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High Performance Low Maintenance Interior Permanent Magnet Motor
Analysis of the principle of the technical advantages of permanent magnet motor
The principle of a permanent magnet synchronous motor is as follows: In the motor's stator winding into the three-phase current, after the pass-in current, it will form a rotating magnetic field for the motor's stator winding. Because the rotor is installed with the permanent magnet, the permanent magnet's magnetic pole is fixed, according to the principle of magnetic poles of the same phase attracting different repulsion, the rotating magnetic field generated in the stator will drive the rotor to rotate, The rotation speed of the rotor is equal to the speed of the rotating pole produced in the stator.
Differences Between The Permanent Magnet Motor And Asynchronous Motor:
01. Rotor Structure
Asynchronous motor: The rotor consists of an iron core and a winding, mainly squirrel-cage and wire-wound rotors. A squirrel-cage rotor is cast with aluminum bars. The magnetic field of the aluminum bar cutting the stator drives the rotor.
PMSM Motor: The permanent magnets are embedded in the rotor magnetic poles, and are driven to rotate by the rotating magnetic field generated in the stator according to the principle of magnetic poles of the same phase attracting different repulsions.
02. Efficiency
Asynchronous motors: Need to absorb current from the grid excitation, resulting in a certain amount of energy loss, motor reactive current, and low power factor.
PMSM Motor: The magnetic field is provided by permanent magnets, the rotor does not need exciting current, and the motor efficiency is improved.
03. Volume And Weight
The use of high-performance permanent magnet materials makes the air gap magnetic field of permanent magnet synchronous motors larger than that of asynchronous motors. The size and weight are reduced compared to asynchronous motors. It will be one or two frame sizes lower than asynchronous motors.
04. Motor Starting Current
Asynchronous motor: It is directly started by power frequency electricity, and the starting current is large, which can reach 5 to 7 times the rated current, which has a great impact on the power grid in an instant. The large starting current causes the leakage resistance voltage drop of the stator winding to increase, and the starting torque is small so heavy-duty starting cannot be achieved. Even if the inverter is used, it can only start within the rated output current range.
PMSM Motor: It is driven by a dedicated controller, which lacks the rated output requirements of the reducer. The actual starting current is small, the current is gradually increased according to the load, and the starting torque is large.
05. Power Factor
Asynchronous motors have a low power factor, they must absorb a large amount of reactive current from the power grid, the large starting current of asynchronous motors will cause a short-term impact on the power grid, and long-term use will cause certain damage to the power grid equipment and transformers. It is necessary to add power compensation units and perform reactive power compensation to ensure the quality of the power grid and increase the cost of equipment use.
There is no induced current in the rotor of the permanent magnet synchronous motor, and the power factor of the motor is high, which improves the quality factor of the power grid and eliminates the need to install a compensator.
06. Maintenance
Asynchronous motor + reducer structure will generate vibration, heat, high failure rate, large lubricant consumption, and high manual maintenance cost; it will cause certain downtime losses.
The three-phase Permanent magnet synchronous motor drives the equipment directly. Because the reducer is eliminated, the motor output speed is low, mechanical noise is low, mechanical vibration is small, and the failure rate is low. The entire drive system is almost maintenance-free.
The three-phase Permanent magnet synchronous motor drives the equipment directly. Because the reducer is eliminated, the motor output speed is low, mechanical noise is low, mechanical vibration is small, and the failure rate is low. The entire drive system is almost maintenance-free.
The motor is excited by rare earth neodymium iron boron permanent magnet materials and is supplied with a permanent magnet special frequency converter. It has the characteristics of large starting torque, wide speed range, compact structure, small size, lightweight, low noise, high power factor, and high efficiency. It is an ideal power choice for high-efficiency and energy-saving air compressors.
1. The motor can operate normally under the following conditions:
1.1 The ambient temperature does not exceed 40℃;
1.2 Relative humidity ≤90%;
1.3 The altitude does not exceed 1000m.
2. The rated voltage of the motor is 380V, also according to user requirements.
3. The reference work system of the motor: S1.
4. Insulation grade: F grade.
5. Protection level: IP55.
6. Motor structure and installation type: B3, B35.
7. The motor outlet is located on the top of the base, or it can be located on the right or left of the base according to user requirements.
8. Motor service factor: 1.15, 1.2 (or as per technical agreement).
Advantages Of Rare-earth Permanent Magnet Motors
High efficiency: The efficiency curve of the asynchronous motor generally falls faster under 60% of the rated load, and the efficiency is very low at light load. The efficiency curve of the rare earth permanent magnet motor is high and flat, and it is in the high efficiency area at 20%~120% of the rated load.
