PTS-25M

PTS-25M static converter in aircraft power systems

The PTS-25M is an aircraft three-phase static converter used to supply onboard equipment that requires alternating current from a DC aircraft power network. The unit converts 27 V DC into three-phase 36 V AC at 400 Hz, which is a standard power format for many aircraft instruments, sensors and control units. In the aircraft electrical system, PTS-25M works as a local power source for equipment that cannot be powered directly from the DC bus. It is a compact converter intended for continuous operation in onboard conditions.

Power conversion function of the PTS-25M

The main task of the PTS-25M is to provide stable three-phase AC output for aircraft consumers. Many onboard systems use low-power three-phase 400 Hz supply for reference, control or instrument circuits. If the aircraft has only a 27 V DC source available in that section of the system, a converter is required. PTS-25M performs this conversion without rotating machinery, which makes it different from older electromechanical converters. The output is sinusoidal and intended for equipment that requires a clean and predictable AC supply.

PTS-25M on Mi-8, Mi-17 and Ka-32 aircraft

The PTS-25M can be used on helicopters such as Mi-8, Mi-17 and Ka-32, depending on the aircraft configuration and installed equipment. In these applications, the converter may feed individual instruments, control units, small avionics circuits or other low-power consumers requiring 36 V three-phase AC. The exact installation must always be checked by aircraft parts catalog and wiring documentation. Similar converters can differ by output voltage, phase configuration, power rating, mounting frame and connector layout, so replacement by name alone is not enough.

Static design of the PTS-25M converter

The PTS-25M is a static semiconductor converter, meaning it has no rotating electrical machine inside. This gives several practical advantages: lower noise, less mechanical wear and a more compact installation compared with motor-generator type converters. The unit includes electronic control circuits, inverters, a master oscillator, output shaping elements and radio-interference filters. This internal structure allows the converter to form the required AC output from the DC input. In service, attention is normally paid to the electronic condition, cooling, connector state and stability of the output voltage and frequency.

Cooling and mounting of the PTS-25M

The converter is installed on a special shock-absorbing mounting frame to reduce vibration loads from the aircraft structure. Inside the housing, a built-in electric fan is used for cooling. This is important because even a low-power static converter produces heat during continuous operation, especially when working close to rated load or in warm ambient conditions. If airflow is blocked, the converter can overheat or become unstable. During maintenance, the frame, shock absorbers, fan operation, housing ventilation, connector condition and signs of overheating should be checked carefully.

Protection and overload capability of PTS-25M

The PTS-25M is designed for continuous operation and can withstand short-term overloads within the limits specified for the unit. It also includes short-circuit protection, which is important in aircraft power circuits where a downstream fault must not immediately damage the converter or create a wider electrical problem. The overload capability is intended for temporary operating conditions, not for long-term operation above rated load. When troubleshooting, it is important to check not only the converter itself, but also the connected consumer, wiring, insulation condition and possible short circuits in the output circuit.

Identification and supply of PTS-25M

For procurement or replacement, the converter should be identified by the full designation PTS-25M. It is also important to specify whether the unit is required with its mounting frame, shock absorbers, connector set or only as a standalone converter. Before installation, the technical condition, storage history, documentation, output parameters and cooling fan operation should be verified. The unit may be supplied as new, stored, repaired or overhauled depending on availability and documentation. For aircraft use, passport and test documentation should be checked before shipment.

Product Type: Aircraft three-phase static converter
Designation: PTS-25M
Function: Conversion of 27 V DC aircraft power into three-phase 36 V AC, 400 Hz
Application / Where Used: Aircraft electrical power supply systems and onboard equipment power circuits
System / Installation Area: Aircraft DC-to-AC conversion circuit; avionics and instrument power supply lines
Compatible Aircraft / Equipment: Mi-8, Mi-17, Ka-32 and other aircraft depending on installed equipment and approved documentation
Input Voltage: 27 V DC
Maximum Input Current: 1.6 A
Output Voltage: 36 V three-phase AC
Additional Output Channel: 5.5 V single-phase AC
Output Frequency: 400 Hz
Rated Power: 25 VA
Output Waveform: Sinusoidal
Operating Mode: Continuous operation
Design Type: Static semiconductor converter
Internal Components: Control units, inverters, master oscillator, radio-interference filters, built-in electric cooling fan
Cooling: Built-in electric fan
Mounting: Shock-absorbing mounting frame
Overload Capability: Short-term 5-minute current overload up to 25% above nominal
Protection: Short-circuit protection
Technical Documentation: Product passport, test documentation and aircraft maintenance documentation as applicable

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