Let’s learn about Fuji Electric Frenic-Aqua Inverters

Feature image Frenic-Aqua Inverter

Fuji Electric FRENIC-Aqua inverters are specialized for water treatment systems. In this article, let’s find out more details about this inverter model.

Fuji Electric FRENIC-Aqua inverter product series:

Standard type (with built-in EMC filter)

This series has a capacity of 0.75 – 710kW (IP21 or IP55 protection structure can be selected in the range of 0.75 – 90kW.)

Integrated DCR filter + EMC filter

Power from 0.75 – 90kW (IP21 or IP55 protection structure can be selected within 0.75 – 90kW).

Components of an Fuji FRENIC-Aqua inverter:

  1. User-Friendly, easy-to-see , and dedicated keyboard:

Multi-language support, outstanding HELP function, unit setting with SV and PV values, data copy (3 types). Also the keyboard is detachable or mounted on the control panel (using an optional cable).

  1. Control board

  • Equipped with USB port, BACnet is equipped as standard.
  • Up to 3 types of integrated optional boards can be attached all together.
  • Optional battery connection
  • Various communication options
  1. Control terminal block

Detachable control terminal block is accepted. This allows the device to be easily replaced without disconnecting the cable.

  1. Capacitor board

Output a signal that predicts a lifetime to reduce capacitor capacity and cumulative running hours. This allows users to capture replacement times.

  1. Cooling fan

The cooling fan of the Frenic-Aqua inverter is easily replaced because it is mountable. You can also optionally turn ON or OFF the fan. This feature helps to increase the life of the device.

  1. EMC filter

This filter helps to reduce equipment noise when operating significantly, in compliance with IEC61800-3.

  1. DCR

Drastically reduces harmonic noise. Compliance with IEC / EN61000-3-2 and IEC / EN61000-3-12 standards. Supplied as standard (for models up to 90kW) and can be mounted as an optional option.

  1. Environmental immunity

Support 3C2, IEC60721-3-3

  1. Other

Software support / analysis by downloader, RTC backup by battery (optional)

Structure of Frenic-Aqua inverter

The outstanding functions of FRENIC-Aqua inverters

Optimal control by the energy saving function

  • Linearization function
  • Control temperature difference constant and control pressure difference
  • Energy-saving functions include wet bulb temperature control
  • Automatic energy-saving operation

Dedicated pump control functions are provided as standard

  • 4PID control
  • Adjustments by step
  • Mutual effect
  • Maximum startup control per hour
  • Detected dry pump
  • Deceleration time to check protection valve
  • Slow flow function
  • Curve detection ends
  • Enhanced functionality
  • Acceleration and deceleration in the initial stage

Compact design

  • The first slim body design among Fuji Electric inverters.
  • The first inverter series has the same dimensions between IP21 and IP55.

User friendly, useful functions

  • Fire mode (mandatory operation)
  • Custom logic
  • Sensor operation function
  • Anti-jamming
  • Vector control
  • Password function
  • Real-time clock
  • Useful, user-friendly keyboard

Widely used for water treatment

  • Water and wastewater purification plant, clean water and sewage

Wastewater purification plant

Wastewater purification plant

  • Water system

Water system

Water system

  • Desalination of sea water

Desalination system

Desalination system

Fuji Electric provides highly reliable frequency converters with precise technical support. Products that meet the complex needs of water treatment. They require stable water supply and efficient use of resources.

FRENIC-Aqua inverters have the specialized functions required by standards in water treatment plants. Examples include 4PID control, step adjustment, dry pump detection, slow flow function ,and operating sensor. Besides, there are many other options. These functions strongly contribute to system protection and reduce costs.

The pumps and blowers used in water purification, water supply and wastewater treatment plants need to be controlled with precise pressure (discharge pressure). FRENIC-Aqua inverters perform optimal process control with high integrity with the integrated PID controller.

The step adjustment function can control up to 8 units + 1 auxiliary motor. This allows applying to large-scale systems. In addition, because the operating time of each pump and blower is balanced in step adjustment, the system life can be extended.


