PID pump control: Sleep mode saves wear, energy

If your control system uses variable speed pumps in PID loops, there may be conditions where the controller calls for very slow operation, which can harm pumps after prolonged periods of time. Hitachi has created a microdrive that allows a pump in such circumstances to go into a “sleep mode.” This avoids idling pumps during low demand periods and saves energy. Links to explanatory documentation follow.
By Control Engineering Staff September 26, 2008
Hitachi SJ200 Series microdrive at www.hitachi.us/inverters.
Hitachi SJ200 Series microdrive at www.hitachi.us/inverters .

If your control system uses variable speed pumps in PID loops, there may be conditions where the Hitachi has created a microdrive that allows a pump in such circumstances to go into a “sleep mode.”

Hitachi America, Ltd ., Industrial Systems Division, has added this sleep mode functionality to its X200 and SJ200 series microdrives . The company says this functionality is implemented utilizing only the inverter’s built-in PID control, logic, and timing functions as a basis.

Standard PID control may, depending on system demand, allow a pump to operate at undesirably low speeds for extended periods of time, which can cause mechanical issues with certain pump types. In general, it is a wasteful use of energy, since most pumps do not generate significant flow or head at low speeds. Adding sleep mode stops the pump when no pumping is actually taking place.

The implementation requires no additional hardware beyond what is required for standard PID operation. The simple set-up and wiring is described in a pump sleep mode application note , available from the technical support library area of Hitachi America’s Website .

—Edited by Peter Welander, process industries editor, PWelander@cfemedia.com ,
Process & Advanced Control Monthly
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