TMG-400 400 kVA 10/0.4 kV transformer (S13-M-400)

TMG-400 (S13-M-400) technical data

Rated current and permissible load

Losses, efficiency and comparison with amorphous SH15

The amorphous-alloy core of the SH15 cuts the no-load loss by 51 % compared with the S13. For one 400 kVA transformer this saves about 1840 kWh per year, because no-load loss is present the whole time the transformer is energised, regardless of the load.

Where a 400 kVA transformer is used

400 kVA is a commonly requested rating for medium-sized loads. Typically, the TMG-400 is installed in substations serving residential complexes and multi-storey housing, supermarkets and smaller shopping centres, and small and medium factories, workshops and warehouses. At this size one unit usually covers the lighting, lifts, pumps, ventilation and refrigeration of a single site. The hermetically sealed corrugated tank with vacuum oil filling allows the transformer to be placed both in indoor substations and in outdoor compact substations.

• Residential complexes and multi-storey housing
• Supermarkets and shopping centres
• Small and medium manufacturing plants
• Warehouses, including cold storage
• Hotels, offices and administrative buildings
• Pad-mounted and prefabricated compact substations

How to choose a TMG-400

Size the transformer on the calculated maximum demand after applying a diversity factor. A continuous loading of 70–80% is a sound target for an oil-immersed unit: for the TMG-400 that is 252–288 kW at cos φ 0.9, against 360 kW at full load. If the demand with margin fits within 250 kVA and no growth is planned, the TMG-250 with its lower no-load loss is the leaner choice. If the load is already close to 288 kW, or a second construction phase or a new production line is planned, move up to the TMG-630 or design a substation with two TMG-400 units for redundancy.

The TMG-400 is built with vector group Yyn0 or Dyn11. Dyn11 copes better with unbalanced single-phase loads and with third harmonics from LED lighting, UPS systems and IT equipment, and it gives a larger single-phase fault current, so protection on outgoing feeders operates more reliably. For housing and retail with a high share of single-phase consumers it is typically the preferred option. Yyn0 remains the traditional choice where the neutral is lightly loaded, for example with a mainly three-phase motor load. Note that for the S13-M-400 the load loss depends on the connection: 4520 W for Dy and 4300 W for Yy.

Choose the loss level by load profile. No-load loss is incurred all 8760 hours a year regardless of load, so at low average loading (housing with night-time and off-season lulls, warehouses, seasonal sites) the amorphous SH15-M-400 is the better fit: 200 W no-load loss instead of 410 W, 51% less, with the same 4520 W load loss as the Dyn11 S13-M-400 (SH15 is Dyn11 as standard; with a three-phase three-limb core, Yyn0 can be supplied on request, so state it in your inquiry if needed). The S22-M-NX1 has lower losses than S13, meets energy-efficiency grade 1 to GB 20052-2020 and holds a type-test certificate at 400 kVA, so it suits tenders requiring either. A steady, high load suits the S13-M-400, or the S22-M-NX1 where lower total losses matter more.

Compact substation with a 400 kVA transformer

The 400 kVA transformer is also supplied as part of a compact substation: ZGS American-type pad-mounted substation (KTPN), up to 1600 kVA, or YB European-type substation (BKTP / GKTP), up to 2500 kVA. The substation is assembled and tested at the factory, so the site work mainly comes down to setting it in place and connecting the cables.

Other TMG (S13) ratings