motion. Linear actuators appear twice in the list, so we will cover them thoroughly. We then look at Actuator Brakes — devices that hold the actuator in position when power is removed, and Actuator Clutches — which allow the actuator to disengage from the load under certain conditions. Finally, we cover the indicators that tell the pilot or crew the position of the actuator: Visual Indicators Used with Linear Actuators, Visual Indicators Used with Rotary Actuators, Indicator Lights, and Electromagnetic Indicators. The chapter ends with Questions and Answers for self-testing. That is the full roadmap for Chapter 7. We will go through each topic in detail, starting with electric motors and Fleming’s Left Hand Rule.