DMR-200VU

DMR-200VU relay for aircraft DC power systems

The DMR-200VU is a differential minimum relay used in aircraft DC power supply systems. Unlike the DMR-200D type, which is usually associated with DC generator circuits, the DMR-200VU is used with rectifier units. These rectifiers convert AC power into DC power for the onboard network. The relay controls when the rectifier is connected to the DC bus and disconnects it when the source can no longer operate safely. In aircraft documentation, the unit is normally treated as part of the secondary electrical power supply system.

DMR-200VU control of rectifier connection

In operation, the relay connects the rectifier unit to the onboard DC network after the required voltage condition is reached. It also disconnects the source when the voltage drops below the allowed level or when the circuit condition becomes unsafe. The relay therefore works as an automatic switching and protection element between the rectifier output and the aircraft DC bus. The crew does not manually manage every switching event. The relay follows the electrical condition of the source and the network.

Protection logic inside the DMR-200VU unit

The DMR-200VU protects the DC network against reverse current, incorrect polarity, and short circuit conditions in the connected rectifier or feeder line. If reverse current appears, the relay opens the circuit and prevents the onboard network from feeding back into the failed source. It can also block connection when polarity is wrong. In service, these functions are important because rectifier faults, feeder faults, and bus faults can look similar from the cockpit indication. Troubleshooting is usually done through the aircraft electrical diagram, not by replacing the relay first.

Rectifier system operation with DMR-200VU

The relay works together with rectifier units, DC busbars, feeder lines, contactor circuits, cockpit switches, warning lamps, and load circuits. It is known from aircraft electrical systems where AC power is converted to DC power through rectifier equipment. One typical application mentioned for this type of relay is the Mi-26 helicopter, where DC supply and protection circuits are part of a larger onboard power system. The exact installation must still be checked by the aircraft parts catalog and wiring documentation.

Identification and ordering checks for DMR-200VU

Before ordering, the marking on the installed relay should be compared with the aircraft documentation, electrical system diagram, or acceptance label. The designation DMR-200VU refers to a relay intended for use with rectifier units, so it should not be treated as a direct substitute for DMR-200D without documentation confirmation. A request should include the aircraft type, rectifier unit type, installation position, and, if possible, a photo of the data plate. The product is also known under alternative designation ДМР-200ВУ.

Product Type: Differential minimum relay for rectifier unit circuits
Function: Automatic rectifier connection, reverse current protection, polarity protection, short circuit protection
Application / Where Used: Aircraft DC electrical power supply systems
System / Installation Area: Secondary power supply system / rectifier output and DC bus protection circuit
Compatible Aircraft / Equipment: Aircraft using rectifier units in DC power supply systems, including Mi-26-type installations
Nominal Voltage: 28.5 V DC
Nominal Current: 200 A
Reverse Current Trip Threshold: 15–50 A
Current Consumption in ON State: Approx. 0.58 A
Connection Actuation Voltage: Not more than 24 V, with no voltage in the network
Disconnection Actuation Voltage: Not more than 9.5 V
Main Components: Two polarized relays UPR1 and UPR2; power contactor K1
Technical Documentation: Aircraft electrical system documentation / acceptance documentation

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