High power factor: The measured value of the power factor of the rare earth permanent magnet synchronous motor is close to the limit value of 1.0. The power factor curve is as high and flat as the efficiency curve. The power factor is high. Low-voltage reactive power compensation is not required and the power distribution system capacity is fully utilized.
Stator current is small: The rotor has no excitation current, the reactive power is reduced, and the stator current is significantly reduced. Compared with the asynchronous motor of the same capacity, the stator current value can be reduced by 30% to 50%. At the same time, because the stator current is greatly reduced, the motor temperature rise is reduced, and the bearing grease and bearing life are extended.
High out-of-step torque and pull-in torque: Rare earth permanent magnet synchronous motors have higher out-of-step torque and pull-in torque, which makes the motor have higher load capacity and can be smoothly pulled into synchronization.
Disadvantages Of Rare-earth Permanent Magnet Motors
High cost: Compared with the asynchronous motor of the same specification, the air gap between the stator and the rotor is smaller, and the processing accuracy of each component is high; the rotor structure is more complicated and the price of rare earth magnetic steel material is high; therefore, the motor manufacturing cost is high, which is common for asynchronous motors About 2 times.
Large impact at full power start: When starting at full pressure, the synchronous speed can be drawn in a very short time. The mechanical shock is large. The starting current is more than 10 times the rated current. The impact on the power supply system is large, requiring a large capacity of the power supply system.
Rare-earth magnet steel is easy to demagnetize: When the permanent magnet material is subjected to vibration, high temperature and overload current, its magnetic permeability may decrease, or demagnetization phenomenon occurs, which reduces the performance of the permanent magnet motor.
I. Operation and use
1. Before the motor is energized, confirm the rotation direction of the motor, and check whether the mechanical installation and electrical connection are safe and reliable.
2. If abnormal noise or vibration is found in the motor during operation, please stop the operation immediately and cut off the power supply. Check the motor and compressor, and put it into operation again after troubleshooting.
3. If the temperature rise of the motor is found to be abnormal during operation, please stop the motor and cut off the power immediately, check the motor and the compressor, and then put it into use again after troubleshooting.
II. Maintenance
1. Please carry out regular maintenance of the bearing strictly in accordance with the bearing lubrication indication plate. The motor should be refilled with grease immediately after running for about 2000 hours, and the grease brand must be carefully identified before refilling. When the bearing is found to be overheated or the grease is degraded during operation, it should be replaced in time. The old grease should be removed when replacing, and the bearing and the inner and outer cover oil chambers of the bearing should be cleaned with gasoline, and then clean grease of the same brand should be added. Motor with a speed of 3000rpm and above, the amount of refueling: the bearing cavity is filled, the amount of grease added to the oil chamber of the bearing inner cover accounts for 1/2 of the oil chamber, the remaining speed motor refueling amount: the bearing inner cavity is filled, and the bearing inner cover oil chamber is filled The amount of grease occupies 2/3 of the oil chamber.
2. When replacing the bearing, a special bearing disassembly tool must be used to pull the bearing from the motor shaft, and the disassembly force must not be directly applied to the motor shaft. When installing a new bearing, the hot sleeve method should be used to install the bearing. After the bearing is heated to 90°C, the bearing sleeve should be placed on the bearing position on the shaft.
III. Storage
The motor should be stored in a ventilated and dry place without corrosive gas.
Safety Precautions
1. The lifting ring must be used for lifting during transportation, and the rated load of the spreader must be greater than the weight of the motor, otherwise, it may cause injury to the person and the motor.
2. The motor is forbidden to be used in places with flammable, explosive gas, steam, and corrosive gas.
3. Please install, wire, and debug in strict accordance with the requirements of this manual.
4. Confirm the direction of motor rotation before running.
5. The power supply must be cut off during installation and wiring.
Application of rare earth permanent magnet motor:
Due to the superiority of rare earth permanent magnet motors, their applications are becoming more and more extensive. The main application areas are as follows:
Focus on the high efficiency and energy saving of rare earth permanent magnet motors. The main application objects are large power consumers, such as rare earth permanent magnet synchronous motors for textile and chemical fiber industries, rare earth permanent magnet synchronous motors for various mining and transportation machinery used in oil fields and coal mines, and rare earth permanent magnet synchronous motors for driving various pumps and fans.
