Battery Powered Aircraft — Chapter 13

Flashcards covering the core concepts of battery powered aircraft from the notes, including motors, magnets, batteries, power electronics, safety, and cooling.

Why is an electric motor used in a battery powered aircraft instead of a piston engine, and what is the main trade-off?

Electric motors are typically lighter than piston engines, but the battery's limited energy storage limits the aircraft's flight range.

How does an electric motor generate rotational thrust to spin the propeller?

Electric energy is used to create a turning force via magnetism; magnets attract or repel to produce rotational motion of the rotor.

What are the two main types of magnets and where can they be located within a motor?

Permanent magnets and temporary magnets; they can be located in the stator (fixed outer part) or the rotor (rotating inner part) depending on the design.

What is a temporary magnet and when does it act like a magnet?

A magnet created when electric current flows through a conductor; it behaves as a magnet only while current flows, and stops magnetizing when the current stops.

What happens around a conductor when electric current flows through it?

A magnetic field is created around the conductor.

What are the roles of the stator and rotor in an electric motor?

The stator is the fixed outer part, and the rotor is the rotating inner part that turns and is connected to the propeller via a shaft.

How is continuous rotation achieved in a basic electric motor when the rotor would otherwise align with opposite poles and stop?

The motor flips the magnetic field in the rotor by reversing the current direction, so the rotor is continually attracted to the next opposite pole and keeps turning.

What is the function of a commutator in a DC motor?

It switches the direction of current through the rotor windings to flip the rotor's magnetic field and sustain rotation.

How do DC and AC motors differ in terms of magnet placement and operation?

DC motors typically have a permanent magnet in the stator with a winding and a commutator on the rotor; AC motors usually place the rotor with permanent magnets and use stator coils energized in sequence to create a rotating magnetic field.

What is the main downside of battery weight in aircraft, despite the motor’s lightweight advantage?

The battery’s weight largely offsets the motor’s weight savings, affecting overall aircraft performance and range.

What are the basic components of a battery cell?

Two electrodes (plates) of different materials, an electrolyte between them, and external terminals (positive and negative) for connection.

What is the difference between a primary and a secondary battery?

A primary battery is non-rechargeable; a secondary battery can be recharged by supplying electrical energy to reverse the chemical reaction.

Which rechargeable batteries are common in aircraft, and which is increasingly used for higher energy density?

Lead-acid and NiCad are common; lithium-ion batteries are increasingly used due to higher energy density and rechargeability.

How does lithium-ion energy density compare to lead-acid batteries?

Lithium-ion batteries can store about ten times more electricity than similarly sized lead-acid batteries.

What unit is often used to describe battery capacity in these notes, and what does it signify?

Kilowatts (kW); it relates to how much electricity the battery can store (and thus the potential flight duration/range).

What voltages are cited for typical batteries in this context, including AA and small piston aircraft batteries?

AA batteries ~1 volt; small piston aircraft batteries around 12 volts; high-voltage systems around 400 volts (and over 800 volts in some applications like electric cars).

Why is a high voltage supply used in battery powered aircraft?

To deliver sufficient electrical energy to the electric motor and other high-demand components given the energy storage limits.

What safety guidance is given regarding high voltage wiring in and around the aircraft?

High voltage is dangerous; always treat wires as if electricity is running through them and keep away from main areas, even when the aircraft is shut down.

What is the purpose of an inverter in a battery powered aircraft?

To convert DC from the battery into AC suitable for the electric motor.

What cooling considerations are important for battery-powered aircraft, and what does a typical cooling system include?

Cooling is essential for the motor, battery, and inverter; a liquid cooling system with a radiator and a pump circulates coolant to keep temperatures safe.