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.

Working of Permanent Magnet Synchronous Motor:

The working of the permanent magnet synchronous motor is very simple, fast, and effective when compared to conventional motors. The working of PMSM depends on the rotating magnetic field of the stator and the constant magnetic field of the rotor. The permanent magnets are used as the rotor to create constant magnetic flux and operate and lock at synchronous speed. These types of motors are similar to brushless DC motors.

The phasor groups are formed by joining the windings of the stator with one another. These phasor groups are joined together to form different connections like a star, Delta, and double and single phases. To reduce harmonic voltages, the windings should be wound shortly with each other.

When the 3-phase AC supply is given to the stator, it creates a rotating magnetic field and the constant magnetic field is induced due to the permanent magnet of the rotor. This rotor operates in synchronism with the synchronous speed. The whole working of the PMSM depends on the air gap between the stator and rotor with no load.

If the air gap is large, then the windage losses of the motor will be reduced. The field poles created by the permanent magnet are salient. The permanent magnet synchronous motors are not self-starting motors. So, it is necessary to control the variable frequency of the stator electronically.

Structure of the IPM (interior permanent magnet) motor

The permanent magnet synchronous motors, like any rotating electric motor, consist of a rotor and a stator. The permanent magnet synchronous motor construction is similar to the basic synchronous motor, but the only difference is with the rotor. In this type of motor, the permanent magnets are mounted on the rotor and the rotor doesn’t have any field winding.

The permanent magnets are used to create field poles. The permanent magnets used in the PMSM are made up of samarium-cobalt and medium, iron, and boron because of their higher permeability. The most widely used permanent magnet is neodymium-boron-iron because of its effective cost and ease of availability.

SPM vs IPM Motor Rotor Structure

IPM (Interior Permanent Magnet) Motor Features

High torque and high efficiency
High torque and high output are achieved by using reluctance torque in addition to magnetic torque.

Energy-saving operation
It consumes up to 30% less power compared to conventional SPM motors.

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

Safety
Since the permanent magnet is embedded, mechanical safety is improved as, unlike in an SPM, the magnet will not detach due to centrifugal force.

Vector Control Features

While a conventional system (120-degree conduction system) has the current impressed in the motor as a square wave, a vector control impresses voltage which turns into a sine wave towards the rotor's position (angle of the magnet), so it becomes possible to control the motor current.

The permanent magnetic synchronous motor has the following characteristics:

• No sparks, safer in explosive environments
• Clean, fast, and efficient
• More compact, efficient, and lighter than an ACIM
• Designed for high-performance servo applications
• Runs with/without position encoders
• Low audible noise and EMI
• Smooth low and high speed performance
• Produces optimal torque when coupled with Field-Oriented Control (FOC)