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We offer a comprehensive portfolio including resistors, braking units, reactors, power filters, and transformers, with full customization options to meet diverse application requirements.
A Power Supply Filter is installed between the incoming power source and the equipment power input. Its main purpose is to control electromagnetic interference (EMI) conducted through the power line.
Power electronic equipment such as inverters, servo drives, and switching power supplies can generate high-frequency noise during switching operation. External electrical equipment and the power network can also introduce unwanted high-frequency disturbances into the same supply line.
The filter provides impedance to these unwanted high-frequency components while allowing the normal power supply to pass through.
It is designed to work in both directions:
- Reduce high-frequency interference generated by the equipment and conducted toward the power network
- Reduce external RF and electrical disturbances entering the equipment through the supply line
- Suppress common-mode and differential-mode interference
- Reduce the possibility of interference between adjacent electronic equipment
The filter is therefore used as part of the equipment's EMI/EMC control and power-line interference suppression system.
The filter uses a combination of common-mode chokes, X capacitors, Y capacitors, and resistive components to form a low-pass filtering network.
The common-mode choke presents high impedance to common-mode high-frequency noise while allowing the normal supply current to pass.
The X capacitor is connected across the power conductors and provides a path for differential-mode high-frequency noise.
Y capacitors provide a controlled path between the power conductors and ground or chassis reference for appropriate common-mode interference.
Depending on the circuit configuration, resistive components can be used for capacitor discharge and circuit damping.
The combined circuit provides suppression of common-mode and differential-mode interference over the specified frequency range.
The filter can use either a single-stage or two-stage structure.
Single-stage filtering is suitable for applications where the interference level can be controlled with one filtering section and installation space is limited.
Two-stage filtering provides additional attenuation where the equipment operates in a more demanding electromagnetic environment.
The appropriate configuration should be determined according to the equipment, interference characteristics, required attenuation, and installation conditions.
The following specifications apply to the relevant product configuration. Different Dufew Electric filter series may have different voltage and current ranges.
| Parameter | Specification |
|---|---|
| Rated Voltage | 250VAC for the specified single-phase configuration |
| Rated Current | 1A--60A for the specified single-phase configuration |
| Operating Frequency | 50Hz / 60Hz / up to 500Hz, depending on configuration |
| Filtering Range | 5 kHz--30 MHz |
| Dielectric Strength, Line to Line | 1500VDC / 60s |
| Dielectric Strength, Line to Ground | 2250VDC / 60s* |
| Insulation Resistance | >100MΩ at 1000VDC |
| Overload Capability | 1.4 × rated current for 1 minute, with at least 15 minutes between overload events |
| Protection Grade | IP00 / IP20 |
| Insulation Class | T40 / F (155°C) |
| Flame Retardant Grade | UL94V-2 |
| Product Standard | GB/T 15287/8 |
* The supplied technical information also lists 2500VDC / 60s for line-to-ground dielectric strength. The applicable value should be confirmed from the final specification for the selected model.
A typical model designation is: CAF-4 3 1-0010
| Code | Description |
|---|---|
| CAF | Dufew Electric filter series |
| 4 | Voltage class; 2 = 220V, 4 = 380V, 6 = 690V |
| 3 | Phase configuration; 3 = three-phase, 1 = single-phase |
| 1 | Filter category; 1 = input filter, 2 = output filter |
| 0010 | Rated current; 0010 = 10A |
The model designation should be checked against the applicable product specification and nameplate before ordering.
The filter circuit addresses both common-mode and differential-mode high-frequency interference, allowing it to be used where different types of conducted EMI may be present.
The filter can reduce interference generated by the connected equipment and conducted toward the supply network, while also limiting external high-frequency disturbances entering through the power connection.
The specified filtering range covers high-frequency interference associated with switching power electronics and other electronic equipment.
The filtering structure can be selected according to the interference level and installation requirements.
The integrated construction is suitable for installation inside control cabinets and electrical enclosures where mounting space is limited.
The filter is designed for single-phase power electronic equipment where conducted EMI needs to be controlled. It can be used in single-phase inverters, servo drives, switching power supplies, controllers, embroidery machines, engraving machines, industrial control equipment, and other electronic equipment installed in EMI-sensitive environments.
The filter can also be used in electrical installations where multiple electronic devices operate on the same power network and conducted interference may affect equipment operation or system performance.
A filter may be appropriate when equipment experiences interference-related symptoms such as:
- Unexpected shutdowns
- False triggering or abnormal operation
- Communication or control interference
- Excessive electrical noise
- Power-line interference between adjacent equipment
These symptoms can have multiple causes. Before selecting a filter, the actual source of the problem should be identified. A filter does not replace corrective measures for overload, incorrect grounding, insulation failure, equipment faults, or other underlying electrical problems.
Filter selection should consider the equipment's supply voltage, rated current, operating frequency, single-phase configuration, required filtering performance, installation dimensions, grounding method, ambient temperature, and protection level.
