Using an inverter to control pump stations

Pump Station

Advantages of using an Inverter to control pump stations

What are the advantages of using a Mitsubishi Electric Factory Automation Inverter to control pump stations?

The FR-F800 series inverter has special features for controlling pumps such as load curve automatic detection, advanced PID control, and cleaning function.

Automatic detection of load curve

The automatic detection of the load reference is a multi-point detection of the curve, based on the real load curve, and is extremely precise in its definition. This allows us to measure any congestion or obstructions inside the pipeline/pipe in which the water flows (overload) or to measure any problems in the mechanical transmissions (underload for possible belt breakage). In this way, the risk of an unexpected shutdown of the water supply is extremely low. The cleaning maneuvers are automatic, without having to remove the pump, reducing the time required and the related cost. The analysis of the load curve also allows having pre-alarms for imminent faults, further reducing emergencies and allowing a careful maintenance planning

Control
Dry Run
Sleep

Advanced PID Control

The advanced PID controller can be used for different special functions:

PID pre-charge function: This function drives the motor at a certain speed before starting PID control. This function is useful for a pump with a long hose. Without this function, PID control would start before the pump is filled with water and proper control would not be performed.

Fireman mode: the “Fireman” mode consists in inhibiting each alarm from the possibility of interrupting the operation of the inverter. In this mode, the inverter operates at its maximum power until the end of the emergency or the breakage. It is an indispensable feature for the operating of the pumps in fire protection systems.

Sleep function: when the frequency, after the PID calculation is lower than the set level for a predetermined time frame, the inverter functions are suspended, thus allowing to avoid energy inefficiencies related to the excessive consumption in the low-speed range.

PID “dry run” monitoring function: This function can prevent operation without water in the pipes by monitoring the flow rate (measured value) inside the pipes. When the flow rate decreases while the FU signal is ON, an output signal is sent for notification. The dry run signal (DRY) is output during PID control when the measured value is lower than the lower limit.

Through the advanced PID regulator, it is possible to progressively fill a pipe, avoiding the water hammer. Moreover, when the pump is stopped, slow deceleration can be applied to the predetermined section to prevent the water hammer caused by closing the valves. The inlet pressure is constantly monitored, if a lowering is detected below preset limits a warning signal is shown, and if the situation persists, corrective actions are powered up to prevent the pumps sucking air. Breakages in the pipes are identified and reported. In addition, some functions are available to activate pre-alarms for exceeding the maximum/minimum frequency values of the inverter and to limit energy consumption due to continuous accelerations and decelerations (hold function).

Cleaning Function

This is a function to remove stains or foreign matter on the impellers or fans of pumps by setting a forward/reverse rotation sequence.

Advantages

  • Reduction of management costs
  • Less energy consumption
  • Reduction of extraordinary maintenance intervention
  • Timely detection of malfunctions

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