KEB Elevator & Escalator "KEB COMBIVERT F5"

The compact and powerful KEB COMBIVERT F5 frequency controls/servo controllers provide maximum control over a variety of lifting machines for a smooth yet dynamic drive.

Flexible connection options allow for easy integration in virtually all elevator controls and quick start-up periods.






Filters to Reduce Harmonic Distortion in Elevator Applications.

Due to some products’ long lead times, buildings that require low harmonic distortion must find another alternative. KEB has a full line of available harmonic filters to fill this need in the market. This article expands on the technical features, certifications, and benefits of our filters to reduce harmonic distortion in elevator applications.

What is Harmonic Distortion?

Harmonic distortion comes from VFDs sending current to a motor. The IGBTs inside the VFD create something called pulse width modulation that allows variable control of the speed and torque of a motor. The downside of this PWM is harmonic distortion that, when unchecked, can produce negative effects on a motor and sensitive electronics.

For more info, check out: Harmonic Filters for Reducing VFD Distortion


An Oscilloscope with sinewave harmonic distortion on the screen


How Harmonic Filters Help

The purpose of a harmonic filter is to reduce harmonic distortion and its adverse effects on the motors and other nearby electronics. For elevator applications in a hospital, airport, or  laboratory setting, these electronic distortions can negatively effect other electrical systems such as a building’s heating and air conditioning system.


harmonic filter


KEB Harmonic Filter – Quick Facts

Assembled at KEB

UL Certified device

NEMA 1 rated options for larger units (Enclosure and standalone unit)

Both 230 and 480 voltage class options

Fulfills IEEE 519 Standard

Harmonic Distortion  8%

Low loss design

Improves energy efficiency

Protects drive and regen from line side disturbances or transients

Decreases current ripple on DC Bus capacitors

Increases lifespan and less heating of electrical components





Read more about harmonic filters: Elevator Drive Q & A

Download Product manuals and catalogs on our product page: Harmonic Filters


Harmonic filters are designed to reduce harmonic distortion and KEB’s line of filters fill a need for elevator professionals working on new construction or modernizations. If you want to know more, a KEB elevator application engineer can walk you through the process of selecting a harmonic filter to your elevator machine room and meet your building’s requirements.

Unique Harmonic Filter Design

The KEB 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:

High damping of mainline voltage overshoot
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
Low capacitive reactive power at idle or low loads


UL Rated Harmonic Filter Sizes

KEB harmonic filters utilize three-phase capacitors in a delta configuration. The three-phase capacitor design increases the symmetry and helps to 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 harmonic filters using single-phase capacitors can result in a severe voltage imbalance and cause damage to the VFD input stage.

KEB harmonic filters are available specifically for applications with 480VAC, 60hz mains, or 400VAC (380), 50Hz mains.
KEB harmonic filters are UL rated and available in sizes ranging from 23A to 400Amp rated input current.
All KEB harmonic filters incorporate a circuit protection device on the capacitor banks of the harmonic filter. The capacitor banks are mounted independently of the inductor core assembly to allow for increased mounting flexibility.
Capacitor contactor option available to disconnect the capacitor bank when the machine is idle.
KEB harmonic filters utilize lug-style power connections and can be equipped with a line sync module for use with the KEB R6 line regenerative unit.


KEB Harmonic Filters Performance

KEB has developed a line of harmonic filters designed to be used on the input of a 6-pulse full-wave rectifier. The standard KEB harmonic filter line is designed to reduce the total harmonic distortion (THD) of both current and voltage on the main input line to a maximum of 8%. This level is valid for an Isc /IL ≥ 20.

As an example of the effectiveness of the KEB harmonic filter, the following waveforms show the advantages of using a KEB harmonic filter.


Voltage and current at the mainline – no line choke


Harmonic No Line Choke Current chart

Without a line choke, high current peaks (5 to 10 times the RMS value) occur, resulting in a high ripple current in the DC bus of the motor control. This also means higher ripple voltage on the DC bus 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)


graphic of harmonic line choke impedance

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%


graphic of harmonic with filter - 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 resulting in diode conduction of almost 180 degrees.

The voltage on the DC bus is practically flat, and 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.