For the specified single-phase configuration, the recommended filter rating is approximately 1.2–1.5 times the equipment's rated current. Final selection should also consider actual load current, overload conditions, operating temperature, and the manufacturer's specifications.
For model selection, customers can provide the equipment model, supply voltage, rated current, operating frequency, wiring diagram, installation dimensions, interference symptoms, and operating environment.
Correct installation is particularly important for high-frequency EMI suppression.
Check the equipment voltage and current before installation. The selected filter must be compatible with the equipment supply and operating current.
Check the housing, terminals, mounting points, identification label, and wiring markings. Do not install a damaged unit.
Install the filter as close as practical to the protected equipment's power entry. For cabinet installations, the filter can be mounted on a suitable metal mounting surface according to the installation requirements.
Connect the filter between the incoming power supply and the equipment input according to the applicable wiring diagram. Follow the marked input and output terminals where a defined connection direction is specified.
The grounding terminal must be reliably connected.
Do not bundle the filter input wires and output wires together.
High-frequency interference can couple between closely routed input and output conductors and bypass the filtering circuit. Input-side and load-side wiring should therefore be routed separately and kept apart as far as practical.
The grounding conductor should be short and have sufficiently low impedance for the installation.
After checking the wiring and grounding:
1. Confirm all terminal connections.
2. Check input/output cable separation.
3. Energize the equipment.
4. Observe operating status and alarm conditions.
5. Verify whether the original interference has been reduced.
For compact single-phase equipment, an integrated filter assembly can reduce the number of components required for installation.
| Comparison | Integrated Single-Phase Filter | Separate Filter Units |
|---|---|---|
| Structure | One integrated assembly | Multiple independent assemblies |
| Installation | One filter installation point | Separate units and mounting points |
| Wiring | Dedicated filter input and output terminals | Additional interconnection and routing |
| Cabinet space | Suitable for compact control cabinets | Requires space for each unit |
| Component management | One product assembly | Separate components and accessories |
Actual EMI performance depends on the filter circuit, electrical conditions, grounding, cable routing, and installation quality. The integrated structure itself should not be treated as a guarantee of superior EMI attenuation without application-specific test data.
Dufew Electric manufactures power electronics components including resistors, braking systems, reactors, filters, transformers, and customized electrical components.
For power supply filters, production and inspection can include:
Component Inspection → Filter Assembly → Electrical Testing → Final Inspection → Packaging
Depending on the product configuration, inspection may include:
- Component specification verification
- Terminal and connection inspection
- Insulation resistance testing
- Dielectric strength testing
- Electrical performance testing
- Dimensional inspection
- Final product inspection
Applicable technical records and test documentation can be provided according to product and project requirements.
Dufew Electric has ISO and CE certifications supporting its quality management and product compliance activities.
Applicable certificates and technical documents should be confirmed according to the selected model, product configuration, and intended market.
International orders can be arranged according to product quantity, dimensions, destination, and delivery requirements.
Sea freight, air freight, express delivery, or a customer-nominated forwarder can be used as appropriate. Packaging is selected according to the product structure and transportation conditions.
It is installed at the power input of electronic equipment to suppress conducted electromagnetic interference traveling through the power line. Typical applications include single-phase inverters, servo drives, switching power supplies, and controllers.
The filter is designed to address both common-mode and differential-mode high-frequency interference. The specified filtering range is 5 kHz--30 MHz for the applicable configuration.
It should be installed as close as practical to the protected equipment's power input. Input-side and output-side cables should be separated to reduce electromagnetic coupling that could bypass the filter.
Yes. It is intended for applications including single-phase inverters, servo drives, switching power supplies, controllers, and similar electronic equipment, provided the electrical ratings are compatible.
Selection should consider the equipment's rated and actual operating current, supply voltage, operating conditions, and filter specification. The supplied selection guidance recommends approximately 1.2--1.5 times the equipment's rated current.
It can help when these symptoms are caused or aggravated by conducted electromagnetic interference or power-line disturbances. If the fault results from overload, incorrect grounding, insulation problems, or an internal equipment fault, the underlying cause must be addressed separately.
Electrical ratings, filtering structure, installation dimensions, and other specifications can be evaluated according to the equipment and application requirements.
Yes. Above 1,000 m, reduced heat dissipation may require current derating. The supplied technical information specifies a maximum altitude of 2,000 m and recommends 15% current derating above 1,000 m. The final requirement should be confirmed for the selected model.
Dufew Electric supplies power supply filters for single-phase inverters, servo drives, switching power supplies, controllers, and other power electronic equipment. The filters use common-mode and differential-mode filtering components to reduce conducted EMI through the power connection.
For product selection, provide the equipment voltage, rated current, operating frequency, installation conditions, and available interference information for configuration review.
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No. 364, Kangyang Road, Huangdai Town, Xiangcheng District, Suzhou City, Jiangsu Province, China
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