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[China]
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Address: No. 18, Xinye Road, High-Tech Zone, Qingdao,Shandong, China
Contact name:Cindy
QINGDAO ENNENG MOTOR CO.,LTD. |
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Verified Suppliers
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High Starting Torque And Overload Capacity Neodymium Magnet Motor
Frequency | 50Hz |
High Power factor | Almost 1 |
Large Starting Torgue | 2 times more than others |
Range of frequency | > 1:1000 |
Working Mode | S1 |
Cooling Mode | IC411 |
Enclosure Protection Grade | IP54 |
Advantage | Small, light, high efficiency, low noise, etc |
What Is The Permanent Magnet Synchronous Motor?
A PM motor is an ac motor that uses magnets embedded into or attached to the surface of the motor’s rotor. The magnets are used to generate a constant motor flux instead of requiring the stator field to generate one by linking to the rotor, as is the case with an induction 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.
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.
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.
Back-emf waveform
Back emf is short for back electromotive force but is also known as the counter-electromotive force. The back electromotive force is the voltage that occurs in electric motors when there is a relative motion between the stator windings and the rotor’s magnetic field. The geometric properties of the rotor will determine the shape of the back-emf waveform. These waveforms can be sinusoidal, trapezoidal, triangular, or something in between.
Both induction and PM machines generate back-emf waveforms. In an induction machine, the back-emf waveform will decay as the residual rotor field slowly decays because of the lack of a stator field. However, with a PM machine, the rotor generates its own magnetic field. Therefore, a voltage can be induced in the stator windings whenever the rotor is in motion. Back-emf voltage will rise linearly with speed and is a crucial factor in determining maximum operating speed.
Why choose permanent magnet ac motors?
Permanent magnet AC (PMAC) motors offer several advantages over other types of motors, including:
High Efficiency: PMAC motors are highly efficient due to the absence of rotor copper losses and reduced winding losses. They can achieve efficiencies of up to 97%, resulting in significant energy savings.
High Power Density: PMAC motors have a higher power density compared to other motor types, which means they can produce more power per unit of size and weight. This makes them ideal for applications where space is limited.
High Torque Density: PMAC motors have a high torque density, which means they can produce more torque per unit of size and weight. This makes them ideal for applications where high torque is required.
Reduced Maintenance: Since PMAC motors have no brushes, they require less maintenance and have a longer lifespan than other motor types.
Improved Control: PMAC motors have better speed and torque control compared to other motor types, making them ideal for applications where precise control is required.
Environmentally Friendly: PMAC motors are more environmentally friendly than other motor types since they use rare earth metals, which are easier to recycle and produce less waste compared to other motor types.
Overall, the advantages of PMAC motors make them an excellent choice for a wide range of applications, including electric vehicles, industrial machinery, and renewable energy systems.
SPM versus IPM
A PM motor can be separated into two main categories: surface permanent magnet motors (SPM) and interior permanent magnet motors (IPM). Neither motor design type contains rotor bars. Both types generate magnetic flux by the permanent magnets affixed to or inside of the rotor.
SPM motors have magnets affixed to the exterior of the rotor surface. Because of this mechanical mounting, their mechanical strength is weaker than that of IPM motors. The weakened mechanical strength limits the motor’s maximum safe mechanical speed. In addition, these motors exhibit very limited magnetic saliency (Ld ≈ Lq). Inductance values measured at the rotor terminals are consistent regardless of the rotor position. Because of the near unity saliency ratio, SPM motor designs rely significantly, if not completely, on the magnetic torque component to produce torque.
IPM motors have a permanent magnet embedded into the rotor itself. Unlike their SPM counterparts, the location of the permanent magnets makes IPM motors very mechanically sound, and suitable for operating at very high speeds. These motors also are defined by their relatively high magnetic saliency ratio (Lq > Ld). Due to their magnetic saliency, an IPM motor has the ability to generate torque by taking advantage of both the magnetic and reluctance torque components of the motor.
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.
Brushless permanent magnet (PM) motors operate with an AC power supply so are often referred to as PMAC motors. The use of permanent magnets eliminates the need for conductors (rotor bars) so rotor losses are eliminated. This design makes it possible to combine high efficiency, low speed, and high torque in a single package. For small motor sizes, the efficiency of the PM motor may be 10% to 15% greater than older, standard-efficiency motors at the same load point. These efficiency gains hold over the entire range of typical motor loads.
Permanent magnet demagnetization
Permanent magnets are hardly permanent and do have limited capabilities. Certain forces can be exerted onto these materials to demagnetize them. In other words, it is possible to remove the magnetic properties of the permanent magnet material. A permanent magnetic substance can become demagnetized if the material is significantly strained, allowed to reach significant temperatures, or is impacted by a large electrical disturbance.
First, straining a permanent magnet is typically done by physical means. A magnetic material can become demagnetized, if not weakened, if it was to experience violent impacts/falls. A ferromagnetic material has inherent magnetic property. However, these magnetic properties can emit in any multitude of directions. One way ferromagnetic materials are magnetized is by applying a strong magnetic field to the material to align its magnetic dipoles. Aligning these dipoles forces the magnetic field of the material into a specific bath. A violent impact can remove the atomic alignment of the material’s magnetic domains, which weakens the strength of the intended magnetic field.
Secondly, temperatures also can affect a permanent magnet. Temperatures force the magnetic particles in a permanent magnet to become agitated. The magnetic dipoles have the ability to withstand some amount of thermal agitation. However, long periods of agitation can weaken a magnet’s strength, even if stored at room temperature. In addition, all magnetic materials have a threshold known as the “Curie temperature,” which is a threshold that defines the temperature at which the thermal agitation causes the material to completely demagnetize. Terms such as coercivity and retentivity are used to define magnetic material strength retention capability.
Finally, large electrical disturbances can cause a permanent magnet to demagnetize. These electrical disturbances can be from the material interacting with a large magnetic field or if a large current is passed through the material. Much in the same way a strong magnetic field or current can be used to align a material’s magnetic dipoles, another strong magnetic field or current applied to the field generated by the permanent magnet can result in demagnetization.
