Variable Frequency Drives
Efficiency ● Control ● Reliability
As an alternative to pressure control valves or frequent pump cycling that inefficiently control pump output to meet system demand, VFDs match pump speed and performance with system demand by varying power frequency and voltage supplied to the pump based on inputs from pressure transducers, flow meters, and level sensors.
The result: Less energy usage, greater efficiency, higher reliability, lower
maintenance costs, and improved pumping system control
How VFDs work: The Affinity Laws of Centrifugal Pumps
Centrifugal Pumping Systems have fixed relationships between the performance characteristics of speed, flow, head, and energy.
The Affinity Laws state that for any change in pump speed:
Flow change is proportional to the speed change
Pressure (head) change is proportional to the speed change squared
Power (energy) change is proportional to the speed change cubed.
Or simply stated, for a 10% reduction in pump speed:
Flow will be reduced by 10%
Pressure (head) will be reduced by 19%
Power (energy) will be reduced by 27%
When the system demand is less than the pumps' rated capacity, why run them at 100% only to throttle flow and pressure?
Controlling system pressure with Pressure Control Valves is like driving your car with your foot on the gas while controlling your speed with the brakes.
Efficiency & Reliability. Every pump operates on a "Pump Curve" that relates the flow and pressure (head) generated for that pump based on the pump's speed and impeller diameter. On each pump curve is a combination of pressure and flow where the pump will operate most efficiently, the Best Efficiency Point or BEP.
Pumps operating within the Reliability Curve or Preferred Duty Zone, at or near the BEP will experience less wear and require less maintenance. Conversely, pumps operating outside those limits will experience high temperatures, cavitation, low bearing and seal life, lower impeller life, and recirculation.
VFDs maintain pump performance at the BEP by controlling pump speed to meet system pressure and flow demand while improving system life and reliability.
VFD Control Strategies & Configuration
Variable Frequency Drives (VFD) provide motor control by varying the frequency and voltage of the power supplied to the pump motor. By matching the motor speed with required pump performance, energy reductions of 30% or more can be achieved.
Variable Frequency Drives support a range of control strategies beyond basic energy efficiency. VFDs can be programmed to respond to multiple sensor inputs such as pressure, level, flow, and combinations of inputs indicating failure conditions.
Properly configured VFDs will optimize pump performance by maintaining head and flow at or near its Best Efficiency Point (BEP). Operation at or near the BEP will reduce cavitation, bearing and seal wear improving reliability and reducing maintenance costs.
Optimization & Reliability
NAVI has partnered with Yaskawa America to provide the highest quality, intelligent, integrated software VFDs available. Yaskawa iQpump Variable Frequency Drives installed by NAVI are unique in that they utilize integrated control software, specific to pumping systems, and require no external PLCs or other control devices. VFDs will constantly regulate pump performance to meet demand for flow and pressure rather than running pumps at constant speed then regulating flow and pressure with control valves. Yaskawa drives provide control, energy efficiency, and a broad range of operations measurements, analytics, and diagnostics. Intelligent VFDs provide a platform for telemetry, SCADA, and alarm systems.