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NdFeB Rare Earth PMAC Motor with Air Cooling and IP54 Protection Grade
What Is The Permanent Magnet Synchronous Motor?
The PERMANENT MAGNET SYNCHRONOUS MOTOR is mainly composed of the stator, rotor, chassis, front-rear cover, bearings, etc. The structure of the stator is basically the same as that of ordinary asynchronous motors, and the main difference between the permanent magnet synchronous motor and other kinds of motors is its rotor.
The permanent magnet material with pre-magnetized (magnetic charged) magnetic on the surface or inside the permanent magnet of the motor, provides the necessary air gap magnetic field for the motor. This rotor structure can effectively reduce the motor volume, reduce loss and improve efficiency.
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.
Due to the use of permanent magnets to provide magnetic fields, the rotor process is mature, reliable, and flexible in size, and the design capacity can be as small as tens of watts, up to megawatts. At the same time, by increasing or decreasing the number of pairs of rotor permanent magnets, it is easier to change the number of poles of the motor, which makes the speed range of permanent magnet synchronous motors wider. With multi-pole permanent magnet rotors, the rated speed can be as low as a single digit, which is difficult to achieve by ordinary asynchronous motors.
Especially in the low-speed high-power application environment, the permanent magnet synchronous motor can be directly driven by a multi-pole design at low speed, compared with an ordinary motor plus reducer, the advantages of a permanent magnet synchronous motor can be highlighted.
Working of Permanent Magnet Synchronous Motor:
The working of the permanent magnet synchronous motor is very simple, fast, and effective when compared to conventional motors. The working of PMSM depends on the rotating magnetic field of the stator and the constant magnetic field of the rotor. The permanent magnets are used as the rotor to create constant magnetic flux and operate and lock at synchronous speed. These types of motors are similar to brushless DC motors.
The phasor groups are formed by joining the windings of the stator with one another. These phasor groups are joined together to form different connections like a star, Delta, and double and single phases. To reduce harmonic voltages, the windings should be wound shortly with each other.
When the 3-phase AC supply is given to the stator, it creates a rotating magnetic field and the constant magnetic field is induced due to the permanent magnet of the rotor. This rotor operates in synchronism with the synchronous speed. The whole working of the PMSM depends on the air gap between the stator and rotor with no load.
If the air gap is large, then the windage losses of the motor will be reduced. The field poles created by the permanent magnet are salient. The permanent magnet synchronous motors are not self-starting motors. So, it is necessary to control the variable frequency of the stator electronically.
What applications use PMSM motors?
Industries that use PMSM motors include Metallurgical, Ceramic, Rubber, Petroleum, Textiles, and many others. PMSM motors can be designed to operate at synchronous speed from a supply of constant voltage and frequency as well as Variable Speed Drive (VSD) applications. Due to high efficiency and power and torque densities, they are generally a superior choice in high torque applications such as mixers, grinders, pumps, fans, blowers, conveyors, and industrial applications where traditionally induction motors are found.
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 the demagnetization phenomenon occurs, which reduces the performance of the permanent magnet motor.
PM motor structures
PM motor structures can be separated into two categories: interior
and surface. Each category has its subset of categories. A surface
PM motor can have its magnets on or inset into the surface of the
rotor, to increase the robustness of the design. An interior
permanent magnet motor positioning and design can vary widely. The
IPM motor’s magnets can be inset as a large block or staggered as
they come closer to the core. Another method is to have them
embedded in a spoke pattern.
PM motor inductance variation with load
Only so much flux can be linked to a piece of iron to generate
torque. Eventually, the iron will saturate and no longer allow flux
to link. The result is a reduction in the inductance of the path
taken by a flux field. In a PM machine, the d-axis and q-axis
inductance values will reduce with increases in the load current.
The d and q-axis inductances of an SPM motor are nearly identical. Because the magnet is outside of the rotor, the inductance of the q-axis will drop at the same rate as the d-axis inductance. However, the inductance of an IPM motor will reduce differently. Again, the d-axis inductance is naturally lower because the magnet is in the flux path and does not generate an inductive property. Therefore, there is less iron to saturate in the d-axis, which results in a significantly lower reduction in flux with respect to the q-axis.
Flux weakening/intensifying of PM motors
Flux in a permanent magnet motor is generated by the magnets. The
flux field follows a certain path, which can be boosted or opposed.
Boosting or intensifying the flux field will allow the motor to
temporarily increase torque production. Opposing the flux field
will negate the existing magnet field of the motor. The reduced
magnet field will limit torque production, but reduce the back-emf
voltage. The reduced back-emf voltage frees up the voltage to push
the motor to operate at higher output speeds. Both types of
operation require additional motor current. The direction of the
motor current across the d-axis, provided by the motor controller,
determines the desired effect.
Structure of the IPM (interior permanent magnet) motor
A conventional SPM (surface permanent magnet) motor has a structure in which a permanent magnet is attached to the rotor surface. It only uses magnetic torque from a magnet. On the other hand, the IPM motor uses reluctance through magnetic resistance in addition to magnetic torque by embedding a permanent magnet in the rotor itself.
SPM.IPM Motor Rotor Structure
IPM (Interior Permanent Magnet) Motor Features
High torque and high efficiency
High torque and high output are achieved by using reluctance torque
in addition to magnetic torque.
Energy-saving operation
It consumes up to 30% less power compared to conventional SPM
motors.
High-speed rotation
It can respond to high-speed motor rotation by controlling the two
types of torque using vector control.
Safety
Since the permanent magnet is embedded, mechanical safety is
improved as, unlike in an SPM, the magnet will not detach due to
centrifugal force.
Vector Control Features
While a conventional system (120-degree conduction system) has the current impressed in the motor as a square wave, a vector control impresses voltage which turns into a sine wave towards the rotor's position (angle of the magnet), so it becomes possible to control the motor current.
Analysis on the Application of Modern Permanent Magnet Motor Technology
1. Application of permanent magnet electromechanical technology to the home appliance market
The application of permanent magnet motor technology to the home appliance market is manifested in VCDDVD and computers. At present, it has gradually formed the development of industrialization and has gradually expanded to multi-phase variable speed drives. For example, people use Inverter air conditioners use modern permanent magnet motor technology to improve the operating efficiency of the air conditioner, gradually reduce the volume of the air conditioner motor, and minimize the noise caused by the air conditioner.
2. Application of permanent magnet electromechanical technology in the elevator market
The permanent magnet motor variable speed system has been used in the elevator market for almost 10 years. For example, by using a low-speed rare earth permanent magnet motor as the elevator traction machine, the use of rare earth permanent magnet motor can save elevator use 20 % of electric energy. Modern permanent magnet motors are usually used in the field of variable-speed drive systems with large load changes and high-speed adjustment requirements.
3. Application of permanent magnet electromechanical technology in industrial and mining enterprises
With the development of permanent magnet motors, large torque permanent magnet motors have been well developed, especially the successful launch of permanent magnet variable frequency motors on the market has given heavy industrial and mining enterprises new choices. Since the output torque of the permanent magnet motor is large enough, the use of the mechanical transmission is reduced and the speed is controllable. It can run at low speeds. Therefore, the application of the fluid coupling is eliminated, which saves the cost of purchasing related equipment and the maintenance of the above two equipment, which reduces the safety risk, so the permanent magnet variable frequency motor is very popular in many industrial and mining enterprises. Because of its variable frequency speed regulation function, it provides a strong guarantee for users to improve production efficiency and save electric energy. Therefore, modern permanent magnet variable frequency motors are a necessary choice for industrial and mining enterprises to upgrade their equipment in the future.
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