Application du variateur de fréquence moyenne tension dans ventilateur de dépoussiérage pour les fourneaux électriques de la 4ème aciérie de Daye Special Steel Co., Ltd.
2010-1-6 15:23:26
Il y a deux fourneaux électriques, 7# et 8# dans la 4^ème aciérie de Daye Special Steel Co., Ltd..

Chaque fourneau électrique est équipé d’un ventilateur de dépoussiérage (puissance moteur de 1600kw). Six niveaux de soufflage d’air sont nécessaires pour l’adaptation aux nécessités de technologie de production d’acier avec fourneau électrique. Afin d’améliorer l’efficacité opératoire du ventilateur, le ventilateur de dépoussiérage nécessite l’utilisation de la régulation de vitesse par variation de fréquence. Le variateur de fréquence moyenne tension VFD pour le ventilateur de dépoussiérage est de série Harvest, fabriqué par Beijing Leader & Harvest Electric Technologies Co., Ltd. Les tests ont été complétés et ils ont été mis en opération le 13 août 2003.

Technical Requirements for Dusting Fans
There are two electric furnaces 7# and 8# in the Forth Steel Making Plant of Daye Special Steel Co., Ltd.. During the normal smelting process of the electric furnace, a smelting period is divided as the following: (1) add iron, 3 minutes, (2) charge, 3 minutes, (3) supply electricity, 21 minutes, (4) supply electricity and oxygen, 30 minutes, (5) waiting for sampling, 5 minutes, (6) discharge, 5 minutes, (7) block up, 3 minutes, total about 70 minutes. During the process, there are less smoke and dust for (1), (2), (5), (6) and (7) time period and the dusting fans may operate with low speed. The time for operating with low speed is 19 minutes and takes 27% of the total smelting period. Take account of the acceleration and deceleration process of the fan own, the time ratio of operation with low speed may be taken as 20%. Considering the equipment overhaul, 300 days are taken as the annual operation time. According to the smelting technology demands, the air-flow of 1,200,000 m3/hour is needed when the smoke and dust are relatively heavy, and the fan of 1,600W operating with full speed to provide the air-flow 850,000m3/hour. Another fan of 560kW will also operate with full speed, providing the air-flow of 350,000m3/hour. The air-flow of 800,000 m3/hour is needed when the smoke and dust are relatively light, the fan of 560W operates with full speed, providing the air-flow of 350,000m3/hour and the fan of 1,600W operates with regulating speed, providing air-flow 450,000m3/hour (the 52.9% of normal air-flow).

A1-A2 is the time for adding liquid iron and charging (low speed)
A3-A4 is the time for supplying electricity and supplying electricity and oxygen to smelt (high speed)
A5-A6 is the time for waiting for sampling, discharging and blocking out (Low speed)
A2 is the speed rising point, at which the electricity supplying and oxygen supplying signal are collected at the production site and begin to increase the speed from the low speed to high speed.
A4 is the speed decreasing point, at which the electricity supplying stopping, and oxygen supplying stopping signal are collected at the production site and begin to decrease the speed from the high speed to low speed.

In order to adapt the production variation, 5 levels of air-flow from the dusting fan are needed at the low-speed section for adapting the smelting technology demands of the electric furnace.

A-B is the first slow speed section of the low speed section (lowest speed), B-P is the fifth low speed section (highest speed), Q-R is the first low speed section of the low speed section (lowest speed).

B-D is the second low speed section, in which B-C is the fan speed rising time;
D-F is the third low speed section, in which D-E is the fan speed rising time
F-H is the forth low speed section, in which F-G is the fan speed rising time
H-J is the fifth low speed section, in which H-I is the fan speed rising time
When the fan speed is rising, the speed may leap over any speed rising point according to requirements.
At point J, the fan begins speed decreasing.
J-L is the fifth low speed section turning to the forth low speed section, in which J-K is the fan speed decreasing time;
L-N is the forth low speed section turning to the third low speed section, in which L-M is the fan speed decreasing time;
N-P is the third low speed section turning to the second low speed section, in which N-O is the fan speed decreasing time;
P-R is the first low speed section, in which P-Q is the fan speed decreasing time;
Q-R is the first low speed section of the low speed section (lowest speed).

HARVEST-A06/220 VFD is applied to the dusting fan of the electric furnace of the Forth Steel Making Plant of Daye Special Steel Co., Ltd. to perform speed regulation. A bypass switching cabinet of industry frequency is added. The VFD is of voltage source type with direct high-high mode. The main specifications are as follows: Capacity of VFD 2,250kVA, normal output current 220A, input frequency 45Hz-55Hz, normal input voltage 6,000V, allowed voltage fluctuation ±10%, input power factor≥0.96 (when greater than 20% load), output frequency ranging 5 speed levels, adjustable in the range of 0hz to 50Hz (i.e. speed adjustment ranging from 0 to 100%), VFD efficiency ≥98% (not including input transformer), output frequency resolution 0.01Hz, stepless speed regulation, overload capability 120% 1 minute, 150% protect instantly, Acceleration time may be set according to technology requirements. Deceleration time may be set according to the technology requirements.

