VFD In Pump Applications

When in use, the pumps are always part of a pumping system.
A pumping system is usually a network of pipes, tanks, valves
and other system parts. The receiver is usually at a higher geographic
level than the supply of the system. These parts can be
also on the same level, as in the case of a closed circuit heat
transfer system.
Pumping systems nearly always require a variation of fl ow rate.
Examples include the daily cycle in the consumption of drinking
water, the varying process demand for a liquid or seasonal
heating demand. However, the variation required may be in the
pump head, such as for cyclical changes in process pressure,
or pumping to tanks with a variable liquid level.
In spite of the variations, the pump capacity is selected according
to the maximum fl ow and head or even to the future needs,
perhaps with a certain safety margin.
The average pumping capacity may be only a fraction of the
maximum capacity and this will require some kind of control.