What support products does it take to maximize the impact of using VFDs and VSDs? - Part 2
and encoders for closed-loop control. They are designed to support rapid acceleration and deceleration and can support linear or non-linear motion profiles. Many VSDs/VFDs use open-loop control to manage motor speed. They don’t support the precision or responsiveness available with servo motor systems. In addition, open-loop motor control means that VSDs/VFDs don’t necessarily compensate if the load changes or the motor stalls. While servo motor systems are used in highly dynamic applications, VSDs/VFDs are used in applications that maintain a constant speed, or relatively few speed changes, over a long period. Servo motor systems tend to be smaller than VSD/VFD drives, with typical power levels from 40 to 5,000 W. They feature high speeds, up to 5,000 revolutions per minute (rpm), low noise, low vibration, and high torque. Servo motors are available in various frame sizes, up to 180 mm or larger. For example, the SBL40D1-04 from Lin Engineering is a 40 mm, 60 W brushless DC (BLDC) servo motor with a rated voltage of 36 V DC . Servo motors are often paired with drives. Schneider Electric offers the LXM28AU07M3X drive and BCH2LF0733CA5C 5,000 rpm servo motor, both rated for 750 W (Figure 1). The drive features integrated CANopen and CANmotion communication interfaces and can
operate with single-phase or three- phase power. The companion 80 mm motor is IP65 rated and can operate from -20°C to +40°C. Linear and cartesian motion Linear motion is used in various industrial processes, from coating materials and 3D printing to inspection systems, and is available in several embodiments. Some are based on rotary stepper motors, and other designs use linear motors. Rotary stepper motors produce linear motion using a threaded shaft. There are two basic designs, external-nut and internal-nut, sometimes called non-captive.
The nut is mounted on the threaded shaft in an external-nut linear actuator. The shaft is fixed on both ends. As the stepper motor rotates, the nut moves back and forth along the shaft, carrying the object (payload) to be moved. In a non-captive design, the payload is attached to the motor. The shaft is fixed at both ends, and the motor carrying the payload moves along the shaft. Linear motion stages with high- efficiency iron-core linear motors, magnet tracks, and absolute encoder technology can provide repeatable sub-micron precision and 5G acceleration, moving up to 5 m/s for high-speed industrial applications. Unlike threaded
Figure 1: Matched 750 W servo drive and IP65-rated motor. (Image source: Schneider Electric)
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