What type of motor controller regulates speed and operates over a predetermined range?

A variable speed controller is designed specifically to regulate the speed of a motor within a predetermined range, allowing for adjustments according to the operational needs of the system. This type of controller enables the user to manage the speed effectively, providing both flexibility and efficiency in various applications. It utilizes different techniques to control the power supplied to the motor, which can include changing the voltage, frequency, or both, thereby allowing for smooth transitions between speeds.

In contrast, an across the line controller typically starts the motor directly at full voltage, meaning it does not have the capability to regulate or vary the motor speed. An emergency run controller is primarily focused on allowing motors to run under emergency conditions, without features specifically aimed at routine speed control. A frequency inverter does regulate speed and is closely related to variable speed controllers, but it specifically converts DC to AC power and adjusts the frequency of the power to control speed, making it more specialized than the broader category that a variable speed controller can represent. Therefore, the choice of a variable speed controller captures the general concept of speed regulation across various types of applications.