Active Harmonic (Power) Filter

Active Harmonic (Power) Filter2020-10-05T04:15:04+00:00

Active Harmonic Power FilterAPF Principle
Delta’s PQC Series APF is connected in parallel with non-linear loads, and uses one set of current transformers (CT) to detect the load current. It calculates each order harmonic current by FFT algorithms in its DSP microchips, and then generates a compensating current with the same amplitude but opposite phase angles to the detected harmonic current, which cancels out the original load harmonics.

The PQC series APF not only eliminates harmonic current from the load side, but it also mitigates harmonic voltage caused by harmonic currents. The APF system can also improve power factor (PF) and correct load imbalances in the power system.

APF Principle

APF Structure

Delta PQC Series APF has a modular design. Usually the Delta active power filter system consists of one or several APF modules and an optional Liquid Crystal Monitor & Control Panel (LCM). Each APF module is an independent harmonic filtering system, and users can change the harmonic filtering system rating by adding or removing APF modules.

According to the mounting type, Delta PQC series APF can be divided into Modular APF and Wall-mounted APF.

Modular APF

APF modules and an LCM panel can be embedded in Delta’s standard APF cabinet or a customized cabinet. There are breakers, cable terminals and Surge Protection Device (SPD) in the APF cabinet.

According to cable terminal type, a modular APF can be divided into two types:

  • Draw type modular APF (hot-swappable)
  • Fixed type modular APF (not hot-swappable)

Modular APF

Wall-mounted APF

Delta’s Wall-mounted APF can be installed on a wall, which is suitable for low rating applications, and an optional LCM
panel can be fixed on the all-mounted APF according to customer requirements.

Wall mounted APF


Rated Voltage : AC 400V, AC 690V

Electrical Specification
Input Voltage Range
AC 400V : AC 308V~480V
AC 690V : AC 432V~880V

Electric Connection
AC 400V : 3P3W/3P4W
AC 690V : 3P3W

Rated Frequency : 50Hz (60Hz) +/- 10%
Input Voltage THD Range : ≤15%

Rated Current per Module
AC 400V : 50Amp, 75Amp, 100Amp
AC 690V : 100Amp

Rated Current per Cabinet
AC 400V : 50~525Amp (module combination)
AC 690V : 100~500Amp (module combination)

Redundancy : Each module is an independent filtering system

Harmonic Elimination Range
AC 400V : 2rd ~ 50th order (Selectable)
AC 690V : 2rd ~ 31st order (Selectable)

Harmonic Filtering Degree
0 ~ 100% programmable per harmonic in Ampere value

Harmonic Filtering Performance
Filter up to 98% harmonics at rated load, THDv<3%, THDi<5% after filtering

Reactive Power Compensation Capability
Both inductive and capacitive reactive power

Reactive Power Compensation Performance
PF≥0.99 after compensation (if the APF capacity is sufficient)

Imbalance Correction Capability
AC 400V : Mitigate negative and zero sequence
AC 690V : Mitigate negative sequence

Full Response time : <20ms
Instant Response time : <100us Thermal Loss : ≤3% of APF rated capacity (kVA) Output Current Limitation : Automatic (100% rated capacity)

Parallel Expansion(System)

AC 400V : Up to 10 Racks(7 modules per cabinet)

AC 690V : Up to 10 Racks(5 modules per cabinet)

MTBF : >100,000 hours

Control Technology
Switching Frequency
AC 400V – 50A, 75A : 60kHz
AC 400V – 100A : 30kHz
AC 690A : 20kHz

Controller : DSP control
Communication : Modbus Protocol, RS232/485
Monitoring : PQC Monitor Software (Optional)

Physical Specification
IP Grade of Cabinet : IP20, IP30 or customization
Cooling method : Intelligent forced air cooling

Noise Level
AC 400V : < 65dB(A) @1m (Module)
AC 690V : < 70dB(A) @1m (Module)

Dust Filter : Optional
Dimension : Refer to APF Model table
Weight : Refer to APF Model table

Environmental Requirement
Ambient Temperature : -10~50 ℃
Relative Humidity : 0~95%
≤ 1000m Rated Capacity,
1000-2000m (derating 1% per 100m)

All specifications are subject to change without prior notice.

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