External Transformer Options for PXe-C Series SFCs
PX Electronics can supply external transformer options for PXe-C Series Static Frequency Converters where a project requires voltage matching, a specific electrical interface, load voltage adaptation or a multi-pulse input arrangement.
These transformers complement the SFC and do not replace the integrated transformer isolation already provided within the PXe-C Series. They are additional system components selected to solve a specific installation requirement.
Typical applications include adapting 440V or 480V site supplies to a 400V SFC input, providing a required vector group or neutral arrangement, matching a particular load voltage and supporting phase-shifted multi-pulse rectifier configurations.
Important: Additional Transformer Option
PXe-C Series SFCs already include integrated transformer isolation. External transformers are supplied only where the wider installation requires an additional voltage, interface, harmonic or environmental function.
Technical Highlights for External SFC Transformers
Site & Load Voltage Matching
Adapts non-standard site or load voltages to the required PXe-C Series configuration.
Electrical Interface Requirements
Provides project-specific vector groups, neutral arrangements or winding configurations where required.
Multi-Pulse Input Options
Phase-shifting transformers can support suitable multi-pulse SFC rectifier arrangements where improved input harmonic performance is required.
Industrial & Marine Configurations
Enclosure, winding material, cooling and monitoring options can be selected for the installation environment.
Complete SFC System Engineering
PX coordinates transformer position, rating, voltage ratio, earthing, protection and operating duty with the selected SFC and connected load.
Product Information
Matching an External Transformer to a PXe-C Series SFC
An external transformer is specified only where the electrical installation around the converter requires an additional interface.
It does not alter or remove the standard integrated transformer isolation within the PXe-C Series.
PX therefore reviews the complete arrangement, including the site supply, external transformer, SFC input, converter output and connected load.
| Selection Parameter | Information Required |
|---|---|
| Purpose of Transformer | Voltage matching, load interface, vector-group requirement, neutral arrangement, multi-pulse input or other defined system function. |
| Transformer Position | Ahead of the SFC input, after the SFC output or as part of a multi-pulse rectifier arrangement. |
| SFC Rating | Continuous converter kVA together with expected overload and starting-current requirements. |
| Site Supply | Available voltage, frequency, phase arrangement, tolerances and earthing system. |
| Required Secondary Voltage | Voltage required at the SFC input or connected load. |
| Vector Group & Neutral | Required winding connection, neutral provision and phase displacement. |
| Connected Load | Load type, continuous power, power factor and starting or inrush requirements. |
| Environment | Indoor, marine, dusty, humid, high-temperature or other special operating conditions. |
| Enclosure | Open transformer for protected integration or separate enclosed assembly. |
| Cooling | Natural-air, forced-air or other project-specific cooling requirements. |
| Monitoring | Temperature sensors or other transformer condition monitoring where required. |
Transformer Rating
The external transformer should be selected around its actual system duty, rather than simply assigning the same nominal kVA as the SFC without review.
PX considers continuous load, transformer losses, power factor, starting current, SFC overload requirements, ambient temperature, cooling, enclosure, harmonic loading and operating duty.
For example, a 63kVA transformer provides a logical starting point for a 60kVA C-Series voltage-matching application, subject to confirmation of the connected load and operating conditions.
Additional Transformer Options for PXe-C Series SFCs
The appropriate transformer depends on the specific electrical function required around the SFC.
| Transformer Option | Additional Function | Typical PXe-C Series Application |
|---|---|---|
| Voltage-Matching Transformer | Changes the site or load voltage using separate windings | Example: 440V site supply feeding a PXe-C Series configured for 400V input. |
| Voltage-Matching Autotransformer | Compact voltage adaptation without additional galvanic isolation | Suitable where only the voltage needs to be changed and another isolated transformer stage is not required. |
| Interface Transformer | Provides a required vector group, neutral arrangement or electrical interface | Integration with existing plant distribution or equipment requiring a defined winding configuration. |
| Multi-Pulse Transformer | Provides phase-shifted supplies for multiple rectifier bridges | Multi-pulse C-Series input configurations where improved input harmonic performance is required. |
| Special-Environment Transformer | Provides the required electrical interface in construction suited to the installation environment | Marine, humid, dusty, high-temperature or other demanding industrial installations. |
External Voltage-Matching Transformers
A voltage-matching transformer is useful where the available site voltage does not directly match the input voltage selected for the PXe-C Series, or where a particular load requires further voltage adaptation.
