5.5-3000KW 380V 660V Permanent Magnet Gearless Motor High Torque High Output

Working Principle

The permanent magnet synchronous motor working principle is similar to the synchronous motor. It depends on the rotating magnetic field that generates electromotive force at synchronous speed. When the stator winding is energized by giving the 3-phase supply, a rotating magnetic field is created in between the air gaps.

This produces the torque when the rotor field poles hold the rotating magnetic field at synchronous speed and the rotor rotates continuously. As these motors are not self-starting motors, it is necessary to provide a variable frequency power supply.

EMF and Torque Equation

In a synchronous machine, the average EMF induced per phase is called dynamic induces EMF in a synchronous motor, the flux cut by each conductor per revolution is Pϕ Weber

Then the time taken to complete one revolution is 60/N sec

The average EMF induced per conductor can be calculated by using

( PϕN / 60 ) x Zph = ( PϕN / 60 ) x 2Tph

Where Tph = Zph / 2

Therefore, the average EMF per phase is,

= 4 x ϕ x Tph x PN/120 = 4ϕfTph

Where Tph = no. Of turns connected in series per phase

ϕ = flux/pole in weber

P= no. Of poles

F= frequency in Hz

Zph= no. Of conductors connected in series per phase. = Zph/3

The EMF equation depends on the coils and the conductors on the stator. For this motor, the distribution factor Kd and pitch factor Kp are also considered.

Hence, E = 4 x ϕ x f x Tph xKd x Kp

The torque equation of a permanent magnet synchronous motor is given as,

T = (3 x Eph x Iph x sinβ) / ωm

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.

Self-sensing versus closed-loop operation

Recent advances in drive technology allow standard ac drives to “self-detect” and track the motor magnet position. A closed-loop system typically uses the z-pulse channel to optimize performance. Through certain routines, the drive knows the exact position of the motor magnet by tracking the A/B channels and correcting for errors with the z-channel. Knowing the exact position of the magnet allows for optimum torque production resulting in optimum efficiency.

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.

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.