As we all know, a ship is composed of many parts, which can be summarized into three parts: hull, ship power plant, and ship electrical. The ship power is mainly the propulsion device: the main engine is driven by the deceleration device and the transmission shaft system to drive the propeller with screw propeller as the main form.

　　The electric propulsion system, as the name implies, is a motor that provides mechanical power to the propeller. There are roughly three types of marine drive systems:

　　(1) The method of connecting the electric motor and the internal combustion engine to the same shaft to provide mechanical power to the propeller. This system can not only improve operating efficiency, but also maintain the traditional way of propulsion. At low speeds or when starting, electric drives are more efficient than internal combustion engines.

　　(2) The all-electric drive thruster system uses batteries (it is better to use lithium iron phosphate electromagnetic instead of lead-acid batteries) or other power generation devices that may appear in the future to provide power to the thrusters. It has energy storage limitations and can only be used in low-power and short-range applications, such as ferries.

　　(3) The way in which gas turbines or diesel internal combustion engines are used to generate electricity, and the electricity is delivered to various work loads and propulsion systems on board. There is no need for a mechanical connection between the source power of the propulsion system and the propeller, and there are many advantages and potentials that can be developed.

　　Through investigations, it is found that the technological innovation of modern ships in recent years is particularly reflected in the gradual increase in electric propulsion systems. The advantages of the electric drive propulsion system are to reduce maintenance work, reduce fuel consumption, and contribute to emission reduction targets, and so on.

　　The most common motors on the market are cast aluminum rotors and cast copper rotors. Since the resistance of aluminum is higher than that of copper, the cast aluminum rotor directly affects the resistance of the rotor, which has a great impact on the starting performance, rated speed, motor size, weight, etc. of the motor.

　　The cast copper rotor has the following advantages: (1) The total loss is significantly reduced, thereby improving the overall efficiency of the motor, reaching IE4 or even IE5 energy efficiency level. (2) Significantly reduce the temperature rise of the motor, thereby improving the reliability and service life of the motor. (3) Use a smaller fan or even no fan, which reduces vibration and noise. (4) It can provide more flexible design space for the design and manufacture of electric motors, which can pursue high efficiency, low cost, small size, light weight, etc., or a balance between these. (5) Improve production efficiency, reduce production costs, and improve product quality stability.

　　According to data, among all the technologies and methods for improving the electrical efficiency of small and medium-sized squirrel cage motors, the use of copper rotors instead of aluminum rotor die-casting technology is considered to be one of the best ways. It is believed that copper rotors will gradually become popular in the ship propulsion field. In the future, the motors in electric propulsion systems will soon usher in the "copper rotor era".

　　Lithium-ion battery (LIB) has become the main energy storage solution in modern social life. Among them, lithium iron phosphate batteries are a perfect replacement for lead-acid batteries, and they are the first choice for grid-connected peak shaving, off-grid energy storage, photovoltaic energy storage, UPS, data center and other industries.

　　The motor system is matched with a high-rate performance lithium battery system, which is a very promising way to use it.