1. The transformer that supplies power to the two intermediate frequency furnaces must be a dedicated rectifier transformer. This is because the high-power inverter will generate harmonic pollution to the power grid because the rectifier transformer uses Y/△ connection method, valve side Y-12 and △-11. The phase difference of the line voltages is 30 °, so that the Y group rectification and the Δ group rectified voltage ripple of the two intermediate frequency power sources also have a phase difference of 30 °, and the two sets of six-phase pulse waves synthesize a 12-phase pulse wave. The combined current waveforms of the two current waveforms in the transformer network side winding can effectively suppress the generation of the 5th and 7th harmonics.

2. Connection diagram of rectifier transformer and two intermediate frequency power supplies:

3, ZS-1250-10/0.38 rectifier transformer technical parameters:

1. Rated capacity: 1250KVA; rated voltage on the grid side: 10±5% (KV) 3Φ/ 50HZ

2. Valve side I rated capacity: 625 (KVA)

3. Valve side I rated output voltage: 380 (V)

4. Valve side II rated capacity: 625 (KVA)

5. Valve side II rated output voltage: 380 (V)

6. Connection group: D do yn11;

7. Impedance drop: Uk=7%

8. Shield between the mesh side and the valve side to reduce the impact of harmonics on the mesh side.

9. With low loss, high reliability, low noise, low temperature rise and so on.

10. With light gas alarm, heavy gas trip; oil temperature alarm, trip; pressure release and other protection.

3.4, the technical standards adopted by the transformer:

11.GB/T18494.1—2001 «Industrial Converter Transformers»

12. JB/T8636-1997 «Power converter transformer».