Description
Used product. Original Schaffner FN258P-75-34 industrial filter, designed for EMC/RFI electromagnetic interference suppression on three-phase systems, particularly for inverters, power converters, and electric drive systems.
The photographed component is clearly identified by the label as FN258P-75-34, Made in Hungary, with a nominal voltage of 3×480/275 V AC, frequency 50–60 Hz, and rated current of 75 A at 50 °C.
The FN258P series consists of two-stage three-phase EMC/RFI filters, developed for applications with inverters and Power Drive Systems. The -34 version uses power terminals, and the chassis construction allows installation directly inside a cabinet or equipment.
⚙️ Technical Specifications
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Manufacturer: Schaffner
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Model: FN258P-75-34
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Series: FN258P
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Type: three-phase EMC/RFI filter
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Configuration: 3-phase / Delta
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Technology: 2-stage filter
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Nominal voltage: 3×480/275 V AC
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Frequency: 50–60 Hz
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Rated current: 75 A @ 50 °C
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Indicative maximum thermal current: approx. 82 A @ 40 °C
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Typical drive power: approx. 37 kW
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Typical leakage current: approx. 0.4 mA for the FN258P version
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Power loss: approx. 24 W
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Mounting: chassis mounting
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Connection: terminal block
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Operating temperature: −25…+100 °C
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Environmental category: 25/100/21
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Visible code/batch: 10 39 R
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Production: Made in Hungary
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Standards/approvals: ENEC, UL, CSA
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Earth connection: present, with PE braid visible in the photographs.
Schaffner documentation confirms for the FN258P-75-34 a current rating of 75 A, typical drive power of 37 kW, power loss of approximately 24 W, and weight of approximately 3.9 kg.
⚡ Function in the Electrical System
The Schaffner FN258P-75-34 is installed on the three-phase power line to attenuate high-frequency interference mainly produced by power electronic stages.
Inverters and converters use fast-switching devices that can generate conducted interference toward the grid. The filter reduces the propagation of these disturbances, contributing to compliance with electromagnetic compatibility (EMC) requirements.
The FN258 series uses a multi-stage structure to achieve high EMI/RFI attenuation and is specifically intended for inverters and power drive systems.
🔌 Connections and Installation
The filter has three power lines:
- L1
- L2
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L3
The photograph clearly shows the LINE marking on the terminals and the PE connection braid.
The label also states the tightening specification “RECOMMENDED TORQUE 4.0–4.5 Nm”, which must be respected for the power connections.
The filter must be connected strictly according to the manufacturer's specified diagram and with correct identification of the LINE/LOAD terminals. Incorrect connection may compromise filter effectiveness and create hazardous electrical conditions.
☀️ Applications
The FN258P-75-34 is particularly suitable for:
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photovoltaic inverters;
- industrial inverters;
- frequency converters;
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Power Drive Systems;
- motor drives;
- power electronic equipment;
- industrial electrical panels;
- three-phase systems requiring EMC/RFI interference reduction.
Schaffner documentation explicitly identifies the FN258 series as an EMC solution for inverters and Power Drive Systems.
🔧 Faults, Errors and Symptoms
A deteriorated or damaged EMC filter may exhibit:
- increased electromagnetic interference;
- conducted disturbances on the power network;
- EMC compatibility problems;
- noise or interference on nearby electronic equipment;
- abnormal heating of the terminals;
- abnormal voltage drop;
- damage to internal components;
- abnormalities caused by loose, oxidized, or overheated connections.
However, an inverter fault must not automatically be attributed to the filter: the grid, wiring, inverter, motor/converter, and grounding system must also be checked.
🛠️ Inspection and Verification
For professional verification of the FN258P-75-34, it is advisable to check:
- enclosure integrity;
- condition of the L1/L2/L3 terminals;
- condition of the PE braid;
- connection tightness;
- possible oxidation;
- signs of overheating;
- continuity of the electrical paths;
- insulation to earth;
- any abnormal voltage drop;
- filter behavior during a controlled test.
The filter should not be checked only by means of a continuity test: insulation, connections, and electrical behavior under appropriate operating conditions must also be evaluated.
🏭 Construction and Product Condition
The photographed component is used and shows normal signs of previous installation and handling, with scratches and slight superficial traces of use on the metal enclosure.
The structure appears intact in the photographs. The three power terminals, PE braid, and chassis mounting system are present.
🌐 Compatibility and Replacement
The FN258P-75-34 is a specific component of the Schaffner FN258 series. For correct replacement, at least the following must be verified:
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75 A rated current;
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3×480/275 V AC;
- three-phase configuration;
- number of stages;
- mechanical dimensions;
- terminal arrangement;
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PE connection;
- EMC characteristics required by the equipment.
The FN258P-75-34 is currently considered obsolete/discontinued by some distributors; replacement components from the newer FN3288 family are available, but they must not automatically be considered equivalent without verifying the application.
🛡️ Safety
The filter operates on a three-phase network up to 480 V AC and with a rated current of 75 A.
Installation, disconnection, and testing must only be carried out by qualified personnel, with the equipment completely disconnected from the power supply and secured.
Particular attention must be paid to the PE connection, correct phase sequence, and terminal tightening according to the manufacturer's specified torque of 4.0–4.5 Nm.
📦 Package Contents
1 × Schaffner FN258P-75-34 three-phase EMC/RFI filter, 3×480/275 V AC – 75 A @50 °C, with power terminals and PE connection, as shown in the photographs.
🚀 Final Description
The Schaffner FN258P-75-34 is a 75 A two-stage three-phase EMC/RFI filter, designed to reduce electromagnetic interference in inverters, converters, and industrial drive systems.
The component operates at 3×480/275 V AC, 50–60 Hz, with a rated current of 75 A at 50 °C, typical drive power of approximately 37 kW, dimensions of approximately 329 × 80 × 220 mm, and weight of approximately 3.9 kg.
The photographed code FN258P-75-34 is clearly legible and identifies a professional version of the FN258P series, now obsolete, making it particularly interesting as an original replacement for industrial equipment and inverters still in service.
