4 Poles Gearless Permanent Magnet Motor China Manufacturer

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.

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.

Permanent magnet AC (PMAC) motors have a wide range of applications including:

Industrial Machinery: PMAC motors are used in a variety of industrial machinery applications, such as pumps, compressors, fans, and machine tools. They offer high efficiency, high power density, and precise control, making them ideal for these applications.

Robotics: PMAC motors are used in robotics and automation applications, where they offer high torque density, precise control, and high efficiency. They are often used in robotic arms, grippers, and other motion control systems.

HVAC Systems: PMAC motors are used in heating, ventilation, and air conditioning (HVAC) systems, where they offer high efficiency, precise control, and low noise levels. They are often used in fans and pumps in these systems.

Renewable Energy Systems: PMAC motors are used in renewable energy systems, such as wind turbines and solar trackers, where they offer high efficiency, high power density, and precise control. They are often used in the generators and tracking systems in these systems.

Medical Equipment: PMAC motors are used in medical equipment, such as MRI machines, where they offer high torque density, precise control, and low noise levels. They are often used in the motors that drive the moving parts in these machines.

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.

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.

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.