Transformers Supplying the Induction Electrical Furnaces

rated 250 kVA ÷ 5000 kVA

Miscellaneous

Self cooled, oil immersed three phase power transformers, operating at 50 Hz frequency, meant to supply the induction furnaces up to 20 tons capacity.

The LV winding is manufactured with 10 voltage control steps, the tap changing being performed by means of a special tap changer, operated both manually and by remotely controlled booster.

Tap changing is performed only with the de-energized transformer.

The transformer in service is installed indoors, next to the induction furnace, the ambient temperature not exceeding +40° C.

Conditions of operation

The transformers comply to the data are shown in table I.

The main dimension are shown in table II.

Construction features

• The magnetic circuit is made of carlyte insulated, grain oriented, cold rolled silicous steel sheet with low specific losses.

• The LV windings are cylindrical type, in one or two flat coils and are made of paper insulated copper wire.

• The HV windings are layered or continuous type and are made of paper insulated copper or aluminium wire. The windings are concentrically placed, the LV one being outsides.

• The tank and cover are made of steel. The coolers, made of elliptical tubes, are welded on the tank.

Notes

Transformers having other ratings and other ratios may be manufactured at request.

The purchase order must contain compulsorily the following: rated output; ratio; number of steps on the LV side and their size in volts; connection group vectors; steps on which the transformers rating remains constant.

Table I

Furnace capacity	t	0.5	1.1	2	3	6.3	12	20
Transformer rating	KVA	250	400	630	1000	1600	2800	5000
Primary voltage	V	6000	6000	6000	6000	6000	6000	6000
		10000	10000	10000	10000	10000	10000	10000
		20000	20000	20000	20000	20000	20000	20000
Secondary voltage	V	550-125	550-125	550-125	550-125	550-125	1000-222	2500-500
Steps number		10	10	10	10	10	10	10
Connection group vectors		Dyn5	Dyn5	Dyn5	Dyn5	Dyn5	Dyn5	Dyn5
No load losses	W	800	900	1750	2500	3000	4500	6500
		850	1100	1950				7200
Copper losses	W	6800	7600	8000	12000	21000	26000	38000
			8500
No load current	%	2.1	1.9	1.8	1.6	1.6	1.4	1.2
Impedance voltage	%	6	6	6	6	7	6	7
Overall weight	Kg	2580	2750	3650	5200	6250	9350	15500
		2600	2900	4200	5300		9450	17000
Oil Weight		930	960	1250	1600	1850	2850	4100
			1000	1410	1700			5000

Table II

Rating	KVA	250	400	630	1000	1600	2800	5000
Primary voltage	V	6000	6000	6000	6000	6000	6000	6000
		10000	10000	10000	10000	10000	10000
		20000	20000	20000	20000	20000	20000
L	mm	1780	1780	2085	2200	2270	2550	2750
			1790	2150
W	mm	1080	1150	1045	1220	1420	1600	3100
			980	1150
H	mm	2460	2460	2600	2870	3150	3460	3850
			2570	2650
E	mm	670	670	820	820	820	1100	1435
f1	mm	300	300	300	300	300	300	300
		320	320
f2	mm	120	120	130	140	140	140	300
f3	mm	120	120	145	180	180	180	300