High Power Industry Use Energy Saving IPM SPM Motor

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.

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.

Advantages:

Small And Lightweight

In special electromagnetic and structural design, the volume-to-weight ratio is reduced by 20%, the length of the whole machine is reduced by 10%, and the full rate of stator slots is increased to 90%.

Highly Integrated

The motor and the inverter are highly integrated, avoiding the external circuit connection between the motor and the inverter, and improving the reliability of the system products.

Energy Efficient

High-performance rare-earth permanent magnet material, special stator slot, and rotor structure make this motor efficient up to IE4 standard.

Custom Design

Customized design and manufacture, dedicated to special machines, reduce redundant functions and design margins and minimize costs.

Low Vibration And Noise

The motor is directly driven, the equipment noise and vibration are small, and the impact on the construction work environment is reduced.

Maintenance Free

No high-speed gear parts, no need to change gear lubricant regularly, and truly maintenance-free equipment.

IPM VS SPM

A permanent magnet motor (also called PM) can be separated into two main categories: Interior Permanent Magnet (IPM) and Surface Permanent Magnet (SPM). Both types generate magnetic flux by the permanent magnets affixed to or inside of the rotor.

SPM

SURFACE PERMANENT MAGNET

A type of motor in which permanent magnets are attached to the rotor circumference.

SPM motors have magnets affixed to the exterior of the rotor surface, their mechanical strength is so weaker than the IPM ones. 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

INTERIOR PERMANENT MAGNET

A type of motor that has a rotor embedded with permanent magnets is called IPM.

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 can generate torque by taking advantage of both the magnetic and reluctance torque components of the motor.

What is the energy-saving effect of a low-speed high-power permanent magnet direct drive motor? We refer to the energy-saving effect test data released by the Energy Saving Monitoring Center, as follows:

At present, because low-speed permanent magnet synchronous motors have the advantages of low speed and high torque, smaller volume than motors + reducers of the same power, stable output, high efficiency, and energy saving, they are used as driving devices in many fields, such as mining, coal, cement, Belt conveyors, scrapers, bucket wheel machines, ball mills, hoisting machinery, open mills, internal mixers, extruders, vacuum pumps, reciprocating compressors, Low-speed pumps with low head and large flow, etc. used in the fields of metallurgy, petroleum, chemical industry, and water conservancy engineering. As we all know, mining, coal, cement, metallurgy, petroleum, chemical industry, etc. are industries with high energy consumption and high pollution. Currently, heavy machinery equipment such as belt conveyors, elevators, and ball mills mainly use induction motors, reducers, and the transmission mode of large and small open gears and the penetration rate of low-speed and high-torque permanent magnet motors is low. As the Chinese government continues to transform and upgrade the above-mentioned industries and the energy-saving transformation requirements continue to increase, the demand for low-speed and high-torque permanent magnet motors in these industries may increase. The market size of low-speed and high-torque permanent magnet motors will show a steady growth trend.