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How to choose a motor in industrial automation
Add Date:2024/7/26 Views:104
Understanding the major types of loads, motors and applications can help simplify the selection of industrial motors and accessories. There are many aspects to consider when selecting an industrial motor, such as application, operational, mechanical and environmental issues. In general, you can choose from AC motors, DC motors or servo/stepper motors. Knowing which one to use depends on the industrial application and if there are any special needs. Depending on the type of load the motor is driving, industrial motors require a constant or variable torque and horsepower. The size of the load, the required speed and acceleration/deceleration - especially if it is fast and/or frequent - will determine the torque and horsepower required. Consideration also needs to be given to the requirements for controlling motor speed and position.
There are four types of industrial automation motor loads.
1, Adjustable Horsepower and Constant Torque: Variable horsepower and constant torque applications include conveyors, cranes and geared pumps. In these applications, the torque is constant because the load is constant. The horsepower required may vary depending on the application, making constant speed AC and DC motors a good choice.
2. Variable Torque and Constant Horsepower: An example of a variable torque and constant horsepower application is a machine rewinding paper. The speed of the material remains constant, which means that the horsepower does not change. However, as the roll diameter increases, the load changes. In small systems, this is a good application for DC motors or servo motors. Regenerative power is also a concern and should be considered when sizing industrial motors or selecting energy control methods. AC motors with encoders, closed-loop control, and full-quadrant drives may benefit larger systems.
3. Adjustable horsepower and torque: Fans, centrifugal pumps, and agitators require variable horsepower and torque. As the speed of an industrial motor increases, the load output increases with the required horsepower and torque. These types of loads are the beginning of the motor efficiency discussion, inverter loaded AC motors use variable speed drives (VSDs).
4. Position control or torque control: Applications like linear drives, which need to move accurately to multiple positions, require tight position or torque control, and often require feedback to verify the correct motor position. Servo or stepper motors are the best choice for these applications, but DC motors with feedback or inverter-loaded AC motors with encoders are often used in steel or paper production lines and similar applications.
While there are over 36 types of AC/DC motors used in industrial applications. While there are many types of motors, there is a great deal of overlap in industrial applications and the market has pushed to simplify motor selection. This has narrowed down the actual choice of motors in most applications. The six most common motor types, suitable for the vast majority of applications, are brushless and brushed DC motors, AC squirrel cage and wound rotor motors, servo and stepper motors. These motor types are suitable for the vast majority of applications, while the other types are used only for specialised applications.
Three Main Types of Industrial Motor Applications
The three main applications for industrial motors are constant speed, variable speed and position (or torque) control. Different industrial automation situations require different applications and problems as well as their own problem sets. For example, if the top speed is less than the motor's reference speed, a gearbox is required. This could also allow a smaller motor to run at a more efficient speed. While there is a wealth of information available online on how to size a motor, the user must consider many factors as there are many details to take into account. Calculating load inertia, torque, and speed requires the user to understand parameters such as total mass and size (radius) of the load, as well as friction, gearbox losses, and machine cycles. Load variations, speed of acceleration or deceleration, and duty cycle of the application must also be considered or the industrial motor may overheat. AC induction motors are a popular choice for industrial rotary motion applications. After motor type selection and sizing, users also need to consider environmental factors and motor enclosure types such as open frame and stainless steel enclosures for washing applications.
Three key questions for industrial motor sizing
1. constant speed applications?
In constant speed applications, motors typically run at approximate speeds with little or no consideration of acceleration and deceleration ramps. This type of application is usually run using a full line on/off control. The control circuit usually consists of a branch circuit fuse with a contactor, an overload industrial motor starter, and a manual motor controller or soft starter. Both AC and DC motors are suitable for constant speed applications. DC motors provide full torque at zero speed and have a large mounting base. AC motors are also a good choice because they have a high power factor and require little maintenance. In contrast, the high performance characteristics of servo or stepper motors would be considered excessive for a simple application.
2. variable speed applications?