Typical arrangements include:
- 440V site supply to 400V SFC input
- 480V site supply to 400V SFC input
- 415V site supply to a project-specific SFC input
- 400V SFC system interfacing with 208V equipment
- 400V SFC system interfacing with 440V or 480V equipment
Where separate primary and secondary windings are used, the external transformer naturally provides another galvanically separated stage. This additional isolation is a feature of the external transformer and is not a substitute for the integrated isolation already provided within the PXe-C Series.
Transformer ratings, winding materials, vector groups, enclosure protection and cooling arrangements can be selected around the actual PXe-C Series installation rather than restricting the system to a small number of standard voltage combinations.
Example: 63kVA 440V to 400V Input Transformer
A practical example is an installation where the available mains supply is 440V, but the selected PXe-C Series converter is configured for 400V input.
The additional transformer is installed ahead of the converter:
440V Site Supply → External 440/400V Transformer → PXe-C Series SFC with Integrated Transformer Isolation → Required Output
An example configuration suitable for this type of application is a 63kVA three-phase 440/400V transformer with Dyn5 connection, 50Hz operation, S1 continuous duty, natural-air cooling, VPI impregnation and an electrostatic shield.
| Parameter | Example Configuration |
|---|---|
| Rated Power | 63kVA |
| Primary Voltage | 440V |
| Secondary Voltage | 400V |
| Phases | Three-phase |
| Connection Group | Dyn5 |
| Frequency | 50Hz |
| Duty | S1 continuous |
| Cooling | AN natural air |
| Impregnation | VPI |
| Winding Material | Aluminium / aluminium |
| Electrostatic Shield | Yes |
| Protection | IP00 |
| Approx. Dimensions | 540 × 375 × 500mm |
| Approx. Weight | 230kg |
| Applied Standard | PN-EN 60076-11 |
In this arrangement, the external transformer performs the 440V to 400V supply adaptation. The PXe-C Series then performs the frequency conversion, output regulation and its normal integrated transformer-isolation function.
External Voltage-Matching Autotransformers
Where the only requirement is voltage adaptation and an additional isolated transformer stage is not required, a three-phase autotransformer can provide a more compact solution.
For example:
480V Site Supply → External 480/400V Autotransformer → 400V PXe-C Series Input
The autotransformer performs only the voltage-matching function. The integrated transformer isolation within the PXe-C Series remains unchanged.
Because an autotransformer has an electrically connected primary and secondary winding arrangement, it does not provide galvanic isolation between its input and output. Its suitability should therefore be assessed against the site’s earthing and electrical distribution arrangement.
Multi-Pulse Input Transformers
For suitable higher-power PXe-C Series systems, a purpose-designed phase-shifting transformer can form part of a multi-pulse rectifier arrangement.
The transformer provides separate phase-shifted secondary supplies to the SFC rectifier stage. This can reduce dominant lower-order input current harmonics compared with a conventional six-pulse rectifier arrangement.
Multi-pulse transformer selection is application-specific. The transformer, rectifier arrangement and SFC input stage should be designed as a coordinated system rather than selecting a general-purpose transformer independently.
Transformer Construction Options
External transformers can be configured around the installation and project requirements.
Enclosure Protection
Open transformers can be supplied for integration within a suitably protected electrical enclosure, while separately enclosed transformer assemblies can be specified for industrial installations.
Options such as IP23, IP44 or IP54 can be considered according to the installation environment and cooling requirements.
Higher enclosure protection should not be selected in isolation from the transformer’s thermal design and required airflow.
Marine and Demanding Environments
Transformer construction can be adapted for marine, humid, dusty, warm or otherwise demanding installations.
Environmental requirements should be identified when the SFC system is specified so that winding insulation, enclosure, cooling and corrosion protection can be considered together.
Copper or Aluminium Windings
Copper or aluminium winding construction can be specified according to the transformer design, dimensions, weight, losses and project requirements.
Temperature Monitoring
Temperature sensors can be incorporated into suitable transformer designs for connection to local indication, alarm circuits or a wider monitoring system.
