KEB’s harmonic filter allows users to comply with IEEE 519 power quality standards by reducing VFD distortion. Discover the unique design, features, performance, and sizes of this product below.
Filters and Chokes
Harmonic Filters
Product Details
The Z1 harmonic filter reduces harmonic distortion and its adverse effects. These passive filters can achieve sub-8% THDi levels and improve power quality in systems that use a variable frequency drive.
Features include:
- High-performance electrical grade steel provides 99% efficiency.
- With its passive design, no extra circuitry or controls are required. It can be easily added to existing installations.
- CE and UL listed.
- Graduated sizes are available and can be economically matched to each application.
- Both 50Hz and 60Hz filter designs are available depending on the installation power.
Unique Design
Harmonic filters utilize a patented design incorporating the inductor windings on a common core. This common core design provides the following advantages over competitor harmonic filters and other passive filters:
● High damping of mainline voltage overshoot helps protect sensitive electronics
● Minimal oscillations due to rapid load changes
● Increased lifetime of intermediate DC bus capacitors due to the trapezoidal output of the voltage waveform (less DC bus ripple)
● Negligible DC bus voltage drop at full load
● Parallel operation of several VFDs from a single harmonic filter, supporting scalable installations
● Low capacitive reactive power at idle or low loads
UL-Rated Sizes
Harmonic filters utilize three-phase capacitors in a delta configuration, a topology that offers superior balance compared to single-phase designs commonly found in other passive filters. The three-phase capacitor design increases symmetry across all legs of the circuit. It also helps protect the VFD from voltage surges in the event of a phase failure.
All three phases are disconnected simultaneously in the event of a capacitor failure. A phase failure on a competitor’s filter, which utilizes single-phase capacitors, can result in a severe voltage imbalance. This can cause damage to the VFD input stage.
● Available specifically for applications with 480VAC, 60hz mains, or 400VAC (380), 50Hz mains.
● UL-rated and available in sizes ranging from 23A to 400A, rated for input current.
● Incorporate a circuit protection device on the capacitor banks of the harmonic filter. (The capacitor banks are mounted independently of the inductor core assembly, allowing for increased mounting flexibility.)
● Capacitor contactor option is available to disconnect the capacitor bank when the machine is idle.
● Utilize lug-style power connections and can be equipped with a line sync module for use with the KEB R6 line regenerative unit.
What is the life expectancy of harmonic filters?
The life expectancy of harmonic filters depends on environmental conditions, electrical loading, and system design. However, most passive filters, like these, are rated for 10 to 15 years of service.
Our harmonic filter is engineered with long-life AC film capacitors and high-grade steel cores to ensure durability in even the most demanding industrial environments.
When installed in accordance with guidelines and paired with a properly sized variable frequency drive (VFD), these passive filters can exceed their nominal lifespan while maintaining high power quality.
Temperature sensors and capacitor protection circuits prevent thermal and electrical stress, further extending service life.
Is an active harmonic filter better than a line reactor?
It depends on the application. Active filters are dynamic devices that inject opposing currents to cancel out harmonic distortion in real-time. They are highly effective in systems with nonlinear loads that vary frequently but come at a higher cost and complexity.
Line reactors, in contrast, are simpler passive devices that provide impedance to reduce harmonic distortion. They are cost-effective but offer limited filtering capability, especially at lower harmonic orders.
KEB’s passive harmonic filters bridge this gap by outperforming basic line reactors and offering a robust solution for applications that don't require the expense of active filters.
When your goal is consistent power quality with minimal Total Harmonic Distortion (THDI) and extended Variable Frequency Drive (VFD) lifespan, harmonic filters offer an ideal middle ground.
Enhanced Performance
KEB has developed a line of harmonic filters designed for use at the input of a 6-pulse full-wave rectifier. These passive filters are designed to minimize the total harmonic distortion (THD) of current and voltage on the main input line, reducing it to a maximum of 8%. This improvement enhances overall power quality. This level is valid for an Isc / IL ≥ 20.
With the harmonic filter, the line-side current is sinusoidal. This enhances power quality at the utility interface and supports compliance with IEEE 519 and other international standards.
As an example of the effectiveness of the harmonic filter, the following waveforms show the advantages of using this solution.
Voltage and current at the mainline – no line choke
Without a line choke, high current peaks (5 to 10 times the RMS value) occur. This results in a high ripple current in the DC bus of the motor control. As a consequence, ripple voltage on the DC bus increases, which can lead to torque ripple or reduced torque output from the motor.
Voltage and current with line choke impedance = 3% 480V/60Hz (4% 400V/50Hz)
With inductance (line choke), the peak amplitude of the current is reduced to a range of 3 to 5 times the RMS value. This means a lower ripple current in the DC bus of the motor control. This reduces heating in the capacitors and effectively extends the lifetime by a factor of two.
Voltage and current with the harmonic filter THDI < 8%
With the harmonic filter, the line-side current is sinusoidal.
The peak amplitude of the current is 1.4 times the RMS value. The filter output provides a nearly ideal rectangular voltage and current waveform into the motor control. This results in diode conduction of almost 180 degrees.
The voltage on the DC bus is practically flat. The DC bus capacitors see minimum ripple current, resulting in a further extension of life to 3+ times the nominal.
Furthermore, the average voltage value of the DC bus does not sag much compared to the first two cases. The result is more motor torque at higher speeds.