Characteristics of using pumps Advantages
· Stratification control (Maximum of 8 units + 1 auxiliary motor)

· (Uniformizing operating hours)

· Cut the cost

· Longer system life

Integrated PID controller · Process optimization

· Cut down the costs

Detecting dry pump · Pump protection

· Energy saving

Mutual effect Cut down on initial costs
Condensation prevention function No need for a heater

Blowing machine

Characteristics of using fans Advantages
Automatic energy-saving operation (by load) Energy saving


Built-in PID controller · Process optimization

· Cut down the costs

Condensation prevention function No need for a heater
Sensor operation function Blower protection


  • Liquid pressure device
  • Oil pumping system
  • Injection machine
  • Hydraulic pressing machine
  • Extruder
  • Refrigerated air compressor

Optimal structure design

Dedicated, friendly keyboard

Regulators are specified by LCD extension

  1. Present value (PV)
  2. Setting value (SV)
  3. Manipulating Value (MV)
  4. Frequency
  5. Output current
  6. Output voltage
  7. Torque
  8. rotation speed
  9. Power consumption
  10. Cumulative energy

User-friendly and easy-to-use keypad

User-friendly and easy-to-use keypad

Multi-language supported

19 languages + user customized language (Tentative)

Japanese English Chinese German French Spanish
Italian Russian Greek language Turkish Bahasa Malaysian Vietnamese
Siamese Indonesian language Polish Czech Swedish Portuguese


Real time clock (RTC) is provided as standard

  • Alarm information with date and time
  • Alarm information of the last 10 times are stored and displayed by date and time.
  • Timer function
  • A maximum of 4 timers can be set for a week.
  • You can set the rest day (20 days a year).

Optimal function for using in water treatment

Adjustments by step

Step adjustment is the function of controlling multiple pumps by an inverter. The pumps are driven with a combination of inverter motors and commercial motors. This can be applied in a large-scale water treatment plant.

In step adjustment, the signals of the flow rate and the pressure sensor are controlled by the PID regulator integrated in the inverter. Each pump is controlled by the inverter according to the switching signal from the inverter. The pumps are controlled only by the inverter when the discharge volume is small and added to the inverter motor. They are controlled by commercial engines by adding one at a time when the discharge volume is larger to ensure the total amount of discharge needed.

Step adjustment function of FRENIC-Aqua inverter

Step adjustment function of FRENIC-Aqua inverter

Two methods of adjusting the inverter motor

Method of fixing the inverter motor

The system is configured by combining an inverter-controlled motor (M0), a commercially controlled motor (from M1 to M8) and an auxiliary motor (MA). The motor driven by the inverter is always fixed as the M0 motor. Commercially controlled motors are added individually one by one when the required discharge flow rate can only be achieved with the M0 motor.

Mobile method of inverter motor

The system for this method is configured by combining motors that can be switched between inverter and commercial (M1 to M4) and commercially controlled auxiliary motors (MA). The motor is controlled by the inverter with variable speed control when starting. When the desired discharge rate cannot be achieved with the first motor, FLOATING-1 or FLOATING-2 operations can be selected.

Mutual effect

The system can be configured without using the controller by connecting the inverter via contact. In this system, if an error occurs with the main drive, the next drive is controlled as the main drive. Moreover, the wiring system can be saved with the use of communication services. This eliminates the need for additional options by using Modbus RTU communications.

Customizable logic

A customizable logic interface function is provided for the body ofthe inverter. This allows the formation of logic circuits and arithmetic circuits for digital and analog input and output signals, allowing the construction of simple relay chains while processing signals freely.

Enhanced function

The frequency can be strongly output at a fixed rate for PID control. By setting the operating frequency, the operating time and the acceleration time at the start, the optimum operation will be set to start the pump. Turbocharging can be applied for a specified period of time at the start.


The function codes can be read / written, displayed or hidden by setting 2 passwords. This prevents misoperation or overwriting of the function code. In addition, if the password is entered incorrectly beyond the specified number of times, the inverter will be restricted from operating.

Detecting dry pump

The pump dry condition can be detected from the PID deviation value by setting the output frequency, output current and flow rate sensor value. Water leakage and pressure drop due to impeller damage can also be detected.

Slow-flowrate function (turbocharged operation available before slow flow rate)

The inverter may stop when the discharge speed is low due to increasing the discharge pressure of the pump. Tank pumps can make the downtime longer by applying pressure just before stopping. This will helps saving energy.

Initial acceleration/deceleration time

Pumps operating at low speeds for a long time may be damaged by large loads during low speeds. Fuji Electric FRENIC-Aqua inverters can provide specific acceleration / deceleration times to avoid prolonged pump operation.

FRENIC-Aqua inverter anti-jamming function

The engine will reverse rotates in case of any abnormal problems. Such as stuck. If sand or dust is trapped in the pump gear, overcurrent protection is activated. The motor is then turned in the opposite direction so that sand and dust are pushed out of the impeller. After that, the engine continues to rotates normally. This allows water to be supplied normally.

Deceleration time for protecting the check valve

If a valve is closed quickly after stopping the pump, there is a risk of damaging the check valve (piping, pump, valve, etc.) due to water hammer. To protect the check valve from this, the pump speed slows down as the check valve closes.