TMG-630 630 kVA 10/0.4 kV transformer (S13-M-630)

TMG-630 (S13-M-630) 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 44 % compared with the S13. For one 630 kVA transformer this saves about 2190 kWh per year, because no-load loss is present the whole time the transformer is energised, regardless of the load.

Where a 630 kVA transformer is used

A 630 kVA unit is typically chosen for sites with a medium-sized, concentrated load: shopping and office centres, hospitals, production workshops and blocks of multi-storey housing. It is usually installed in indoor transformer substations or in packaged and kiosk-type 10/0.4 kV substations. Where critical consumers need a backup supply, as in hospitals and large shopping centres, two-transformer substations with 2×630 kVA units are the usual arrangement.

• Shopping and office centres
• Hospitals and medical complexes
• Production workshops
• Multi-storey residential blocks
• Two-transformer substations, 2×630 kVA
• Pad-mounted and packaged 10/0.4 kV substations

How to choose a TMG-630

At 70–80% loading the TMG-630 carries 397–454 kW of active load at cos φ 0.9, leaving headroom for motor starting currents and load growth. If the design load fits comfortably within a 400 kVA unit, there is little point paying for 630 kVA; if it exceeds 454 kW or the site is expected to expand, consider 1000 kVA or the intermediate 800 kVA rating. Note also that 630 kVA is the first rating in the series with a short-circuit impedance (uk) of 4.5% (400 kVA has 4%): the LV short-circuit current is slightly lower relative to the rated current, while the voltage drop under load is slightly higher.

For the TMG-630 the load loss is 6200 W for both Dy and Yy, so the vector group has no effect on load losses and can be chosen on network grounds alone. Dyn11 copes better with unbalanced single-phase loads and third harmonics, which circulate in the delta winding, and gives a larger single-phase fault current, helping protection operate reliably. In shopping centres, hospitals and residential buildings with many single-phase consumers, lighting and UPS units, this is usually the deciding factor. Yyn0 remains the traditional choice where the load is close to balanced and the neutral is lightly loaded, for example in workshops dominated by three-phase motors.

The choice between S13, the amorphous SH15 and the energy-efficient S-M-NX1 depends on the load profile. No-load loss runs 8760 hours a year: 570 W for the S13-M-630 against 320 W for the SH15-M-630, while load loss is the same for both. Sites with low average loading, such as residential districts, shopping centres with a deep night-time dip or the standby unit of a two-transformer substation, therefore favour SH15, which comes with the Dyn11 vector group as standard; with a three-phase three-limb core, the Yyn0 vector group can also be supplied on request, so state it in the inquiry if you need it. In workshops with steady high loading the difference matters less and S13 remains a sound choice; where a project requires efficiency grade 1 to GB 20052-2020, consider S-M-NX1.

Compact substation with a 630 kVA transformer

The 630 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