Variable speed applications typically require tight speed and velocity changes, as well as defined acceleration and deceleration ramps. In practice, reducing the speed of industrial motors, such as fans and centrifugal pumps, is often done by matching the power consumption to the load to improve efficiency rather than running at full speed and throttling or suppressing the output. These are very important considerations for conveying applications such as bottling lines. AC motor and VFD combinations are widely used to improve efficiency and work well in a variety of variable speed applications. Both AC and DC motors with appropriate drives work well in variable speed applications. For a long time, DC motors and drive configurations have been the only choice for variable speed motors, and their components have been developed and proven. Even now, DC motors are popular in variable-speed, fractional-horsepower applications and are useful in low-speed applications because they can provide full torque at low speeds and constant torque at a variety of industrial motor speeds. However, maintenance of DC motors is an issue to consider, as many require brushes for commutation and can wear out due to contact with moving parts. Brushless DC motors eliminate this problem, but they are more expensive upfront and the range of available industrial motors is smaller. Brush wear is not a problem with AC induction motors, and variable frequency drives (VFDs) offer a useful option for applications over 1 hp (such as fans and pumping) that can improve efficiency. Choosing a drive type to run an industrial motor can add some positional awareness. Encoders can be added to the motor if the application requires it, and the drive can be specified to use encoder feedback. As a result, this setup can provide servo-like speeds.
3. Is position control required?
Tight position control is achieved by constantly verifying the position of the motor as it moves. Applications such as positioning linear drives can use stepper motors with or without feedback or servo motors with intrinsic feedback. The stepper moves precisely to a position at a moderate speed and then holds that position. Open-loop stepper systems provide strong position control if properly sized. When there is no feedback, the stepper will move an exact number of steps unless it encounters a load interruption that exceeds its capacity. As the speed and dynamics of an application increase, open-loop stepper control may not meet the requirements of the system, requiring an upgrade to a stepper or servo motor system with feedback. A closed-loop system provides precise, high-speed motion profiling and accurate position control. Servo systems provide higher torque at high speeds than steppers and also work better with highly dynamic loads or complex motion applications. For high-performance motion with low position overshoot, the reflected load inertia should match the servo motor inertia as closely as possible. In some applications, up to a 10:1 mismatch is sufficient, but a 1:1 match is optimal. Gear reduction is a good solution to the inertia mismatch problem because the inertia of the reflected load decreases by the square of the ratio, but the inertia of the gearbox must be taken into account in the calculations.
There are four types of industrial automation motor loads.
1, Adjustable Horsepower and Constant Torque: Variable horsepower and constant torque applications include conveyors, cranes and geared pumps. In these applications, the torque is constant because the load is constant. The horsepower required may vary depending on the application, making constant speed AC and DC motors a good choice.
2. Variable Torque and Constant Horsepower: An example of a variable torque and constant horsepower application is a machine rewinding paper. The speed of the material remains constant, which means that the horsepower does not change. However, as the roll diameter increases, the load changes. In small systems, this is a good application for DC motors or servo motors. Regenerative power is also a concern and should be considered when sizing industrial motors or selecting energy control methods. AC motors with encoders, closed-loop control, and full-quadrant drives may benefit larger systems.
3. Adjustable horsepower and torque: Fans, centrifugal pumps, and agitators require variable horsepower and torque. As the speed of an industrial motor increases, the load output increases with the required horsepower and torque. These types of loads are the beginning of the motor efficiency discussion, inverter loaded AC motors use variable speed drives (VSDs).
4. Position control or torque control: Applications like linear drives, which need to move accurately to multiple positions, require tight position or torque control, and often require feedback to verify the correct motor position. Servo or stepper motors are the best choice for these applications, but DC motors with feedback or inverter-loaded AC motors with encoders are often used in steel or paper production lines and similar applications.
While there are over 36 types of AC/DC motors used in industrial applications. While there are many types of motors, there is a great deal of overlap in industrial applications and the market has pushed to simplify motor selection. This has narrowed down the actual choice of motors in most applications. The six most common motor types, suitable for the vast majority of applications, are brushless and brushed DC motors, AC squirrel cage and wound rotor motors, servo and stepper motors. These motor types are suitable for the vast majority of applications, while the other types are used only for specialised applications.
