The main engine slows down, and the permanent magnet speed regulation energy-saving technology brings a new mode!

At present, the international shipping market is in a downturn. Due to factors such as fuel price, low speed economy and carbon emission, in order to reduce the total cost of ship operations, many ships in operation generally adopt the operation mode of the main engine (purchasing supply), but The running speed of the main engine means that the cooling water demand of the main cooling water pump is reduced, which is bound to reduce the speed of the cooling water pump motor. How to achieve the goal of speed reduction and energy saving of the ship's main engine cooling water pump is an important issue before the eyes of the shipowners.

         First of all, let us first understand the cooling water pump (centrifugal sea water pump, fresh water pump) of the ship's main engine. The main engine cooling water pump usually uses the motor as the prime mover, which is the equipment that consumes more energy on the ship. The cooling water pump often adjusts the displacement at any time according to the needs of the work.

         This requires adjustment of the operating point of the cooling water pump.

         I. Analysis of the status quo of the adjustment method of the working condition of the ship's main engine cooling water pump

         Bypass adjustment method

         Set the bypass line to work in parallel with the main line, and change the opening of the bypass line by changing the opening of the bypass valve (purchasing supply) to adjust the displacement of the main pipe of the pump.

         2. Throttling adjustment method

         When the cooling water pump is running at a constant speed, the opening degree of the discharge valve is changed to change the working condition of the pump to achieve the purpose of adjusting the displacement of the pump.

         3. Variable speed adjustment method (more frequency conversion adjustment)

         The variable speed prime mover is used to change the characteristics of the pump to adjust the displacement and pressure head to control the flow of the cooling pump of the ship's main engine.

         Among the above three adjustment methods, the first two methods have considerable energy loss in the throttling loss of the bypass line and the discharge valve opening degree, and the economy is poor. The shift adjustment method not only has a wide adjustment range, but also saves power, so that the operating efficiency of the pump is kept high.
         Second, the analysis of the problems existing in the variable frequency regulation technology in the energy-saving speed regulation of the ship's main engine cooling water pump

         Taking the third adjustment method as an example, combined with the current deployment status of the main engine cooling water pump prime mover, the main engine cooling water pump of the frequency conversion device has been installed, and the frequency of the main engine cooling water pump driving motor is reduced by the frequency conversion frequency reduction method, thereby reducing The amount of cooling water required, but the following problems exist:

         1. Large electromagnetic harmonic interference

         Inverters (purchasing supply in the product library) often generate a lot of interference electromagnetic waves when working. If these electromagnetic waves do not take appropriate precautions, they will affect the normal operation of the instrument (purchasing supply) and the radio communication equipment. The work will interfere.

         2. High ambient temperature and working temperature requirements

         The power and electronic components inside the inverter require a suitable operating temperature. The general requirement is 55 ° C or less. In the inverter inverter circuit, if the temperature exceeds a certain limit, the IGBT power tube will be damaged immediately. And because the ship environment is complex, the humidity is serious, the humidity is hot and humid, the water vapor is easy to condense, and the entry of thunderstorm, dust, oil, metal debris, etc. will also lead to the burning of non-insulated circuit boards, although the inverters for ships are more industrial. The degree of protection of the inverter is improved, and the special components are applied to the electrical components, but the requirements for the marine inverters are still not fully met.

         3. Vibration and shock have great influence on frequency conversion control

         If the inverter control cabinet is subjected to mechanical vibration or shock, it will often cause poor electrical contact, affecting the normal operation of the circuit. The ship is often subjected to vibration or impact due to wind and waves. Therefore, the marine inverter control cabinet must have a certain mechanical strength. Keep away from vibration sources and shock sources during installation, and apply anti-vibration rubber pads for fixing.

         4. Grounding requirements

         Proper grounding of the inverter is an important means to improve the sensitivity of the system and suppress noise. The grounding resistance of the grounding terminal of the inverter is as small as possible. It must be separated from the grounding point of the power equipment and cannot be grounded. The shield of the input signal line should be connected to the inverter ground terminal E (G).

         The main engine cooling water pump without frequency converter and other speed control devices, because the main engine reduces the running speed, the cooling water demand is reduced, because the main engine cooling water pump is not equipped with any speed control device, which means that the cooling water pump will be at full load. Under the operation, this working state has serious non-energy saving, and it is a realistic problem faced by most current shipping ships.

         Then we can't help but ask, is there a kind of speed-saving energy-saving technology that can realize all the functions of frequency conversion speed regulation, and has not such a harsh environment and installation requirements?

         Next, let's take a look at the permanent magnet speed-saving energy-saving technology.

