PT-125Ts-4S

PT-125Ts-4S converter for aircraft AC power

The PT-125Ts-4S is an aircraft rotary converter used to obtain three-phase alternating current from the aircraft DC network. In simple terms, it takes power from the 27 V DC bus and produces a 36 V, 400 Hz three-phase output for onboard equipment that cannot operate directly from DC power. This type of converter is used on aircraft where certain instruments and systems require a stable AC supply, including cases when the main AC generators are not available or when backup power from batteries is needed.

PT-125Ts-4S in backup instrument power circuits

One of the important roles of the PT-125Ts-4S is power supply for flight and navigation instruments during abnormal electrical system conditions. When the aircraft loses normal AC generation, the converter can keep selected consumers powered from the DC battery bus. This is especially relevant for instruments such as attitude indicators and related pilotage equipment that require three-phase 400 Hz power. In this role, the converter is not just a general electrical accessory; it is part of the backup power logic that helps preserve essential cockpit information.

Three-phase output of the PT-125Ts-4S

The PT-125Ts-4S produces three-phase AC power with a star connection. The output parameters are intended for equipment designed for low-voltage aircraft AC supply. The converter’s nominal power is enough for selected instrument loads, not for high-power consumers. During operation, the connected load must remain within the permitted current and power limits. If the converter is overloaded, installed in the wrong circuit, or used with unsuitable equipment, voltage stability and frequency quality may be affected, which can lead to unreliable operation of sensitive flight instruments.

Electromechanical design of PT-125Ts-4S

The PT-125Ts-4S is an electromechanical converter, also known as a rotary converter or umformer. Its operation is based on a DC motor section mechanically coupled with an AC generator section. The rotor operates at high speed, which allows the unit to generate the required 400 Hz output. This design is older than modern static converters, but it remains common in aircraft originally built with electromechanical power-conversion architecture. For maintenance, both electrical and mechanical condition matter: bearings, rotor rotation, commutator condition, insulation, vibration, and output parameters should all be checked.

Aircraft application of the PT-125Ts-4S unit

The PT-125Ts-4S is used on Soviet and Russian-designed passenger, transport, military, and special-purpose aircraft. It is associated with platforms such as Il-62M, Il-76, Il-78, Tu-134, Yak-40, An-22, An-24, An-26, An-30, and Mi-24 helicopters, depending on aircraft configuration. On these aircraft, the converter may supply flight-navigation instruments and other low-power AC consumers. Exact applicability should always be checked against the aircraft parts catalog and electrical system documentation, because the same aircraft family may have different equipment sets and modification standards.

PT-125Ts-4S maintenance and replacement

When replacing or ordering the PT-125Ts-4S, the full designation should be checked carefully. Aircraft rotary converters can be similar in appearance but differ in output voltage, power rating, current, phase layout, mounting points, or connector arrangement. Before installation, the unit should be inspected for mechanical damage, free rotor rotation, connector condition, signs of overheating, storage condition, and availability of documentation. In aircraft service, performance verification normally includes input current, output voltage, output frequency, operation under load, noise, vibration, and heating during continuous operation.

Supply and documentation for PT-125Ts-4S

The PT-125Ts-4S may be supplied as new production, from storage, repaired, or overhauled depending on availability. For aviation use, the buyer should confirm passport availability, acceptance records, storage history, and test results where applicable. If the unit is intended for installation on an aircraft, documentation is not a formality: it helps confirm the part number, production or repair status, and suitability for the required system. For export or maintenance supply, it is also useful to specify whether the request is for a single unit, a tested unit, or a unit with recent bench-check documentation.

Product Type: Aircraft electromechanical rotary converter / umformer
Designation: PT-125Ts-4S
Function: Conversion of aircraft DC power into three-phase AC power
Application / Where Used: Aircraft electrical power systems; flight and navigation instrument power circuits
System / Installation Area: Backup / auxiliary AC power supply circuits
Typical Powered Equipment: Flight-navigation instruments, including AGB-3K-type attitude indicators depending on aircraft configuration
Compatible Aircraft / Equipment: Il-62M, Il-76, Il-78, Tu-134, Yak-40, An-22, An-24, An-26, An-30, Mi-24 depending on modification
Input Voltage: 27 V DC
Input Current: Not more than 8.3 A
Output Voltage: 36 V AC
Number of Output Phases: 3
Output Circuit: Star connection
Output Frequency: 400 Hz
Rated Power: 125 VA
Load Current: Up to 2 A
Rotor Speed: 12,000 rpm
Operating Mode: Continuous operation
Dimensions: 250 × 140 × 165 mm
Weight: Not more than 5.5 kg
Technical Documentation: Product passport, acceptance documentation, and aircraft electrical system documentation as applicable

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Warranty
All products are covered by a standard 6-month warranty.
Extended warranty is available upon request and is agreed individually; it may affect the final product price.