TMG-1250 1250 kVA 10/0.4 kV transformer (S13-M-1250)

TMG-1250 (S13-M-1250) 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 45 % compared with the S13. For one 1250 kVA transformer this saves about 3854 kWh per year, because no-load loss is present the whole time the transformer is energised, regardless of the load.

Where a 1250 kVA transformer is used

A 1250 kVA unit is typically chosen to supply medium-sized industrial facilities: spinning and weaving mills, cotton ginning and processing plants, and workshops with many electric motors. It is often installed in two-transformer substations (2×1250 kVA) to provide redundant supply to essential loads. The TMG-1250 is also used for pumping stations, large retail and logistics complexes and outdoor compact substations.

• Spinning and weaving mills
• Cotton ginning and processing plants
• Two-transformer substations, 2×1250 kVA
• Workshops with large motors and compressors
• Water supply and irrigation pumping stations
• Retail and logistics complexes

How to choose a TMG-1250

Size the transformer on the calculated load, taking the diversity factor into account. At the recommended 70–80% loading the 1250 kVA unit covers 788–900 kW at cos φ 0.9 and leaves headroom for motor starting currents and production growth. If the calculated load stays well below that range, a TMG-1000 is the more economical choice, with lower no-load loss and lower capital cost. If the load exceeds 900 kW or the plant is set to expand, move up to 1600 kVA. In a two-transformer substation, size each unit so that the remaining one can supply the essential loads when the other is disconnected.

Choose the vector group by the nature of the load. Dyn11 copes better with unbalanced single-phase loads and with third harmonics from single-phase non-linear loads such as LED and discharge lighting, computers and switch-mode power supplies. It also gives a larger single-phase fault current, which helps the 0.4 kV protection trip reliably on an earth fault. Yyn0 remains the traditional choice where the neutral is lightly loaded, for example with predominantly three-phase motor loads. For textile and cotton plants with an extensive 0.4 kV network and mixed loads, where single-phase faults at the far end of long feeders must be cleared reliably, Dyn11 is typically the better fit.

The choice between S13, the amorphous SH15 and the energy-efficient S22-M-NX1 (S-M-NX1 series) depends on the load profile. No-load loss is incurred 8760 hours a year regardless of loading, and the SH15-M-1250 cuts it by 45% against the S13-M-1250 with the same load loss. At low average loading, as in a two-transformer substation, single-shift operation or seasonal cotton processing, the SH15 is more economical. It is built with Dyn11 as standard; with a three-phase three-limb core, Yyn0 can also be supplied on request, so state it in your inquiry if you need it. Under steady two- or three-shift loading, load loss dominates and the SH15 gains nothing: the S13 remains a sound choice, while the S22-M-NX1, energy-efficiency grade 1 to GB 20052-2020, cuts losses further. For 1250 kVA it also holds a type-test certificate.

Compact substation with a 1250 kVA transformer

The 1250 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