PXe-ACOS Automatic Changeover Switch
DSP-Controlled Static Transfer Between Independent AC Sources
The PXe-ACOS Automatic Changeover Switch provides fast, automatic transfer of an electrical load between two independent AC power sources. It is intended for applications where continuity of supply is important, and a loss or abnormal condition on the normal source should initiate transfer to an available alternative source.
The DSP-controlled static switching system continuously monitors the normal and alternate supplies. When the active source moves outside the permitted operating limits, the ACOS checks the alternative source and transfers the load when suitable conditions are confirmed.
PXe-ACOS systems can be configured for single-phase or three-phase power at 50Hz, 60Hz or 400Hz. Typical arrangements include Static Frequency Converter bypass, primary and standby SFC systems, dual 400Hz aircraft power sources and changeover between independent industrial AC supplies.
Technical Highlights
Fast Static Changeover
DSP-controlled solid-state switching provides a published transfer time of less than 30ms in synchronised mode, with faster changeover possible depending on the connected load and project requirements.
Multiple Source Configuration & Priority Control
Two independent AC sources are standard, with a three-input configuration available as an option. Automatic or manual operation can be selected, including priority normal source and priority alternate source modes.
50Hz, 60Hz & 400Hz Operation
Suitable for standard industrial supplies, Static Frequency Converter systems and specialist 400Hz aviation or defence power applications.
Source Monitoring & Output Protection
Monitors overvoltage, undervoltage, phase failure and incorrect phase sequence before connecting a source to the load, with protection against output overvoltage, undervoltage, overload, short circuit and overtemperature.
Local & Remote Monitoring
Front-panel indication shows source availability, active output and operating mode, with optional RS232, RS485, USB and LAN interfaces for remote monitoring and source-priority control.
Product Information
Source and Changeover Configuration
The PXe-ACOS is configured around the two available AC sources, connected load, nominal voltage, frequency, phase arrangement and required changeover performance.
Two input sources are standard. A three-source arrangement can be supplied where an additional alternative supply is required.
Available Configurations
| Parameter | Available Configuration |
|---|---|
| Source Inputs | Two independent AC sources as standard; three-source configuration optional |
| Phase Arrangement | Single-phase or three-phase |
| Nominal Voltage | 110V, 230V or 415V AC; alternative project-specific voltages subject to review |
| Frequency | 50Hz, 60Hz or 400Hz |
| Transfer Technology | DSP-controlled static switching |
| Changeover Time | Less than 30ms in synchronised mode; faster options may be available depending on the load |
| Operating Selection | Automatic, normal source, alternate source and manual maintenance selection |
| Protection Devices | MCCBs for normal source input, alternate source input and output |
| Communication | Optional RS232, RS485, USB or LAN interfaces |
| Construction | Standard enclosed system or optional 19-inch rack-mount construction |
| Enclosure Protection | IP42 standard; alternative IP ratings available |
Common ACOS Arrangements
| Arrangement | Normal Source | Alternate Source |
|---|---|---|
| SFC Bypass | Static Frequency Converter output | Compatible alternative AC supply |
| Duty and Standby SFC | Primary Static Frequency Converter | Standby Static Frequency Converter |
| Dual 400Hz Power | Primary 400Hz AC source | Alternative compatible 400Hz source |
| Independent AC Sources | Preferred utility, generator or conditioned AC source | Compatible standby supply |
The less-than-30ms transfer figure applies in synchronised mode. Where the sources are not sufficiently aligned in voltage, frequency or phase, the permitted transfer sequence and resulting interruption must be confirmed for the project.
Specifying a PXe-ACOS System
The ACOS must be selected around both sources and the complete electrical behaviour of the connected load.
Information Required
| Requirement | Information to Provide |
|---|---|
| Normal Source | Voltage, frequency, phase arrangement, capacity and source type |
| Alternate Source | Voltage, frequency, phase arrangement, capacity and source type |
| Connected Load | Continuous current or kVA, load type, power factor, inrush current and overload requirement |
| Transfer Requirement | Maximum permitted interruption and whether the sources normally operate in synchronism |
| Source Priority | Normal preferred source, alternate preferred source or automatic availability-based selection |
| Source Limits | Permitted voltage, frequency, phase sequence and synchronisation limits |
| Manual Controls | Automatic, normal source, alternate source and maintenance selection requirements |
| Communication | RS232, RS485, USB, LAN, remote monitoring or priority-selection requirements |
| Installation | Enclosure format, rack mounting, IP rating, cable entry, shock protection and environmental conditions |
| Compliance | IEC, EMI/EMC, defence or project-specific compliance requirements |
Available Options
Three-Source Configuration
A third independent AC source can be incorporated where the installation requires an additional standby supply.
Faster Changeover
A faster transfer option may be available depending on the load, source conditions and required transfer performance.
RS232, RS485, USB or LAN Interface
Optional communication interfaces allow remote monitoring and source-priority selection.
19-Inch Rack-Mount Construction
Rack-mounted construction is available for installations where the ACOS must be integrated into a wider equipment rack or control system.
