The design combines an AC induction motor with a Variable Frequency Drive (VFD inverter) mounted on the motor. Combining the motor & drive together is claimed to be simple to use while being highly accurate and repeatable. Wanner says that because Hydra-Cell pumps are true positive displacement pumps, flow rate is directly proportionate to input shaft speed and virtually independent of system discharge pressures.
Hydra-Cell® P300 Metering Pump with Electronic VFD Control. Flow rate can therefore be varied proportionately by motor speed control offering turndown ratios of 10 to 1 or better. A variety of control methods is available from a local analogue control knob, graded from 0 to 100% to the Wanner “Control Freak”, which enables programming for flow rate or totalisation via multiple Variable Frequency Drives (VFDs).
Other flow rate adjustments options are available, including manual speed variators (suitable for ATEX environments), and electronic VFDs with on-board key-pad controllers with flow rate display and removable, hand-held key-pad controllers for authorised personnel only. All Hydra-Cell metering and dosing solutions exceed the performance requirements of API 675 in terms of steady state accuracy (±1%), Linearity (±3%) and Repeatability (±3%).
