Output filters – also called motor filters because they are installed upstream of the motor – are critical components in electrical engineering. They serve to minimize unwanted noise and harmonic distortion in electrical systems. They help improve the efficiency and service life of motors and other electrical devices. By filtering out this noise, motor filters ensure stable operation, reduce energy loss, and protect sensitive components from damage.
For proper and trouble-free operation!
dV/dt chokes
Three-phase output chokes
- Current ratings from 2 A up to 2300 A
- Rated voltage 400 V (also bis 690 V available)
- Connection via copper busbars from 400 A
- Recommended for frequency inverters with short motor cables
- Limitation of dV/dt-values (voltage peaks)
- Emissions to other cables is reduced
- Increases the life time of motors driven by inverters
- UL approval for USA and Kanada from 2 A up to 10 A and from 24 A up to 90 A
| File | Size |
|---|---|
| Data_Sheets » EMC » Motor_Chokes | |
| EPA_du_dt-chokes_DUDTN_124-2300_data-sheet.pdf | 3.11 M |
| EPA_du_dt-chokes_DUDTN_2-110_data-sheet.pdf | 3.53 M |
OC
Ferrite cores for easy mounting
- Reduction of parasitic leakage current
- Reduction of cable noise-emission
- Small dimensions and easy installation
- High permeability
- The inductance can be chosen by the number of turns
| File | Size |
|---|---|
| Data_Sheets » EMC » Motor_Chokes | |
| EPA_Ferrite-ring-cores_OC_data-sheet.pdf | 678.26 K |
| Data_Sheets » EMC » Ring_Cores | |
| EPA_Ferrite_rings_OC_Datasheet.pdf | 678.01 K |
CHA
High performance motor chokes
- Current ratings from 10 A up to 200 A
- Common mode output-choke
- Prevents over-current trips on long motor cable
- Attenuates parasitic leakage currents and voltage-reflexions on motor cable
- Protects the motor winding and motor bearings
| File | Size |
|---|---|
| Data_Sheets » EMC » Motor_Chokes | |
| EPA_Motor-chokes_CHA_data-sheet.pdf | 711.59 K |
The above-mentioned filters are generally integrated in the (motor) cable between the inverter output and the motor. They are intended to reduce interference emissions from the motor cables and limit voltage peaks caused by the inverter clock frequency. In addition to improved EMC, the aim is to protect the motor and also to achieve reliable operating behaviour.
Note
An analysis of the whole system (inverter, motor, cables, earthing, environment, etc.) is required in order to achieve an optimum interference suppression effect and to be able to select the appropriate product.
We will be happy to help you with this!
The differences between the individual motor filters are briefly explained in the following text:
dV/dt chokes
These chokes are designed to limit the steep switching edges at the inverter output to a level that is not harmful to the motor. The voltage peaks caused by the fast switching times of the IGBTs (switching frequencies of up to 16 kHz or more) can reach dV/dt values of 12 kV/s in unfavorable cases (according to VDE 0530, 500-1000 V/s are permissible depending on the motor type). This value depends on factors such as the output signal of the inverter, the cable length and routing as well as the cable type.
The short voltage rise times can lead to damage to the motor insulation and thus to premature ageing of the motors. Particular attention must be paid to this with older motor types or motors that are not specially manufactured for inverter operation. In order to protect the connected motors and ensure continuous, safe operation, it is essential to limit these switching edges. The dV/dt choke is preferably used with short motor cable lengths. For longer motor cables, the use of a sine wave output filter is recommended for economic reasons.
Advantages
- Significant reduction of the switching edges (dV/dt)
- Attenuation of interference emissions from the motor cable
- Effective against symmetrical interference
- Low voltage drop
- Less expensive than a sinusoidal filter
Ferrite rings and current-compensated chokes
A ferrite ring is often used to suppress interference in motor or signaling cables. Thanks to its minimal dimensions, it can be easily integrated into the cables. The toroidal cores can also be integrated into existing cable networks with little effort, even at a later date.
The effectiveness depends on the core material (AL value) of the ferrites and the number of windings on the core. If a cable is only fed through the core once, this corresponds to one winding. The more windings, the higher the inductance. It is important to keep in mind that too many windings can cancel out the interference suppression effect of the choke (saturation effects). If necessary, several cores should be connected in series and the cables should only be routed through the toroidal cores a few times.
Ferrite rings are usually used with current-compensated winding in order to suppress asymmetrical interference (so-called common mode interference) on the cables and to attenuate parasitic leakage currents of the cable shields (especially with long motor cables) as well as motor bearing currents.
With a current-compensated winding, the magnetic fields of the low-frequency operating current (usually 50 or 60 Hz) cancel each other out, but it is very effective for the high-frequency interference currents or represents a high resistance for these. When used in motor cables, care must be taken to ensure that the toroidal cores are installed as close as possible to the source of interference (e.g. frequency inverter or servo inverter) and that only the three motor phases (without protective conductor and cable shield) are routed through the core in the same direction, otherwise the attenuation is very low.
Advantages
- Attenuation of interference emissions from the cables
- Reduction of leakage and bearing currents
- Effective against asymmetrical interference
- Inductivity can be selected by the number of windings
- Simple installation and small dimensions
- Also suitable for very long motor cables
- Can prevent overcurrent shutdowns of the inverter
- Reduces interference coupling to the mains supply cable
- Cost-effective