Which equipment is used for variable speed control in pumping systems?

The variable frequency drive (VFD) is the correct choice for variable speed control in pumping systems. VFDs work by adjusting the frequency and voltage supplied to the electric motor, allowing the motor's speed to be varied based on the operational needs and conditions of the system. This capability is essential for optimizing energy consumption, improving process control, and reducing wear on equipment through smooth acceleration and deceleration of the pump.

In pumping applications, the use of a VFD can lead to significant energy savings, especially in systems that do not require constant flow rates. By matching the pump speed to the system demand, operators can avoid the inefficiencies associated with running pumps at full speed when less capacity is needed.

Considering the other options, while a programmable logic controller (PLC) can control pumps and may work alongside a VFD, it does not inherently provide variable speed control. A geographic information system (GIS) is used for mapping and analyzing spatial data and is unrelated to pump control. Hand-off-auto controls refer to different operating modes for equipment rather than specifically providing variable speed capabilities.

Thus, the variable frequency drive stands out as the essential equipment for achieving variable speed control in pumping systems, enabling efficient and effective pump operations.