Understanding the main types of loads, motors and applications can help simplify the selection of industrial motors and accessories. There are many aspects to consider when choosing an industrial motor, such as application, operation, mechanical and environmental issues. In general, you can choose between AC motors, DC motors, or servo/stepper motors. Knowing which one to use depends on the industrial application and whether 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 speed required, and acceleration/deceleration - especially if fast and/or frequent - will determine the torque and horsepower required. The requirements for controlling motor speed and position also need to be considered.
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 gear pumps. In these applications, the torque is constant because the load is constant. The required horsepower may vary depending on the application, which makes constant speed AC and DC motors a good choice.
2, Variable torque and constant horsepower: An example of variable torque and constant horsepower applications is machine rewinding paper. The speed of the material remains the same, which means the horsepower doesn't change. However, as the diameter of the roll 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 determining the size of an industrial motor or selecting an energy control method. 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 need variable horsepower and torque. As the speed of an industrial motor increases, the load output also increases with the required horsepower and torque. These types of loads are where the motor efficiency discussion begins, with inverters loading AC motors using variable speed drives (VSDs).
4, position control or torque control: Applications such as linear drives, which require precise movement 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 commonly used in steel or paper production lines and similar applications.
Different industrial motor types
Although there are more than 36 types of AC/DC motors used in industrial applications. Although there are many types of motors, there is a great deal of overlap in industrial applications, and the market has pushed to simplify the selection of motors. This Narrows the practical 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 winding rotor motors, servo and stepper motors. These motor types are suitable for the vast majority of applications, while other types are used only for special applications.
Three main types of industrial motor applications
The three main applications of 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 maximum speed is less than the reference speed of the motor, a gearbox is required. This also allows a smaller motor to run at a more efficient speed. While there is a wealth of information online on how to determine the size of a motor, there are many factors that users must consider because there are many details to consider. Calculating load inertia, torque, and speed requires the user to understand parameters such as the total mass and size (radius) of the load, as well as friction, gearbox loss, and machine cycle. Changes in load, speed of acceleration or deceleration, and duty cycle of application must also be considered, otherwise industrial motors may overheat. Ac induction motors are a popular choice for industrial rotary motion applications. After motor type selection and size, users also need to consider environmental factors and motor housing types, such as open frame and stainless steel housing washing applications.
How to select industrial motor
Three main problems of industrial motor selection
1. Constant speed apps?
In constant-speed applications, the motor typically runs at a similar speed with little or no consideration for acceleration and deceleration ramps. This type of application typically runs using full-line on/off controls. 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 offer 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 a servo or stepper motor would be considered excessive for a simple application.
2. Variable speed app?
Variable speed applications typically require compact speed and speed variations, as well as defined acceleration and deceleration ramps. In practical applications, reducing the speed of industrial motors, such as fans and centrifugal pumps, is usually done to improve efficiency by matching power consumption to the load, rather than running at full speed and throttling or suppressing output. These are very important to consider for conveying applications such as bottling lines. The combination of AC motors and VFDS is widely used to increase efficiency and works well in a variety of variable speed applications. Both AC and DC motors with appropriate drives work well in variable speed applications. Dc motors and drive configurations have long 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 useful in low speed applications because they can provide full torque at low speeds and constant torque at various industrial motor speeds. However, the maintenance of DC motors is an issue to consider, as many require commutation with brushes and wear out due to contact with moving parts. Brushless DC motors eliminate this problem, but they are more expensive up front and the range of industrial motors available is smaller. Brush wear is not an issue with AC induction motors, while variable frequency drives (VFDS) provide a useful option for applications exceeding 1 HP, such as fans and pumping, that can increase efficiency. Choosing a drive type to run an industrial motor can add some position awareness. An encoder can be added to the motor if the application requires it, and a drive can be specified to use encoder feedback. As a result, this setup can provide servo-like speeds.
3. Do you need position control?
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 inherent feedback. The stepper moves precisely to a position at a moderate speed and then holds that position. Open loop stepper system provides powerful position control if properly sized. When there is no feedback, the stepper will move the exact number of steps unless it encounters a load interruption beyond its capacity. As the speed and dynamics of the application increase, the open-loop stepper control may not meet the requirements of the system, which requires upgrading to a stepper or servo motor system with feedback. A closed-loop system provides precise, high-speed motion profiles and precise position control. Servo systems provide higher torques than steppers at high speeds and also work better in high 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 much as possible. In some applications, a mismatch of up to 10:1 is sufficient, but a 1:1 match is optimal. Gear reduction is a good way to solve the inertia mismatch problem, because the inertia of the reflected load is dropped by the square of the transmission ratio, but the inertia of the gearbox must be taken into account in the calculation
Post time: Jul-10-2023