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.
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.
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
Advantages
The advantages of the permanent magnet synchronous motor include:
Provides higher efficiency at high speeds
Available in small sizes in different packages
Maintenance and installation are very easy than with an induction motor
Capable of maintaining full torque at low speeds
High efficiency and reliability
Gives smooth torque and dynamic performance
Disadvantages
The disadvantages of permanent magnet synchronous motors are:
These types of motors are very expensive when compared to induction motors
Somehow difficult to start up because they are not self-starting motors.
