Active Harmonics Filter
Principle of Harmonics Suppression

Axpert-i-Sine AHF provides 3 phase harmonic current compensation.
Figs. 1 and 2 show the operational principle of the active filter, with which a rectifier load is connected. As shown in fig.1, the active filter is inserted between the load and the source, in parallel to the load. For a six-phase rectifier load, the load current IL appears in a form of rectangular waves, as illustrated in Fig. 2. This can be considered a result of synthesis of the fundamental current IF and the harmonic current IH (Fig. 2).
(IL = IF+IH)
The compensation current IC of the active filter is controlled so that its intensity is the same as that of the above-mentioned IH , and its polarity is just reversed (IC = -IH). As a result, components of harmonic currents contained in the load current are canceled by the effect of active filter, and source current IS remains only to be IF , which is a sinusoidal wave (Fig. 2).
This can be clearly explained by the expression shown below.
IL = IF+IH, IC = -IH
IS = IL+IC = (IF+IH) + (-IH) = IF

Monitoring & Signaling

Axpert-i-Sine is equipped with a user friendly control panel. Self-explanatory full parameter names, easy navigation of parameters through well organized parameter sets & functional keys, 8-selectable parameters on single screen makes it easy to operate and program.

The optional TFT panel with special white back light offers access to all parameters, waveforms & spectrums for management of both Axpert-i-Sine and system power quality. The graphics TFT display & control panel gives easy access to:

  • Load, source & Axpert-i-Sine AHF
  • Monitoring of all metering parameters like V, I, F, kVA, P.F., THD
  • Control commands & settings
  • Waveforms & harmonics spectrum (optional touch screen TFT panel)
  • Status & alarms
Why Axpert-i-Sine Active Harmonic Filter?
  • Fast Fourier Transform based harmonic compensation
  • Operates with closed loop control
  • Harmonics attenuation up to 97% at rated current
  • Reactive power compensation
  • Ability of parallel operation to increase power capacity
  • Voltage-independent harmonic current tracking
  • Inherent current limiting
  • Shunt connection
  • Backlit user interface (optional TFT with touch screen)
  • Modbus RTU communication compatible
  • Advanced programmable digital I/O interface
  • Intelligent control algorithm which dynamically changes the switching frequency to optimize the performance
  • Programmable selective harmonics elimination
  • Best accuracy. Does not require detailed network analysis
  • Prevents possible harmonic resonance
  • Automatic PF compensation, leading as well as lagging, Optimum utilization of power capacity and reduction in kVA demand
  • Adaptive to increase in harmonics current due to additional loads being added
  • More immunity to input voltage distortion
  • Over load condition is prevented
  • Easy maintenance
  • User-friendly operation
  • Facilitates networking ability & Remote monitoring
  • Selective harmonics elimination by digital programming
  • Minimum insertion loss resulting in efficient operation

Amtech’s Multi-Functional Active Harmonic Filter can compensate for reactive currents of fundamental waves, harmonic currents etc. It finds applications in various scenarios with combination of its multi-functions.

Intelligent Buildings

Office Automation equipment, air conditioners, lighting, UPS, elevators, pumping facilities


Crane facilities, press machine, machine tools, high frequency induction heating equipment, inverter-incorporated facilities, printing machines, paper machines

Public facilities and Others

City-water and sewage pumping facilities, harbor crane facilities, crane facilities at waste incineration plants, rope-way hoisting machines, amusement parks etc.

Case Study

Normally 3-phase large UPS with 6-pulse rectifier feedbacks heavy harmonics current of 30%~40% THD into mains or emergency generator. It can cause line voltage distortion or generator malfunction. Axpert-i-Sine AHF is well adapted to operate with large UPS to perform very low harmonic feedback, generating less than 5% current THD.

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