Furnace transformer

Main function and features

An electric furnace transformer is used to supply power to an electric furnace, which lowers the high voltage to the furnace-required lower voltage.
Its type varies with the type of electric furnace, so the transformer has many types. Currently we manufacture following types: arc furnace transformers used for steel-smelting (including load- ratio voltage regulator type, ni-load voltage regulator type, and built-in reactor type); blast furnace transformers used for smelting of iron alloy, calcium carbide (single phase, three-phase, load ratio voltage regulator and no-load voltage regulator). All are energy-saving products with low power loss. The cooling modes are self-cooling mode, forced water cooling mode, etc.
 

Manufacture:
Core: effectively upgrade transformer’s no-load performance by below methods:
1)    The core is made of high-permeable grain-orientated top quality cold-rolled silicon sheet and the material is cut with advanced Germany Geoge GmbH automatic shear line with the cut burs controlled within 0.02mm.
2)    The silicon sheet fabrication adopts “no-upper yoke lapped’ technology and all lapped joints of the silicon sheet are 45 full-miters. The laminated core sheets are integrally pressed and adhered with epoxy resin to make the three –leg two-yoke core a strong and flat integral one with good verticality precision, this effectively improves no-load performance and reduces noises.
3)    Bracing plates are used as support between coil leg and inner coil. The iron yoke is tied with epoxy resin-impregnated glass fiber band, and the lower section of oil tank is tightened with counter-pressure bolts. The upper iron and the upper section of oil tank are fixed at three locations. Hence the body inside the oil tank can withstand the vibration during transportation without any shift.
 Winding:
1)    The high-voltage (HV) coil adopts an interleaved-continuous structure to improve the voltage characteristics under impact voltage and make voltage evenly distributed. All stays and pads are chamfered to keep highly reliable insulation.
2)    In the transformer winding there is a zigzag oil guide structure so as to fully cool all areas inside the winding, lower the temperature rise of the winding and the hot points of the winding and prolong the service life of insulation. The HV and MV regulation system are independently provided with voltage-regulating winding to balance the ampere turn of each winding,  effectively lower the axial electrodynamic force generated at short-circuit of transformer and improve abrupt short-circuit withstanding capacity.
3)    The winding adopts radial “0” margin designed, between the core and the paper sleeve of LV winding, and between the LV, HV, voltage-regulating windings, as well as before insertion of stays and shroud plate they are fully dried and tightly matched to ensure extremely good compactness and concentricity of the entire winding.
Oil tank and accessories
1)  The tank wall adopts wide steel sheet, which will be folded into corrugated structure without splicing, in this way welds are decreased and mechanical strength is enhanced, meanwhile, the corrugated wall has diverging effect, and thus plays a role in decrease of noise. The routing troughs and control cabinets of the secondary circuit are all made of stainless steel, so the entire transformer has a simple and good looking.
2)  All sealing surface use quality sealing material and are precision-machined.
3)  On the edge of the tank there are double sealing grooves, and the outer sealing material is used to shade the atmosphere and ultra-ray to protect the inner sealing being damaged, thus at utmost prolonging service life and enhancing reliability of the seal.

Non-excitation-tap-changing Arc Furnace Transformer Technical Parameters.
 

Rated power (KVA)	With series reactor											With series reactor
	Primary voltage	Secondary voltage (V)	Rated secondary current (A)	Type of taping	Connection symbol	Short circuit impedance (%)	Series reactor		No-load loss (KW)	On-load current (KW)	No-load current (KW)	No-load loss (KW)	On-load current (KW)	No-load current (KW)	Short-circuit impedance
							Rated power (KVAR)	Reactance voltage drop (%)							Big	Small
630 800 1000	6 6.3 10 10.5 11	200 170 116 98	1819 2609 2887	No-load tap changing	Dd0 Dy11	8-9 7-8	120 150 190	19	2.4 2.7 3.1	8.6 11.0 14.0	3.0 2.9 2.9	2.2 2.7 3.1	11.0 13.5 16.5	3.0 2.9 2.8	24-26	10-11
1250 1600 2000		210 180 121 104	3437 4399 5499				200 260 320	16	3.6 4.1 4.6	17.5 22.0 27.0	2.6 2.5 2.4	3.7 4.6 5.6	18.5 24.0 28.0	2.6 2.5 2.4	22-24	9-10
2500 3150		220 190 127 110	6561 8267				280 350	11.2	5.2 6.0	32.0 39.0	2.3 2.2	6.7 8.0	34.5 41.5	2.3 2.2	21-23	8-9
4000 5000		240 210 139 121	9623 12028				340 360	8.5	7.6 9.4	46.0 54.0	2.1 2.0				19-21	7-8
6300 8000		260 240 210 139	23900 17765				430 460	5.7	11.8 15.0	63.0 74.0	1.9 1.8