Alternative Enclosure Protection
IP ratings other than the standard IP42 can be supplied where required by the installation environment.
MIL-Grade Construction
Project-specific construction can include MIL-grade connectors, suitable shock mounts, EMI filters, EMI gaskets and enclosure heaters.
Defence EMI/EMC Options
The source brochure identifies JSS 55555 N1 and MIL-STD-461E/F configurations. These should be specified as optional project requirements and confirmed against the final supplied system.
Local Manual Selection
A key-operated manual and maintenance changeover selector allows authorised selection of automatic, normal or alternate source operation.
Input and Output MCCBs
MCCBs are provided for the normal source, alternate source and output. Device ratings are selected to suit the project current and protection requirements.
Factory Acceptance Testing
Testing can include source failure simulation, input protection checks, source-priority operation, manual selection, alarm verification and changeover timing.
PXe-ACOS Technical Specification
| Specification | PXe-ACOS Series |
|---|---|
| Type | Static transfer switch, DSP controlled |
| Reference Standard | IEC 62040-3 |
| Standard Configuration | Two input sources |
| Optional Configuration | Three input sources |
| Input and Output Voltage | 110V, 230V or 415V AC, single-phase or three-phase |
| Nominal Frequency | 50Hz, 60Hz or 400Hz |
| Voltage Regulation | ±1% with respect to the input |
| Changeover Time | Less than 30ms in synchronised mode |
| Faster Changeover | Optional, depending on the connected load |
| Overload Capability | 110% for 10 minutes; 125% for 1 minute |
| Priority Selection | Automatic, normal source or alternate source selection using a front-panel rotary switch |
| Manual and Maintenance Selection | Key-operated automatic, normal or alternate source selection |
| Circuit Protection | MCCBs for normal source input, alternate source input and output |
| Input Protection | Input overvoltage, undervoltage, phase failure and incorrect phase sequence |
| Output Protection | Output overvoltage, undervoltage, overload, short circuit and overtemperature |
| LCD Indications | Normal source R/Y/B available; alternate source R/Y/B available; output R/Y/B on; automatic, normal priority, alternate priority, overload and manual bypass status |
| User Interfaces | Optional RS232, RS485, USB or LAN for monitoring and priority selection |
| Standard Enclosure | IP42 |
| Alternative Enclosures | Alternative IP ratings available as options |
| Operating Temperature | -10°C to 55°C maximum |
| Storage Temperature | -10°C to 70°C maximum |
| Relative Humidity | Up to 95% RH, non-condensing |
| Maximum Altitude | 1,000 metres; derating required above 1,000 metres |
| Rack-Mount Option | 19-inch rack-mount construction available on request |
| MIL-Grade Options | JSS 55555 N1 and MIL-STD-461E/F project configurations, subject to confirmation |
Important: The published changeover time applies in synchronised mode. Final changeover performance must be confirmed against the two sources and the ride-through capability of the connected load.
Manual and automatic source selection are provided locally. Optional RS232, RS485, USB and LAN interfaces can be supplied for remote monitoring and priority selection.
To prepare a quotation, PX Electronics will require the voltage, frequency and phase arrangement of both sources, load current or kVA, load type, transfer-time requirement, source priority, control requirements, enclosure arrangement and any applicable compliance requirements.
Yes, provided the alternative source has the correct voltage, frequency, phase arrangement and capacity for the connected load.
For example, equipment requiring 400Hz cannot be bypassed directly to a standard 50Hz mains supply.
Yes. The PXe-ACOS can be configured for 50Hz, 60Hz or 400Hz applications, including aircraft, avionics and defence power systems.
Both sources must be electrically compatible with the connected 400Hz load.
Fast transfer requires the sources to operate within the agreed voltage, frequency and phase limits.
Where the sources are not sufficiently synchronised, the transfer may be delayed, inhibited or completed using a longer break-before-make sequence.
The published changeover time is less than 30ms in synchronised mode.
Faster transfer may be available depending on the connected load, source conditions and selected system configuration.
The transfer is designed to minimise disruption to the connected equipment, but less than 30ms still represents a brief interruption.
The load should be checked to confirm that it can tolerate the specified transfer time.
An automatic changeover switch transfers a connected load between two independent AC sources when the active source fails or moves outside its permitted operating limits.
A mechanical changeover switch normally uses contactors or motor-operated switching devices. Its transfer time is partly determined by the physical movement of those components.
The PXe-ACOS uses DSP-controlled solid-state switching, allowing faster transfer where the sources and connected load are suitable.
The PXe-ACOS can be used for Static Frequency Converter bypass, duty and standby SFC selection, dual 400Hz power sources and automatic transfer between compatible utility, generator or conditioned AC supplies.
The PXe-ACOS monitors input overvoltage, undervoltage, phase failure and incorrect phase sequence.
Output protection includes overvoltage, undervoltage, overload, short circuit and overtemperature. MCCBs are provided for the normal source, alternate source and output.
