Variable Speed Permanent Magnet AC Motor For Mixing Tank

In the general industrial sector, the replacement of low-voltage(380/660/1140V) high-efficiency asynchronous motors, the system saves 5% to 30% energy, and the high-voltage(6kV/10kV) high-efficiency asynchronous motors, the system saves 2% to10%.

Advantages of permanent magnet motors:

1. Higher Efficiency: Permanent magnet motors are known for their high efficiency. The use of permanent magnets eliminates the need for a separate excitation coil, reducing energy losses associated with excitation. This results in improved efficiency and reduced energy consumption, making permanent magnet motors more energy-efficient than other motor types.

2. High Power Density: Permanent magnet motors have a high power density, meaning they can deliver a high amount of torque relative to their size and weight. This makes them ideal for applications where space and weight are limited, such as in electric vehicles or small-scale machinery.

3. Compact and Lightweight: The absence of an excitation coil and the use of permanent magnets contribute to the compact and lightweight design of permanent magnet motors. This makes them easier to integrate into various systems and reduces the overall weight of the application.

4. Improved Dynamic Response: Permanent magnet motors typically have a faster dynamic response compared to other motor types. They can quickly accelerate, decelerate, and change direction, making them suitable for applications that require precise and rapid control of motor speed and position.

5. Reduced Maintenance: Permanent magnet motors have fewer parts compared to other motor types, resulting in reduced maintenance requirements. Since there are no brushes or commutators, there is no need for regular brush replacement or commutator maintenance. This leads to lower maintenance costs and increased reliability.

6. Wide Speed Range: Permanent magnet motors can operate over a wide range of speeds, from low to high speeds, without sacrificing efficiency or performance. This versatility makes them suitable for a variety of applications, including both low-speed and high-speed machinery.

It's important to note that the specific advantages of permanent magnet motors can vary depending on the application and the specific design and configuration of the motor. However, in general, their high efficiency, compactness, power density, and low maintenance requirements make them a preferred choice in many industrial, commercial, and automotive applications.

Application:

Permanent magnet synchronous motors can be combined with frequency converters to form the best open-loop step-less speed control system, which has been widely used for speed control transmission equipment in petrochemical, chemical fiber, textile, machinery, electronics, glass, rubber, packaging, printing, paper making, printing and dyeing, metallurgy and other industries.

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 one. 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 has the ability to generate torque by taking advantage of both the magnetic and reluctance torque components of the motor.

Why you should choose an IPM motor instead of an SPM?

1. High torque is achieved by using reluctance torque in addition to magnetic torque.

2. IPM motors consume up to 30% less power compared to conventional electric motors.

3. Mechanical safety is improved as, unlike in an SPM, the magnet will not detach due to centrifugal force.

4. It can respond to high-speed motor rotation by controlling the two types of torque using vector control.

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 maybe 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.

How to improve the efficiency of the motor?

To improve the efficiency of the motor, the essence is to reduce the loss of the motor. The loss of the motor is divided into mechanical loss and electromagnetic loss. For example, for an AC asynchronous motor, the current passes through the stator and rotor windings, which will produce copper loss and conductor loss, while the magnetic field is in the iron. It will cause eddy currents to bring about hysteresis loss, high harmonics of the air magnetic field will generate stray losses on the load, and there will be wear losses during the rotation of bearings and fans.

To reduce the loss of the rotor, you can reduce the resistance of the rotor winding, use a relatively thick wire with low resistivity, or increase the cross-sectional area of the rotor slot. Of course, the material is very important. Conditional production of copper rotors will reduce losses by about 15%. The current asynchronous motors are basically aluminum rotors, so the efficiency is not so high.

Similarly, there is copper loss on the stator, which can increase the slot face of the stator, increase the full slot ratio of the stator slot, and shorten the end length of the stator winding. If a permanent magnet is used to replace the stator winding, there is no need to pass the current. Of course, the efficiency can be obviously improved, which is the fundamental reason why the synchronous motor is more efficient than the asynchronous motor.

For the iron loss of the motor, high-quality silicon steel sheets can be used to reduce the loss of the hysteresis or the length of the iron core can be lengthened, which can reduce the magnetic flux density, and can also increase the insulating coating. In addition, the heat treatment process is also critical.

The ventilation performance of the motor is more important. When the temperature is high, the loss will of course be large. The corresponding cooling structure or additional cooling method can be used to reduce friction loss.

High-order harmonics will produce stray losses in the winding and iron core, which can improve the stator winding and reduce the generation of high-order harmonics. Insulation treatment can also be performed on the surface of the rotor slot, and magnetic slot mud can be used to reduce the magnetic slot effect.

Due to the need for a drive or controller, variable-speed PMAC motors cost much more than constant-speed Premium Efficiency induction motors. PM motors have variable-speed capability, however, so are equivalent replacements for an electronic pulse-width modulated variable frequency drive (VFD) controlling a new Premium Efficiency inverter-duty motor. When replacing constant-speed motors in variable flow applications, energy savings due to the variable-speed capability of the PMAC motor will greatly exceed the savings due to the increased efficiency of the motor itself. Permanent magnet motors provide improved efficiency over their entire operating range and meet or exceed the International Electrotechnical Commission (IEC) IE4 efficiency standards.