Enjoypow Active Harmonic Filter Selection

10 FAQ of Active Harmonic Filter Selection

In the power quality industry, there are many issues to consider when Selectting the right active harmonic filter. This article lists some common problems of active harmonic filter selection and interpretations for your reference.

FAQ: Can power factor correction capacitors (PFCC) be used with Active Harmonic Filters?

Power factor correction capacitors can be used in systems with AHF, we call it as hybrid var compensation solution. Harmonic suppression of the AHF may even be required to protect the PFCC from overheating and failure caused by harmonics.

PFCCs cannot be installed on the load side of AHF current sensors. The PFCC should be installed between the AHF and the point of common coupling (PCC).

FAQ: What is the main function of Enjoypowers active harmonic filter?

The Three main functions performed by the Enjoypowers AHF are:
Harmonic Mitigation
Power factor correction
Three-phase unbalance adjustment

FAQ: Enjoypowers’ active harmonic filter use 3-level inverter?

Enjoypowers’ AHFs all use 3-level inverters. Compared with 2-level , it has the following advantages:

  • The equivalent switching frequency is high, the ripple current is small, and the output power quality is better;
  • Small inductance value; small loss and high efficiency;
  • The device has low withstand voltage, can be applied to higher voltage levels, and has low loss;
  • Small size and high power density;

FAQ: Is the active harmonic filter connected in series or parallel to the load?

Active harmonic filters are connected in parallel with the load. The filter can be powered off or even replaced without affecting the operation of the load.

FAQ. Can active harmonic filters be combined in parallel for larger harmonic loads?

Yes, up to 20 modules can be combined in parallel. For example, five 100A AHFs form a 500A system.
A parallel connected AHF system requires only one set of current transformers(CT).
The module is connected in parallel with the module, and a standard network cable is required.

FAQ. How many CTs are needed for an active filter?

CT is used with AHF to continuously monitor load and harmonic currents. If sampling on the load side, you need to configure one set of CTs; If sampling on the power supply side, you need to configure two sets of CTs. AHF was subtracted by 2 sets of CT values. The size of the CT depends on the current rating of the bus.

2 Sets CTs are needed for an active harmonic filter
2 Sets CTs are needed for an active harmonic filter

FAQ. Do Active Harmonic Filters (AHF) have the capability to target specific individual harmonics?

There is no need to target a specific single harmonic, as the AHF automatically detects the 2-50th harmonic and injects corrective currents for all harmonics.

FAQ. What happens if the load produces more harmonic currents than the size of the active harmonic filter?

The AHF will limit its harmonic cancellation current output to a safe level. Additional harmonic currents will not be canceled, the system THDi will increase, and the filter will not overload and fail.

FAQ. Can Active Harmonic Filters be used in with Passive Harmonic Filters

AHF can be installed on electrical systems that already have PHF installed on some system nonlinear loads.
PHF removes some of the harmonics generated by non-linear loads connected to PHF. When the AHF is installed in parallel with the system mains, the balance of the residual harmonic currents in the system will be detected by the AHF’s current transformers.
The AHF will inject a correction current into the main bus to reduce the measured harmonic currents to a level that meets the IEEE 519 standard at the main bus terminals. The combination of PHF and AHF is called a hybrid solution and is used in many applications.

FAQ. how to Size of Active Harmonic Filter Selected for VFD

Harmonic mitigation for a VFD is not an easy task, and there are many factors that affect the final result. In order to accurately size the active harmonic filter, the following information is required:

  • Circuit diagram of the system, including the location and capacity of the VFD and power factor correction;
  • Detailed equipment lists are also available, especially in combination with one-line diagrams.
  • VFD specific information, including total power, rated current and actual current;
  • Does the VFD use a reactor and what is the impedance?
  • Is there a large soft start load, is there a generator?
  • Is the installation environment of the active harmonic filter harsh? If yes, need to choose industrial grade active harmonic filter

Click power quality application  for more active harmonic filter applications.

Enjoypowers is a top power quality manufacturer in China, providing OEM services for power quality products to more than 480 partners. Enjoypowers’ products have been successfully delivered in more than 20 countries。Enjoypowers Technology has a large number of power quality application cases around the world.

If you are selecting an active harmonic filter, you can contact us and let an active harmonic filter expert guide you through the selection and configuration.

For this, please send us your application data and contact me: [email protected], Or connect with me on LinkedIn.

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