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Permanent magnet motors eliminate the need for reactive excitation current, which is required in induction motors. This results in more efficient operation as the motor no longer needs to supply energy to generate a magnetic field.
The elimination of reactive excitation current improves the power factor of permanent magnet motors. This means that the motor can convert more of the input electrical power into mechanical power, leading to higher efficiency.
Without the need for an excitation current, the stator current in permanent magnet motors is significantly reduced. This reduction in current decreases the losses in the stator windings, improving overall motor efficiency.
Permanent magnet motors do not have rotor windings or the associated resistance losses. In induction motors, these losses occur due to the current flowing through the rotor windings, but permanent magnet motors avoid these entirely.
Since permanent magnet motors are more efficient and generate less heat, the need for cooling, such as fans, is reduced. This decreases wind friction losses, further enhancing motor efficiency.
Permanent magnet motors are generally 10 to 15 percentage points more efficient than induction motors of the same specifications. This higher efficiency is due to lower overall losses in the motor design.
Permanent magnet synchronous motors maintain high efficiency and power factor across a wide range of loads, from 25% to 120% of the rated load. This makes them particularly effective during light load operation, where they remain efficient.
Surface-mounted magnets are placed on the rotor’s outer surface. This configuration is simple and cost-effective but can be less efficient at higher speeds due to higher centrifugal forces.
Built-in or interior permanent magnets are embedded within the rotor. This design offers better mechanical integrity and can handle higher speeds more efficiently.
In radial structures, the magnetic flux is directed radially outward from the rotor to the stator. This is a common and straightforward configuration.
Tangential structures direct the magnetic flux tangentially. This allows for a larger excitation area and is particularly suitable for multi-pole motors where high torque is needed.
Hybrid structures combine features of radial and tangential designs to optimize performance for specific applications. These are less common due to their complexity.
A multi-pole structure is used to lower the rated synchronous speed by increasing the number of poles. This helps in achieving high torque at low speeds, which is beneficial for direct drive applications.
For low-speed and high-torque requirements, optimizing the motor design with a sufficient number of poles and appropriate magnet placement is crucial. This ensures efficient performance without excessive inverter currents.
The output frequency of the SPWM inverter should be high (typically above 25 Hz) to ensure a sufficient linear adjustment range for the drive system.
The motor should be designed to have a low rated synchronous speed to match the inverter output, minimizing the need for high inverter currents and reducing overall system costs and losses.
The magnetic field strength provided by the permanent magnets must be sufficient to generate the required torque. This is achieved by optimizing the magnet size and placement.
The tangential structure is particularly suitable for multi-pole motors because it allows for a larger excitation area under each pole, providing strong magnetic fields necessary for high torque output.
When using fractional slot windings, the pole-slot matching is selected so that the number of slots per pole per phase (Q) is less than 1. This configuration helps in optimizing the motor performance.
Fractional slot windings help in reducing the cogging torque amplitude, which minimizes torque pulsations and enhances motor smoothness.
By reducing cogging torque, fractional slot windings improve the speed regulation accuracy, making the motor’s operation more precise.
The smooth operation resulting from fractional slot windings leads to lower vibration and noise levels, contributing to a quieter motor performance.
Fractional slot windings improve the distribution of the winding, which enhances the sinusoidal nature of the motor’s induced back electromotive force (EMF).
A more sinusoidal back EMF results in better overall motor performance, including reduced harmonic distortion and smoother operation.
Using smaller slots in the stator increases the effective utilization area, allowing for more efficient use of the stator material.
The coil end length is shortened in fractional slot windings, reducing the amount of copper needed and minimizing resistive losses.
A motor pitch of 1 means each coil is wound around a single tooth, which simplifies the winding process and enhances motor efficiency.
This design reduces the circumference and extension length of the coil, leading to lower copper losses and improved efficiency.
By minimizing the length of the winding and using less copper, fractional slot windings reduce copper losses, which enhances overall motor efficiency.
The design of fractional slot windings results in cost savings due to less material usage and lower production costs, along with improved motor efficiency.
ENNENG is a leader in the field of Permanent Magnet Direct Drive Motor.
ENNENG specializes in the development and manufacturing of Permanent Magnet Direct Drive Motors. These motors are designed with a permanent magnet rotor and are widely used in various industries such as gold mines, coal mines, tire factories, oil wells, and water treatment plants. The Permanent Magnet Direct Drive Motors offer several advantages over traditional motor systems. They eliminate the need for a reducer, resulting in low mechanical noise, small vibration, and a low failure rate. The motors have a high efficiency of up to 93-97% and a power factor of up to 0.99, leading to energy savings and increased active power in the system. Compared to motors with speed reducers, the Permanent Magnet Direct Drive Motors have higher transmission efficiency and require less maintenance. With their compact design and reliable performance, these motors are an ideal choice for applications that require low speed and high power.
