1.Overview

Steel mills are generally equipped with two DC arc furnaces, which power supply and blow oxygen periodically when the electric furnace is smelting. In order to meet the requirements of energy saving and environmental protection, the primary fan of the two electric furnaces is required to operate at variable speed throughout the smelting cycle, at high speed when power supply is blown, and at low speed when oxygen is not blown. Under normal circumstances, the electric furnace produces one furnace of steel every 90 minutes, and the production cycle of each furnace can be divided into the following steps: ① Add waste steel water for 5 minutes, ② power supply and oxygen for 60 minutes, ③ and other samples, steel, steel outlet for 25 minutes. In ①③ time period, the dust is less, the primary fan can run at low speed, the frequency is controlled at 10- -20Hz, the dust is larger in ② time period, the fan runs at high speed, and the frequency is controlled at 40-45Hz.

2.Implementation plans

(1) The FGI FD5000 high voltage frequency inverter is directly connected with the motor, the frequency conversion drag mode is one drag, with power frequency bypass. When converting from frequency conversion operation mode to power frequency operation mode, manual switching is adopted, and the motor can not be directly started through bypass through high voltage frequency converter.

(2) Fan speed regulation and electric furnace sample steel interlock, set high and low speed two gear operation, to realize manual / automatic speed regulation switching function. The operator will set the "manual / automatic" speed control switch and the "speed type" switch. Usually, the high voltage frequency inverter can automatically run at high and low speed. In case of production needs, it can be changed to manual to realize the purpose of speed control operation.

(3) The FD5000 high-voltage frequency inverter has both remote and local control functions. During this machine control, the high voltage inverter can be started and stopped manually through the touch screen on the high voltage inverter control cabinet, and the motor speed and frequency can be adjusted. Remote control is placed in the furnace front control room, equipped with operating table and upper machine, which is controlled by the distribution electrician. Through the electrician of the upper machine can know the operation of the equipment at any time, and the simple remote operation of the high voltage frequency inverter can be realized through the operation table. The distributor can choose the "manual / automatic" speed regulation operation according to the working conditions.

3.Application advantage

(1) The FD5000 high voltage frequency inverter continuously changes the power supply frequency below the power frequency to realize the soft start of the motor. The start is relatively smooth, reducing the impact of the starting current on the motor, bearing and fan, and prolonging the life of the equipment.

(2) Because the high voltage frequency inverter can control the air intake of the fan according to each stage of the smelting process, reduce the heat loss of the electric furnace, and indirectly save energy.

(3) The motor vibration is reduced due to the decrease of the rotation speed, reducing the operating noise of the fan and improving the operating environment of the equipment.

(4) The high voltage frequency inverter is a high-voltage and high-voltage source unit series multiple-level structure, and the power factor can be up to 0.95, which also reduces the harmonic pollution on the grid side.