Motor Speed Control Using Variable Speed Drives (VSD)
SELECTION SUPPORT. INTEGRATION. INSTALLATION. MAINTENANCE.
While the PLC manages plant-level logic, operating sequences and process decisions, a variable speed drive, or VSD, controls the speed and torque of an electric motor. It does this by converting the fixed-frequency electrical supply into a controlled, variable-frequency and variable-voltage output suited to the motor and application.
Overberg Industrial Control provides VSD selection support, configuration, PLC integration, installation, commissioning and fault-finding for new and existing industrial motor-control systems. Applications may include pumps, fans, conveyors, mixers and other motor-driven equipment where controlled acceleration, deceleration or variable-speed operation is required.
We are proficient in VSD platforms from Siemens, Schneider Electric, Allen-Bradley, WEG, Yaskawa and Delta. Drive selection is based on the motor, driven equipment, load characteristics, process requirements, electrical supply, control method and existing automation platform.
How a Variable Speed Drive Works
An AC motor connected directly to a fixed-frequency electrical supply generally operates at or near a fixed speed. A VSD allows the motor speed to be varied by controlling the frequency and voltage supplied to the motor. The drive can therefore accelerate, run and decelerate the motor according to the requirements of the process.
The correct control method depends on whether the motor must maintain a process value, follow a production sequence or operate at a manually selected speed.
The VSD can receive its speed command from several sources, including:
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A PLC
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A built-in PID controller
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A local keypad
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An HMI or SCADA system
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An analogue process signal
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Digital preset-speed inputs
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An industrial communication network
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A manual speed reference
Discuss Your Motor-Control Requirement
A successful VSD installation begins with a clear understanding of the motor, driven equipment and process requirement. When contacting Overberg Industrial Control, please provide the motor nameplate information, existing starting method, application type, required speed range and details of the installed PLC or control system.
Photos of the motor, control panel and existing drive can assist with the initial assessment. Please also indicate whether the project requires process instrumentation, PID control, PLC integration, remote monitoring or replacement of an existing VSD. This information will help define the appropriate drive, electrical and control-system architecture.