VSD

VSD is an acronym that can refer to several concepts in different domains. The two most common meanings are ventricular septal defect, a congenital heart condition, and variable speed drive, a device used to control electric motor speed. The term may also appear in specialized contexts with other definitions.

Ventricular septal defect (VSD) is a hole in the interventricular septum that allows blood to move from the left ventricle to the right ventricle. It is one of the most common congenital heart defects. Defects are typically classified by location, most often perimembranous or muscular, with less common inlet or outlet types. The left-to-right shunt increases pulmonary blood flow and may cause breathing difficulties, poor weight gain, or heart failure in larger defects. Many small VSDs close spontaneously during infancy. Diagnosis is usually by echocardiography; additional imaging and tests may be used. Treatment depends on size and symptoms. Small defects may be observed; moderate to large defects often require surgical repair or transcatheter device closure. Prognosis is generally favorable after repair, though long-term follow-up is needed for residual shunts, arrhythmias, or valve issues.

Variable speed drive (VSD) is an electrical device that controls motor speed by adjusting supply voltage and frequency. Common control strategies include volts-per-hertz (V/f) control for simple systems, and vector control or direct torque control for precise speed and torque regulation. Benefits include energy savings, smoother process control, and reduced mechanical stress. Typical applications are pumps, fans, conveyors, and machine tools in industry and HVAC. Important considerations include motor insulation, protection, harmonic distortion, cooling, and compliance with electrical standards. Many VSDs are integrated with sensors and control systems for closed-loop operation.

Other uses of the acronym exist but are context-dependent and less common.