27,5-35KV Single-phase power transformers ОМ, ОМГ type

TECHNICAL CHARACTERISTICS OF THE TRANSFORMERS:
Power line: 2,5; 4,0; 6,3; 10,0 kVA
HV voltage: 35kV; 27,5kV
LV voltage: 0,23kV

Short circuit current: 4,5%

HV adjustment limits: ±2 х 2,5%

ОМ, ОМГ, ОМЖ - type transformers marking structure: 

ОМ, ОМГ, ОМЖ, - XXX/XX Y1:

• О – single-phase transformer.
• М – natural air cooling system with natural oil circulation.
• Г - hermetically sealed transformer (no expansion tank).
• Ж – transformers for railway electric grids (27,5kV HV).
• XXX – transformers rated power , kVA.
• XX – voltage class of high voltage winding (HV), kV.
• У(УХЛ)1 – climatic copmosition У(УХЛ) and accommodation category 1 (ГОСТ 15150-69).

The transformers cas a core with two-rod laminated magnetic system, assembled of cold-rolled electric steel sheets using "Step-Lap" technology. The windings are cylindrical-shape, are placed on core rods concentrically. The tank of a power transformer is equipped by fittings for filling, sampling, filtering and draining of the transformer oil, as well as for connecting a cooling system and vacuum pump. 
Transformers tanks for 16kVA and more are fitted by expansion tank (ОМ) or corrugated cheeks (ОМГ).

Transformers are suitable for indoor and outdoor use and for use in the following conditions:

- altitude up to 1000 m;

- temperate and cold climates - У1 (УХЛ1);
- Operating temperature range: from -45°C (Y1) or -60°C (YHL1) to +40°C
Transformers are not suitable for use in the following conditions:
- In the explosive and corrosive medium (containing gases, vapors, dusts and others in an increased concentration);
- Vibration or shock;
- With frequent on-load reconnections on the feeding side.

The OM transformers are equipped with oil-level indicator, designed to control the oil level in the expansion tank.

The transformers has the ability of HV adjustment, with control range ± 2x2.5% of the rated voltage. Type of control - PBV (switching without excitation). Switching the transformer to another level should be operated in off-load mode.
Upon customers request, accessories can be added or changed.

The design of the transformer
The transformer consists of the following units:
- The transformer tank;
- The active part rigidly attached to the cover;
- Entries;
- Oil conservator;
- Dehumidifier;
- Protective and control devices
Transformer tanks are made with welding connections, has rectangular shape and made of a corrugated cheeks providing volumetric expansion of the oil at different ambient temperatures. The corrugated cheeks are cooling elements (the tanks with radiators can be manufactured on customers request).
The cover is rectangular. HV, LV entries, PBV switch, expander control devices are mounted on the cover.
The active part consists of a core, LV winding, HV winding.
The frame consists of a magnetic core, upper and lower yoke is pulled yoke beams. The three-rod magnetic core is made of cold rolled electrical steel using "Step-lap" blending scheme.
LV and HV windings are made of aluminum wire (copper wire on request).
Since permanent inmrovements involving to our transformers, LV windings can be made of aluminum foil.

Transformers are compliant to TУ 31.1-13608660-062:2007
Transformers made according to ГОСТ 11677, 11920.