Three Main Types of Industrial Motor Applications
The three main applications for industrial motors are constant speed, variable speed and position (or torque) control. Different industrial automation situations require different applications and problems as well as their own problem sets. For example, if the top speed is less than the motor's reference speed, a gearbox is required. This could also allow a smaller motor to run at a more efficient speed. While there is a wealth of information available online on how to size a motor, the user must consider many factors as there are many details to take into account. Calculating load inertia, torque, and speed requires the user to understand parameters such as total mass and size (radius) of the load, as well as friction, gearbox losses, and machine cycles. Load variations, speed of acceleration or deceleration, and duty cycle of the application must also be considered or the industrial motor may overheat. AC induction motors are a popular choice for industrial rotary motion applications. After motor type selection and sizing, users also need to consider environmental factors and motor enclosure types such as open frame and stainless steel enclosures for washing applications.
Three key questions for industrial motor sizing
1. constant speed applications?
In constant speed applications, motors typically run at approximate speeds with little or no consideration of acceleration and deceleration ramps. This type of application is usually run using a full line on/off control. The control circuit usually consists of a branch circuit fuse with a contactor, an overload industrial motor starter, and a manual motor controller or soft starter. Both AC and DC motors are suitable for constant speed applications. DC motors provide full torque at zero speed and have a large mounting base. AC motors are also a good choice because they have a high power factor and require little maintenance. In contrast, the high performance characteristics of servo or stepper motors would be considered excessive for a simple application.
2. variable speed applications?
Variable speed applications typically require tight speed and velocity changes, as well as defined acceleration and deceleration ramps. In practice, reducing the speed of industrial motors, such as fans and centrifugal pumps, is often done by matching the power consumption to the load to improve efficiency rather than running at full speed and throttling or suppressing the output. These are very important considerations for conveying applications such as bottling lines. AC motor and VFD combinations are widely used to improve efficiency and work well in a variety of variable speed applications. Both AC and DC motors with appropriate drives work well in variable speed applications. For a long time, DC motors and drive configurations have been the only choice for variable speed motors, and their components have been developed and proven. Even now, DC motors are popular in variable-speed, fractional-horsepower applications and are useful in low-speed applications because they can provide full torque at low speeds and constant torque at a variety of industrial motor speeds. However, maintenance of DC motors is an issue to consider, as many require brushes for commutation and can wear out due to contact with moving parts. Brushless DC motors eliminate this problem, but they are more expensive upfront and the range of available industrial motors is smaller. Brush wear is not a problem with AC induction motors, and variable frequency drives (VFDs) offer a useful option for applications over 1 hp (such as fans and pumping) that can improve efficiency. Choosing a drive type to run an industrial motor can add some positional awareness. Encoders can be added to the motor if the application requires it, and the drive can be specified to use encoder feedback. As a result, this setup can provide servo-like speeds.
3. Is position control required?
Tight position control is achieved by constantly verifying the position of the motor as it moves. Applications such as positioning linear drives can use stepper motors with or without feedback or servo motors with intrinsic feedback. The stepper moves precisely to a position at a moderate speed and then holds that position. Open-loop stepper systems provide strong position control if properly sized. When there is no feedback, the stepper will move an exact number of steps unless it encounters a load interruption that exceeds its capacity. As the speed and dynamics of an application increase, open-loop stepper control may not meet the requirements of the system, requiring an upgrade to a stepper or servo motor system with feedback. A closed-loop system provides precise, high-speed motion profiling and accurate position control. Servo systems provide higher torque at high speeds than steppers and also work better with highly dynamic loads or complex motion applications. For high-performance motion with low position overshoot, the reflected load inertia should match the servo motor inertia as closely as possible. In some applications, up to a 10:1 mismatch is sufficient, but a 1:1 match is optimal. Gear reduction is a good solution to the inertia mismatch problem because the inertia of the reflected load decreases by the square of the ratio, but the inertia of the gearbox must be taken into account in the calculations.
