In economics, cross-sectional studies typically involve the use of cross-sectional regression, in order to sort out the existence and magnitude of causal effects of one or more independent variables upon a dependent variable of interest at a given point in time.
VARIABLE-FREQUENCY DRIVE. A viable-frequency drive is an electronic controller that adjusts the speed of an electric motor by. modulating the power being delivered. Variable-frequency drives provide continuous control, matching motor speed to the specific demands of the work being performed.
Program Scope. This program applies to Variable Frequency Drives as defined below, for which published ratings are available, and which can be tested in the Independent Third-Party Laboratory contracted by AHRI. Variable Frequency Drive.