         Third, permanent magnet speed control energy-saving technology analysis

         1. Overview of permanent magnet speed control technology

         The rated parameters of most centrifugal pumps and fans (purchased by the product warehouse) are larger than the actual demand, and the pumps and fans are in constant speed operation all the year round. Usually, the required flow and pressure are adjusted by valves or dampers, and a large amount of energy is consumed. In terms of the increased resistance of the valve or damper, it is extremely uneconomical and less in line with the national call for energy conservation.
         A breakthrough new technology developed by the permanent magnet drive technology in recent years is a suitable technology for speed regulation and energy saving of centrifugal loads of fans and pumps. It is a new transmission technology developed rapidly in permanent magnet new material technology, permanent magnet transmission technology, machinery manufacturing and design level. It has high efficiency, energy saving, high reliability, no rigid connection transmission torque, and can be applied in harsh environments. Greatly reduce overall system vibration, reduce system maintenance and extend system life. In particular, its excellent speed regulation characteristics that do not generate high-order harmonics and do not cause motor heating at low speed make it the first choice for energy-saving technical transformation of fans and pumps.

         2. The composition and working principle of permanent magnet speed control system

         The permanent magnet governor is a revolutionary transmission device that transmits torque through the air gap. There is no need for mechanical connection between the motor and the shaft of the load device. When the motor rotates, the guide disk is driven by a strong magnetic field generated by a disk containing a strong rare earth magnet. Cutting (product library purchase) magnetic lines, thus generating eddy currents in the conductive disk, the eddy current generates an anti-inductive magnetic field on the conductive disk, pulling the relative movement of the conductive disk and the disk, thereby realizing the torque transmission between the motor and the load .

         The permanent magnet governor consists of four components:

         Permanent magnet rotor: aluminum disc with permanent magnets (strong rare earth magnet) connected to the load shaft

         Magnetically permeable rotor: magnetizer disk (copper or aluminum), connected to the motor shaft

         Air gap actuator: mechanism for adjusting the air gap between the disk and the guide disk

         Rotary shaft connecting shell and shrinking disc: connecting with motor and load shaft with patented shrinking disc device

         The main engine slows down, and the permanent magnet speed regulation energy-saving technology brings a new mode!

         Permanent magnet governor structure

         The main engine slows down, and the permanent magnet speed regulation energy-saving technology brings a new mode!

         Permanent magnet governor physical map

         3. Comparison and analysis of application of permanent magnet speed regulation and frequency conversion speed regulation technology

         a. Impact on the ship's original grid

         Frequency control: The variable frequency speed is to change the input voltage to the high voltage DC voltage through the inverter input rectifier, and then convert the inverter into a high frequency alternating current with variable frequency to change the frequency to drive the motor to run. Speed ​​technology. Because the input end of the inverter is directly connected to the power grid, it is more sensitive to the grid voltage. The ship's navigation voltage changes, current changes, lightning surges, and sea conditions are complex, which directly affect the reliability of the inverter electronic equipment and easily cause the inverter's insulation. Wear, control device damage, etc., so it has the lowest safety, greatly reducing the reliability of the original system, in order to improve reliability, additional lightning protection devices are required.

         Permanent magnet speed regulation: The permanent magnet speed control equipment is a precision purely mechanical equipment, which adopts the load slip speed regulation technology. There is no complicated speed control equipment and system, and it is not necessary to access the original ship to control the power grid, so it is not sensitive to the grid voltage and does not affect the reliability of the ship's original grid system.

         b. Reconstruction requirements for the motor and installation method of the main engine cooling water system of the ship

         Frequency control: Since the output voltage of the inverter is a sine wave composed of many square waves superposed, there is a large harmonic component, and the high harmonic current is very large, which easily leads to overheating of the motor (because of the skin effect). Therefore, strictly speaking, the motor should use a variable frequency motor with insulation class H to ensure the design life of the original motor. Generally, the existing modification ignores the influence of the inverter on the life of the motor and directly uses the existing motor, which is very unreasonable. of. If the ship's main engine cooling water source drive motor has not yet adopted a variable frequency motor, additional frequency conversion motors are required.

         Permanent magnet speed regulation: Because the equipment is driven by the main motor of the ship's original cooling water pump, there is no special requirement for the cooling water pump drive motor. Flexible installation, vertical and horizontal installation.

         The main engine slows down, and the permanent magnet speed regulation energy-saving technology brings a new mode!

         Vertical installation

         The main engine slows down, and the permanent magnet speed regulation energy-saving technology brings a new mode!

