A variable-frequency drive (VFD) is a system for controlling the rotational speed of an alternating current electric motor by controlling the frequency of the electrical power supplied to the motor. Variable-frequency drives allow operators to fine-tune their processes while reducing the cost of energy and equipment maintenance. 

VFD’s are quite useful to the water and wastewater industries because they can be used with the pumps, conveyors and drives involved in pumping and aeration applications. For instance, pumping uses excessive energy and cause significant wear-and-tear on equipment. Use of VFD drives enables pumps to accommodate fluctuating demand, running pumps at lower speeds and drawing less energy while meeting demand.

MultiTrode has developed an innovative VFD algorithm which makes it very easy to setup a VFD station. The standard application uses one 4-20mA control loop through each drive. The MultiSmart Pump Station Manager algorithm then provides a smooth power curve as levels are increased and decreased regardless of how many pumps come online.

For example, the lead (duty) pump starts at 50%, and at the level where it is running at 100% the lag (standby) pump starts. A lot of applications would start the lag pump at 50% and keep the lead pump at 100%. What the MultiSmart VFD algorithm does is start the lag pump and bring the speed of both to 75%. (And note that all of these parameters like start speed and level for 100% speed are user adjustable)

Therefore, multiple pumps will always be running at the same speed, and the speed will be adjusted depending on how many pumps are running.

Setup of this module is simple, with only the following values needing to be setup for each pump:

• Start speed, %
• Level at 100% speed

Some additional features help to optimize the station:

• Manual (hand) speed (to ensure that pumps run at full speed for manual/hand mode)
• Fixed speed value and duration if required, e.g. to clear pipes by running pumps at 100% for 10 seconds initially

Read more…

In the well MultiSmart, pump station, Variable-Frequency Drives, VFD, wastewater, water