furnace transformers and reactors design and features - Tamini

D. Series Reactor with On-load Tap-changer on Booster Transformer
H.V.
6. A 150 MVA EAF transformer with built-in reactor OLTC’s for voltage and reactance control. (Schematic diagram as fig. D)
L.V.
Main Transformer
Booster Transformer
Reactor
changer, bearing in mind also the cost factor. With a
proper sizing, also the maintenance requirements for
the on-load tap-changer are reduced.
As with the autotransformer, also in the booster
transformer diagram the current transformers
installed in the tertiary winding can give a signal
proportional to the electrode current, independently
from the tap-changer position.
Moreover, this solution permits multiple feeding
voltages, for instance 10 kV or 20 kV, through a
simple change of connection on the primary side.
SERIES REACTOR
WITH ON-LOAD TAP-CHANGER
DIAGRAM D
The possibility of regulating on-load both the
secondary voltage and the system total impedance,
is considered as very interesting and useful by the
furnace operators.
The possibility of optimizing, at every moment of the
process, both the parameters, has brought, in many
steel-works, considerable advantages in tap-to-tap
time as well as in the energy consumption.
A new solution, shown in the diagram, specially
interesting for high power furnaces, has been
developed by Tamini for a 80 MVA transformer
installed in a US steelplant in 1993 and since then
applied in several plants. In this case the series
reactor, with on-load tap-changer, is installed on the
tertiary winding of the booster transformer.
The picture 15 shows the 80 MVA transformer unit.
In that specific case the secondary voltage range on
the transformer is divided in 26 steps; the
corresponding series reactor has a reactance divided
in 12 steps.
In another US steelplant, Tamini has adopted the
same solution, for a 190 MVA transformer with
series reactor with on-load tap-changer, for a
furnace which is considered to be one of the most
powerful in the world (see picture 2).
SATURABLE REACTOR
DIAGRAM E
Developed many years ago, this solution has been
recently revived and applied to large arc furnaces,
to be connected to weak electric network.
Tamini has contributed to this application, developing
an innovative and reliable saturable reactor which
can definitely contribute to reduce the disturbance
(flicker effect) of the furnace on the electric HV
network. The diagram shows a saturable reactor.
Its calculation and project require a proper innovative
design capability, specially in the core design and
E. Saturable Reactor, 1-Phase Diagram
A.C. Power Supply A.C. Windings
D.C. Windings
D.C. Control
AC TECHNOLOGY
Smoothing Reactor
A.C. Power Outlet to Eaf
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