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https://www.magicmag-tech.com/Advantages-of-magnetic-couplings-on-induced-draft-fans.html
Currently, the boiler host, its high-power blowers and induced draft fan used by most of the speed control method is frequency conversion speed control. In view of the frequency conversion governor in the boiler production and operation problems, especially the uncertainty of the frequency conversion equipment failure, directly affecting the production and operation of the continuity, stability, and reliability;, this loss is usually due to the failure of electrical equipment failure, processing is not timely resulting in furnace stoppage, shutdown. And the use of high-power speed type magnetic coupler (ASD) speed program to replace the current frequency converter speed program (i.e., change the indirect control to direct control form), you can get the use of frequency converter speed program is incomparable to the absolute advantage.
Magnetic coupler is also known as magnetic coupling, permanent magnet transmission device. Magnetic coupler transmission device mainly consists of three parts: copper rotor, permanent magnet rotor and controller. Generally, the copper rotor is connected to the motor shaft, and the permanent magnet rotor is connected to the shaft of the working machine. There is an air gap (called air gap) between the copper rotor and the permanent magnet rotor, and there is no mechanical connection for transmitting torque. In this way, a soft (magnetic) connection is formed between the motor and the working machine, and changes in torque and speed of the working machine shaft are realized by adjusting the air gap. The structure is shown in the figure:
Let's analyze and compare its advantages and disadvantages:
(1) System Reliability
Magnetic coupler
Magnetic coupler is a purely mechanical product with stable performance, no requirement for power supply and no high harmonic pollution to the power grid in use. Because no electricity is used, there is no electromagnetic interference problem.
High-voltage inverter
Although the frequency converter (most of the induced draft fan with 6000V or 10000V high-voltage frequency converter) technology is relatively over the top, but as a highly complex electronic equipment, the operation of the failure of the unpredictability, uncertainty is still there for all to see. First of all, the environmental requirements are very harsh, special rooms to be sealed, dust-proof, summer air conditioning to maintain the normal operation of the equipment required by the temperature, auxiliary facilities to invest more. Secondly, there are certain requirements for the power supply, electronic equipment susceptible to electromagnetic interference will cause unreliable operation of inverter equipment. At the same time, due to the use of frequency converters, the shaft connection between the motor and the load (induced draft fan) is contact type, does not have the advantage of reducing bearing and seal damage.
(2) Stability of long-term operation
Magnetic coupler
Magnetic coupler has a simple mechanical structure, once the installation is completed and put into use, it is basically not subject to the interference and influence of the use of the environment, stable and reliable operation. Because no electricity is used, there is no problem of electromagnetic interference. Due to the use of magnetic coupler, the motor and load (induced draft fan) between the shaft connection is non-contact, therefore, the load (induced draft fan) vibration will not be transferred to the motor; but also because of the shaft connection is non-contact, so it brings two aspects of the benefits, one is the installation of the “alignment” requirements are low; two is in long-term operation will not be The second is that in long-term operation will not produce because of the direct shaft connection and brought about by the damage to the bearings, seals, to ensure that the use of equipment. As a pure mechanical equipment, its possible operational failures are predictable, not because of sudden failures and bring the user unprepared for the accident.
High voltage inverter
The core of the frequency converter is a complex electronic device, after the installation is completed and put into operation, it is susceptible to the interference and influence of the use of the environment, and it is difficult to ensure its stable and reliable operation. According to the use of most thermal power plants survey, inverter in the process of use, the average annual failure, long-term operational stability is very poor. As a complex electronic equipment, its operation failure is unforeseeable, it will be due to sudden failure and bring the user unprepared for the accident.
(3) Initial installation and later maintainability
Magnetic coupler
The structure is simple, the shaft connection between the motor and the load is non-contact, the requirement for the accuracy of the center is low, the installation and debugging is fast. Because it is pure mechanical equipment, no complex electronic equipment; after simple training, our electromechanical maintenance workers will quickly determine the cause of the failure and quickly solve the problem by themselves, without having to ask a professional company to repair.
Medium Voltage Inverter
Frequency converter is a complex electronic equipment, once an electrical failure occurs (frequent, unpredictable), our maintenance staff will be difficult to quickly determine the cause of the failure, and involves the replacement of spare parts, it is impossible to quickly solve the problem by themselves, can only be sent by the manufacturer of the frequency converter or a professional company to repair the problem, it is difficult to ensure that the rapid repair, does not affect production. The longest service life of the inverter is only 7 to 10 years.
(4) Economic analysis
Magnetic coupler
1. Initial investment
The initial investment in a magnetic coupler is currently about the same as that in an inverter.
2. Maintenance costs
Since the magnetic coupler is basically maintenance-free, the maintenance cost is almost zero;
3. Economic losses due to malfunctions
Although the magnetic coupler and frequency converter are energy-saving devices, the magnetic coupler is real for users to see the benefits of energy saving.
4. Maintenance and spare parts costs
Because the magnetic coupler is basically maintenance-free, the cost of repairing spare parts is almost zero.
Medium Voltage Inverter
1. Initial investment
The initial investment of the inverter is comparable to that of the magnetic coupler.
2. Maintenance costs
On average, there is a failure every year, and each time the maintenance and labor costs are worth a lot of money. And because of the uncertainty of its failure, the production losses caused by the larger.
3. Failure caused by the economic losses
Although the frequency converter is also energy-saving equipment, however, the frequency converter can not actually let the user see the benefits of energy saving, the reason is that its average time without failure is too short.
4. Maintenance spare parts costs
In order to ensure that the frequency converter sudden failure of production is not affected, the frequency converter spare parts usually have to prepare some of the full, which results in the occupation of funds, and because of the uncertainty of the failure, often occurring spare parts are not used all year round. As electronic components have a certain degree of timeliness, so the expired spare parts can only be scrapped, resulting in a waste of funds.
From the previous analysis can be seen, whether it is the immediate economic benefits, or from the perspective of long-term economic returns to consider, the magnetic coupler has a much more superior than the frequency converter of economic.
https://www.magicmag-tech.com/Advantages-of-magnetic-couplings-on-induced-draft-fans.html
SHANGHAI GAOLV E&M Technology Co.,Ltd.