         Horizontal installation

         c. Environmental requirements for the ship

         Frequency control: The inverter is a complex power electronic device. The control circuit uses thyristor or IGBT to achieve current regulation. The semiconductor components are usually required to work in the environment of 0~55 °C, and the ambient humidity is also required, generally the relative humidity. 60~90%, therefore, it is necessary to provide a dedicated room for the speed control equipment and install the air conditioner (the product library is available for purchase).

         Permanent magnet speed regulation: The permanent magnet speed control device is a precision pure mechanical device, which is allowed to work in the environment of -50~+100°C, and even works in the environment of 0~100% relative humidity. Generally, it does not need to provide any environmental conditions.

         d. Influence on motor start

         Frequency control: The inverter can start from 0 speed, but the load is always loaded during the startup process. The starting time is very long. During the starting process, the motor is in low speed. The motor generates heat, but the starting current is small and the pipeline pressure increases steadily. Does not cause a sudden change in line pressure.

         Permanent magnet speed regulation: When the motor starts, the load can be completely disconnected to achieve zero load start. When the motor speed reaches full speed quickly, the load starts smoothly, the starting time is short, the current impact is small and the pipeline pressure increases steadily, which will not cause The line pressure is abrupt.

         e. Effects of power harmonics and power factors

         Frequency control: The inverter is directly connected in series between the ship's grid side and the motor, and is input by rectification. Therefore, a very high frequency range harmonic current is generated in the grid, and the total harmonics usually generated by the inverter The current should exceed 60%; due to the harmonic current, the power factor compensation capacitor is often burnt, the fuse is blown, the air switch trips, and the line is overloaded. In order to prevent the above failures, it is usually necessary to invest in expensive harmonic control equipment.

         Permanent magnet speed regulation: Since it is independent of the grid, no harmonics are generated.

         f. Speed ​​regulation reliability

         Frequency conversion speed regulation: The frequency converter is composed of rectification and filtering circuit + variable frequency inverter circuit + complex control electronic circuit, especially its main circuit. In order to use low voltage high frequency power device, it has to adopt multi-stage series conversion power circuit, circuit The number of components is in the thousands, so its reliability is the lowest, usually MTBF is less than 10 years.

         Permanent magnet speed regulation: The permanent magnet speed control device consists of three parts. The copper plate + permanent iron plate + gap adjustment servo mechanism has a very simple structure, so the reliability is very high. Generally, the MTBF can exceed 10 years.

         g. Impact of ship navigation vibration on system failure rate

         Inverter: The sea state of the ship is changing rapidly. Because the frequency conversion technology does not change the mechanical connection mode (rigid direct connection) of the original fan pump system, the vibration, deformation, impact and noise of the system during the ship navigation are completely dependent on the motor and the fan or pump. The mechanical mounting accuracy, that is, the accuracy of the shaft alignment, places great demands on the mounting accuracy.

         Permanent magnet speed regulation: the air gap is used to transmit torque. The cooling water pump and the drive motor have no rigid coupling. The possibility of transmission, shock and noise transmission of the system is greatly reduced, and the relationship with the installation accuracy is very small. Under the vibration, the vibration can be reduced by 80%; thus the mechanical energy consumption and wear are greatly reduced, the error tolerance of the shaft alignment precision is large, and the installation and maintenance are very convenient and quick.

         h. Post-maintenance maintenance workload and difficulty

         Inverter: For the above reasons, the reliability of the variable frequency speed control system is relatively low and it is highly susceptible to the changing environment of the sea. The failure rate is high, and because of its complicated technology, difficult fault diagnosis and high maintenance technical requirements. Therefore, the maintenance time and the MTTR are greatly increased, the maintenance and repair costs are high, and the assistance of the original technical personnel is required, which further reduces the availability of the system.

         Permanent speed: purely mechanical equipment, high reliability and virtually unaffected by ships at sea and environmental conditions of the host, and can greatly reduce vibration, the failure probability is very low, and because the technology is simple, easy to diagnose faults, maintenance technology low requirements, maintenance time is very short and very low MTTR, system availability is high.

         In summary, in the context of a ship Low Speed, saving energy is of great significance to the sustainable and healthy development of the whole shipping industry, combined ship main cooling water pump energy-saving and practical needs of the actual situation, through the inverter control technology in ship analysis on the main cooling water pumps, illustrates the permanent control technology has great advantages in energy-saving cooling water pump of the host ship, we believe that with the permanent control technology in coal, electricity, petroleum, chemical, metallurgy, continuous application and technology accumulation shipbuilding and other industries, this new energy-saving technology, is bound to bring an efficient, environmentally friendly and reliable new model for a host of energy-saving cooling water pump ship!

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