Modernization of the control system of EAF
Nowadays many foundries still using old models of furnaces which have already taken out of production. By the time in such furnaces appear some problems with control system that increase the cost of production. But our company found a good solution – equipping furnaces with a modern automatic control system.
Modernization of the control system of EAF optimizes and speeds up the technical process, and thereby increases the amount and quality of products. At the same time hardware upgrades going without extra costs.
Modernization involves the complete replacement of the control system and, if it’s necessary, refurbishment of mechanical equipment.
We produce automated furnace control system based on "Siemens" controller. It’s intended for:
- controlling traverse actuator of furnace electrodes for automatically maintaining of certain current magnitude (power);
- realization of technological protection and furnace blocking;
- high-voltage vacuum circuit breaker control;
- furnace temperature control;
- energy characteristics control;
- hydraulic system control;
- furnace lifting, tilting, roof slew control.
The control system of EAF consists of:
- Automatic melting conditions controller
- Machine control system
- Furnace temperature control system
All our products are known as "Sigma".
Controlled thyristor rectifier
The first controlled thyristor rectifier was produced in 2010 and was named "Sigma-T".
- work as a part of arc melting furnace as a constant current source;
- DC power supply for the thermo galvanizing, electrolytic, electrophoresis.
Maximum output voltage of the rectifier – 250V.
Maximum output current: up to 2000A for air cooling, up to 8000A for liquid cooling.
Design: up to 4000A – the control cabinet 800 * 600 * 1800 mm; for high currents it can be a double-width control cabinet.
"Sigma 2" controller
"Sigma 2" is a further development of the "Sigma-T" controller. This is the central unit of the control system.
The main advantages of the "Sigma 2":
- reduced response time to current rush;
- diagnostics of thyristor control circuits are available;
- RS–485 channel;
- two-line alphanumeric display;
- supports rectifiers work with electronic polarity commutation.
The controller is made in a small plastic case designed for fixing on DIN-rail.
Nowadays there is a huge amount of amplifiers. However, our experience with the products of different companies showed their lack of safety and stability of operating in high interference environments. Therefore we have created a special two-channel amplifier.
Normalizing amplifier UI-2k-2 was designed for galvanic isolation and amplification of current signals (from shunt 75mV) and voltage. Uses in the thyristor rectifier.
There are two models of drivers – single-channel and dual-channel (designed for rectifier with a current output over 5000A). They used for electrical isolation and control pulses amplification. The number of drivers in the system is determined by the number of thyristors.
Dual channel switch
Designed to control the proportional valve of electrode movement. The lack of "dead zones" in the transfer function has a beneficial effect on the smoothness and accuracy of electrode movement. It can also be used for hydraulic and pneumatic valves control. Operating voltage – 24V, output current – 2A.
Transformer control module
Converts the secondary winding voltage of the transformer to the correct level and filters out high-frequency interference. All electronic modules are manufactured on modern element base and have a small size. Covers of modules are designed for mounting on DIN-rail. Controlled thyristor rectifier is protected against the excess of current input and output.
Usually arc furnace control system is based on programmable logic controller (PLC), but such kinds of control systems are rather expensive.
Our company designed a budget model of controller for DC arc furnaces with a diode or thyristor rectifier. The thyristor rectifier must be running "Sigma 2".
Arc furnace may have one or two arched electrodes.
"Sigma-3" controls the electrodes in manual or automatic mode; measures the melting time, power and power consumption. Controller is equipped with a bright OLED-display with large characters.
Further development of "Sigma 2" controller added the following options:
- work with12-pulse rectifiers
- functioning in batch mode (up to 4 controllers "Sigma-4").