The document discusses several types of permanent magnet (PM) motors, including brushed DC motors, brushless DC motors, AC synchronous motors, PM stepper motors, switched reluctance motors, and linear PM motors. It notes the advantages and applications of each type. The document then focuses on brushless DC (BLDC) motors and permanent magnet synchronous motors (PMSM), comparing their drive configurations, which involve using an inverter and electronic commutation to control motor speed and torque based on position sensor feedback. It also discusses speed and torque control methods for BLDC and PMSM motors.

1. Permanent magnet motor
drives
Suvendu Mondal
EE, AP, SurTech

2. Introduction to various PM motors
• There are several types of PM (permanent magnet) motors, each with their own unique characteristics and advantages. Here are brief introductions to some of the most
common types:
• 1. Brushed DC Motors: Brushed DC motors use a PM to generate a magnetic field and a commutator to switch the direction of the current flowing through the motor windings.
They are simple, reliable, and low-cost, but have low efficiency and are prone to wear and tear due to the brushes.
• 2. Brushless DC Motors: Brushless DC motors use a PM rotor and an electronic commutation system to control the speed and direction of the motor. They offer high efficiency,
low maintenance, and long life, but are more complex and expensive than brushed DC motors.
• 3. AC Synchronous Motors: AC synchronous motors use a PM rotor and a stator with alternating magnetic fields to generate torque. They offer high efficiency and precise
speed control, but require a specialized control system and are more expensive than other types of motors.
• 4. PM stepper motors: PM stepper motors use a PM rotor and a stator with multiple poles to generate precise, incremental movements. They offer high precision and excellent
holding torque, but can be noisy and have limited speed ranges.
• 5. Switched Reluctance Motors: Switched reluctance motors use a rotor with salient poles and a stator with concentrated windings to generate torque. They offer high
efficiency, low cost, and robustness, but have limited speed ranges and can be noisy.
• 6. Linear PM Motors: Linear PM motors use a PM to generate a linear motion instead of a rotary motion. They offer high precision and efficiency, but can be more complex and
expensive than other types of motors.
• Overall, PM motors offer several advantages over other types of motors, including high efficiency, low maintenance, and high precision. The specific type of PM motor chosen
will depend on the specific application requirements and constraints.

3. BLDC and PMSM drive configuration
• BLDC (Brushless DC) and PMSM (Permanent Magnet Synchronous Motor) are two types of PM motor drives that use electronic commutation to control the motor speed and torque. Here are some common
drive configurations for these motors:
• BLDC Drive Configuration:
• - Power Supply: A DC voltage source is used to power the drive.
• - Inverter: A three-phase inverter is used to convert the DC voltage into three-phase AC voltage.
• - Commutation: Electronic commutation is used to switch the inverter output to the correct phase winding based on the position of the rotor.
• - Control System: A microcontroller or digital signal processor (DSP) is used to control the inverter and commutation based on feedback from position sensors such as Hall-effect sensors.
• PMSM Drive Configuration:
• - Power Supply: A three-phase AC voltage source is used to power the drive.
• - Inverter: A three-phase inverter is used to control the voltage and frequency of the AC voltage applied to the motor.
• - Commutation: Electronic commutation is used to synchronize the inverter output with the position of the rotor based on feedback from position sensors such as encoders or resolvers.
• - Control System: A microcontroller or DSP is used to control the inverter and commutation based on feedback from the position sensors and other sensors such as current sensors.
• The main difference between the two drive configurations is the type of power supply used. BLDC motors require a DC voltage source, while PMSM motors require a three-phase AC voltage source. The
control system for both types of drives is similar, with electronic commutation used to control the motor speed and torque based on feedback from position sensors.
• Overall, both BLDC and PMSM drives offer high efficiency, low maintenance, and precise control over motor speed and torque. The specific type of drive chosen will depend on the specific application
requirements and constraints.

4. Difference between BLDC and PMMC
• Differences:
1. Power Supply: BLDC motors require a DC voltage source, while PMDC
motors can operate with either a DC or AC voltage source.
2. Commutation: BLDC motors use trapezoidal or sinusoidal commutation,
while PMDC motors use mechanical commutation with a commutator
and brushes.
3. Speed Range: BLDC motors have a wider speed range and better
controllability than PMDC motors, which have a limited speed range due
to mechanical commutation.
4. Torque Ripple: BLDC motors have lower torque ripple than PMDC
motors, which can cause speed fluctuations and vibration in the system.
5. Cost: BLDC motors are generally more expensive than PMDC motors due
to the complexity of the electronic commutation system.

5. Block diagrams of BLDC

6. Block Diagram of PMMC

7. Speed and torque control in BLDC and PMSM
• Speed and torque control in BLDC (Brushless DC) and PMSM (Permanent Magnet Synchronous Motor) are typically achieved
using a closed-loop control system that adjusts the motor input voltage and current to achieve the desired speed and torque.
• In both BLDC and PMSM, the speed and torque can be controlled using two main control strategies:
• 1. Scalar Control: This is a simple and commonly used method of controlling the motor speed and torque. In scalar control, the
amplitude of the motor input voltage or current is adjusted to control the motor speed and torque. The control system
typically uses a PI (Proportional-Integral) controller to adjust the voltage or current based on feedback from the speed and
current sensors. Scalar control can provide good performance for low-speed applications, but it may have limitations at high
speeds or in dynamic applications.
• 2. Vector Control (also known as Field-Oriented Control or FOC): This is a more advanced control method that allows for more
precise control of the motor speed and torque. In vector control, the motor input voltage and current are represented as two
orthogonal components, one that generates magnetic flux and one that generates torque. The control system adjusts these
components independently to achieve the desired speed and torque. Vector control requires more complex control algorithms
and signal processing, but it can provide high-performance control for a wide range of operating conditions.
• Overall, both BLDC and PMSM can be controlled using scalar or vector control, depending on the specific requirements of the
application. Scalar control is simpler and less expensive, but vector control can provide higher performance and better control
for dynamic and high-speed applications.