Q1) Research and explain why lithium-ion (Li-ion) batteries surpass the performance of
Nickel-Cadmium (Ni-Cd) and Lead Acid batteries. In your answer, include the following
information, stating any sources used.
1. Li-ion battery characteristics, applications and construction.
2. Advantages and Disadvantages of Li-ion battery
3. Why Li-ion battery is better than Ni-Cd and Lead Acid battery?
1.1)
Lithium-ion (Li-ion) batteries are rechargeable storage devices that move lithium ions
between the cathode and the anode. These batteries are made up of a lithium-based
cathode, a graphite anode, and an electrolyte. They are widely used in mobile phones,
electric vehicles, deep-cycle 4x4 batteries, home solar batteries, Teslar batteries, and
the aviation industry. Li-ion batteries have multiple cells, each with a negative
electrode (anode), a positive electrode (cathode), a separator and an electrolyte. The
cathode is sometimes made from lithium cobalt oxide or lithium iron phosphate,
lithium nickel manganese cobalt oxide. In contrast, the anode can be graphite, lithium
titanate, and silicon-based.
1.2)
Advantages of Li-ion batteries include high energy density, low self-discharge rate,
no battery memory effect, long cycle life, fast charging capabilities, and lightweight
design. Disadvantages include higher initial cost, potential safety concerns (risk of
thermal runaway, fumes produced from failed battery), sensitivity to extreme
temperatures, and gradual capacity loss over time.
1.3)
Li-ion batteries surpass Ni-Cd and Lead Acid batteries in ways. They have a much
higher energy density and are smaller and lighter in size and weight. Li-ion batteries
typically have a longer cycle life and a lower self-discharge rate, maintaining their
charge better when not used. They are more environmentally friendly, containing no
toxic metals like cadmium or lead. Li-ion batteries can be charged faster and don't
suffer from the memory effect, unlike Ni-Cd batteries.
Q2) Two 28 V batteries are connected in parallel, and each has a capacity rating of 120 AH.
During an emergency, the total load capacity is 75 % of the total holding capacity. Calculate
the total time of the battery capacity in hours and minutes.
2x120=240AH
240AH x 0.75= 180 AH
1 Hour and 20 Minutes @ 75% load
Q3) Research three (3) types of aircraft AC and DC motors. Report your findings explaining
the applications, operating systems and any limitations associated with the motors.
Brushless DC motors are used in aircraft systems due to their high efficiency, reliability, and
low maintenance requirements. These motors operate using electronic commutation instead
of mechanical brushes, used in fuel pumps, hydraulic pumps, helicopter blade fold motors
and environmental control systems. They offer precise speed control and high torque-toweight ratios, making them good for compact spaces within aircraft. Brushless DC motors
require intricate control electronics, which can increase overall system cost and complexity.
Synchronous AC motors are found in aircraft generators and constant-speed drive systems.
These motors operate at a speed synchronised with the frequency of the AC power supply,
giving a stable and consistent power output. They are useful in applications where
maintaining a constant speed is crucial, such as in engine-driven generators. Synchronous
motors offer high efficiency and power factor correction capabilities. They typically require
an external starting mechanism and may have difficulty starting under heavy loads.
Induction AC motors are used in aircraft systems, including air conditioning compressors,
cabin pressurisation systems, and some hydraulic pumps. These motors are known for their
simplicity, toughness, and low maintenance requirements. Induction motors operate based on
electromagnetic induction, eliminating the need for brushes or complex control systems.
They are cost-effective and can handle high starting torques. Induction motors may have
lower efficiency than brushless DC motors, especially at lower speeds, and their speed
control is less precise without using variable frequency drives.
Q4)
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