SPO-4

SPO-4 static single-phase converter

SPO-4 is an aircraft static single-phase converter that transforms 27 V DC aircraft power into 36 V, 400 Hz single-phase AC of rectangular waveform. The conversion is performed by transistors operating in switching mode. This confirmed electrical purpose places SPO-4 in Power Transducers rather than among generic electronic control units.

Main and standby conversion channels

The published design uses two channels to improve reliability. The main channel includes an oscillator and power amplifier, while the standby channel has its own corresponding stages. An output transformer forms the required supply, a contactor transfers the output circuit to the standby channel, and a monitoring block supports serviceability control.

Output data and connected loads

The documented input is 27 V DC. The output is a rectangular-wave single-phase voltage of 36 ±5 V effective value at 400 Hz ±2%. Maximum output power under the specified active-reactive load is 35 VA. SPO-4 is used to supply individual aircraft instruments, including inductive pressure-gauge transmitters of the DIM family.

Aircraft electrical-system application

Manufacturer information states that SPO-4 is used on many civil aircraft and helicopters. The exact platform and wiring must be confirmed from the aircraft equipment list because the same aircraft electrical system may contain several converter types. Supply voltage, load, mounting and connector configuration must match the installed execution.

Identification, testing and ordering

Inspect the ventilation openings, cables, connectors, mounting feet, fasteners, seals and nameplate. Test both conversion channels, transfer logic, output voltage, frequency and load capability using approved equipment. An enquiry should state SPO-4, aircraft type, required completeness and documentation. Related converters are available under Power Transducers.

Product Name: Static Single-Phase Converter
Primary Designation: SPO-4
Original Cyrillic Designation: СПО-4
Product Type: Aircraft static DC-to-AC converter
Input: 27 V DC
Output Voltage: 36 ±5 V AC, effective value
Output Waveform: Rectangular
Output Frequency: 400 Hz ±2%
Maximum Output Power: 35 VA under the documented active-reactive load
Conversion Method: Transistor switching mode
Reliability Architecture: Main and standby conversion channels
Typical Load: Individual aircraft instruments, including DIM-type inductive pressure transmitters
Aircraft Context: Used on many civil aircraft and helicopters; exact effectivity must be checked
Alternative Designations: SPO-4; SPO4; SPO 4; СПО-4; СПО4
Documentation: Product passport and aircraft electrical-system documentation

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