Cooling
Depending on transformer rating and installation conditions, cooling may use natural-air, forced-air or another project-specific arrangement.
Important Frequency Consideration
50Hz, 60Hz and 400Hz Transformer Applications
The external transformer must be designed for the frequency present at the point where it is installed.
Conventional industrial transformer configurations are normally selected for 50Hz or 60Hz operation.
This is straightforward where the transformer is installed on the mains-input side of a conventional 50Hz or 60Hz PXe-C Series system.
Where an additional transformer is required on an SFC output operating at 400Hz or another non-standard frequency, PX will specify a transformer designed specifically for the required frequency, voltage, current and connected load.
A transformer intended solely for 50/60Hz operation should not automatically be assumed suitable for a 400Hz output.
Ordering Information
Information Required to Specify an External Transformer
| Requirement | Information to Provide |
|---|---|
| SFC Model / Rating | PXe-C model or required converter kVA. |
| Transformer Purpose | Voltage matching, interface requirement, multi-pulse input or other specific function. |
| Primary Voltage | Nominal site or SFC output voltage and tolerance. |
| Secondary Voltage | Required SFC input or connected-load voltage. |
| Frequency | 50Hz, 60Hz, 400Hz or other required operating frequency. |
| Load | Continuous kVA, load type, power factor and starting/inrush characteristics. |
| Electrical Arrangement | Required vector group, neutral and earthing arrangement. |
| Installation | Environment, required enclosure protection, ambient temperature and available space. |
| Monitoring | Temperature sensors or other monitoring requirements. |
Yes.
External transformers can be supplied in enclosed configurations where the installation requires greater protection against dust, contact or water ingress.
The required protection level should be selected together with the transformer cooling and environmental requirements.
Yes, where a particular load voltage or electrical interface requires it.
The transformer must be designed for the SFC output voltage, frequency, waveform, current and connected load.
It is an additional load-interface component and does not replace the integrated transformer isolation within the SFC.
Yes.
A typical example is a 63kVA three-phase transformer with 440V primary, 400V secondary, Dyn5 connection, electrostatic shield and continuous S1 duty.
This type of transformer can be installed ahead of a suitably rated PXe-C Series SFC where the site voltage requires adaptation.
Yes.
A purpose-designed phase-shifting transformer can be supplied as part of a suitable multi-pulse PXe-C Series input configuration.
The transformer and converter input stage are engineered together as a coordinated system.
Not automatically.
A transformer must be designed for the frequency at which it operates. A conventional 50/60Hz transformer should not simply be assumed suitable on a 400Hz SFC output.
Where a transformer is required at 400Hz, PX will confirm a design specifically suited to the required frequency, voltage, current and load.
No.
The external transformer performs a specific interface function outside the converter, such as changing a 440V site supply to 400V.
The PXe-C Series then receives the correctly matched supply and continues to provide its normal frequency conversion, voltage regulation, protection and integrated transformer isolation.
A multi-pulse transformer provides separate phase-shifted AC supplies for multiple rectifier bridges.
When used with a suitable SFC rectifier architecture, this arrangement can reduce dominant lower-order input current harmonics compared with a conventional six-pulse input.
A conventional voltage-matching transformer uses separate primary and secondary windings.
An autotransformer uses an electrically connected winding arrangement and does not provide galvanic separation between its input and output. It can provide a more compact solution where voltage adaptation is the only additional requirement.
Whichever option is selected, the integrated isolation within the PXe-C Series remains unchanged.
The transformer rating depends on its actual duty within the SFC system.
PX considers continuous load, transformer losses, overload requirements, starting current, ambient temperature, enclosure, harmonic content and duty cycle before confirming the transformer rating.
The transformer should therefore not be selected solely by matching its nominal kVA to the SFC nameplate.
PXe-C Series Static Frequency Converters already incorporate transformer isolation as part of the converter design.
An additional external transformer is only used where the wider installation requires another electrical function, such as matching a 440V or 480V site supply to a 400V SFC input, providing a particular winding or neutral arrangement, adapting the load voltage or supporting a multi-pulse input configuration.
The external transformer therefore complements the SFC rather than replacing its integrated transformer isolation.