Table for VFD & Interfaces at the Site

Input channel			Output channel
DI:0.0	Remote start command	Control console	DO:0.0	Remote start command	Defined internally
DI:0.1	Remote stop command	Control console	DO:0.1	Remote Emergency stop command	Defined internally
DI:0.2	Remote Emergency stop command	Control console	DO:0.2	Remote stop command	Defined internally
DI:0.3	Remote/close control selection	Defined internally	DO:0.3	System reset	Defined internally
DI:0.4	Alarming relieve	Defined internally	DO:0.4	Control computer reset	Defined internally
DI:0.5	System reset	Defined internally	DO:0.5	Failure alarming	PLC defined
DI:0.6	Emergency stop	Defined internally	DO:0.6	Failure status	PLC defined
DI:0.7	Controller ready	Defined internally	DO:0.7	Indicator for operating with industry frequency	Control console
DI:1.0	Speed reach given value	Defined internally	DO:1.0	High voltage switch on allowable	Electrical define
DI:1.1	Failure switch off	Defined internally	DO:1.1	High voltage emergency switch off	Electrical define
DI:1.2	High voltage ready	Defined internally	DO:1.2	Indicator for normal operation of VFD	Control console
DI:1.3	Alarming for high temperature of transformer	Defined internally	DO:1.3	Alarming for high temperature of transformer	PLC defined
DI:1.4	Overheat switch off of transformer	Defined internally	DO:1.4	Overheat switch off of transformer	PLC defined
DI:1.5	Alarming for cabinet door interlock	Defined internally	DO:1.5	Spare	Definable by user
DI:1.6	Unit fan failure	Defined internally	DO:1.6	Spare	Definable by user
DI:1.7	Alarming for UPS breakdown	Defined internally	DO:1.7	Spare	Definable by user
DI:2.0	High speed	Control console
DI:2.1	Low speed 1	Control console
DI:2.2	Low speed 2	Control console
DI:2.3	Low speed 3	Control console
DI:2.4	Low speed 4	Control console
DI:2.5	Low speed 5	Control console
DI:2.6	Spare	Definable by user
DI:2.7	Spare	Definable by user

The interface of VFD with PLC control system of the Forth Steel Making Plant: The PLC of the Forth Steel Making Plant is Siemens S7-300 and the built-in PLC of the VFD is Siemens S7-200. When communicating, the PLC of the Forth Steel Making Plant is as the master station, the built-in PLC of the VFD as the slave station, to perform the data communication. The information needed to be transmitted from the VFD to the PLC of the Forth Steel Making Plant include: failure alarming (comprehensive), high voltage switch on allowable, high voltage emergency switch off, analog signal: operating frequency, VFD input current (4-20mA, current source, loading capability greater than 500Ω)
The interface of VFD with the site of the Forth Steel Making Plant: The local control box for the VFD and the Forth Steel Making Plant use hard wires for connection. The local control box of the Forth Steel Making Plant should include: buttons: button for starting (with indicator), button for stopping (with indicator); indicator lamps: indicator for normal operation of VFD, indicator for VFD operation with industry frequency; The VFD and the before-furnace control box of the Forth Steel Making Plant uses hard wires for connection. The before-furnace control box of the Forth Steel Making Plant should include: buttons: high speed button (with indicator), low speed 1 (lowest speed) button (with indicator), low speed 2 button (with indicator), low speed 3 button (with indicator), low speed 4 button (with indicator), low speed 5 (highest speed) button (with indicator); The signals provided to the local control box by VFD: status signal, normal operation of VFD, VFD operation with industry frequency; The signals provided to the VFD by the local control box: remote control commands: start and stop; The signals provided to the VFD by the before-furnace control box: working condition speed commands: high speed command, low speed 1 command, low speed 2 command, low speed 3 command, low speed 4 command, low speed 5 command; interlock signals for the VFD and high voltage switching cabinet: high voltage emergency switch off. The output for all the above digital signals adopts passive contacts, and it is defined as effective at the closed contacts, which capacity of all contacts is AC220V/3A.
Selection for remote/close control for VFD: When the selection control is set to the position for remote control, the control authority is handled to the local control box. When the selection control is set to the position for close control, the control authority is handled to the VFD.

Operation & Tests of the Dusting Fans
The operation record of the VFD for various speed points:

Speed point	Motor speed	VFD Frequency	Input current A	Output current A	Operation
1	225rpm	15 Hz	6.69	55.22	Smoke and dust are less in the periods of adding iron, charging, waiting for sampling and blocking and discharging, and the dusting fans may operate at low speed with a time for low speed of 19 min. total, taking 27% of total smelting period and air-flow of 450,000 m3/h of the large fan needed.
2	375rpm	25 Hz	20.50	66.91
3	375rpm	25 Hz	20.50	66.91
4	525rpm	35 Hz	32.42	99.09
5	645rpm	43 Hz	94.40	126.90
6	750rpm	50 Hz	178.10	201.60	Smoke and dust are more in the periods of power supply, power and oxygen supply, and the dusting fans operate at high speed with a time for low speed of 51 min. total, taking 73% of total smelting period and the large fan operating with high speed to provide air-flow of 850,000 m3/h.

Before the VFD applied to the dusting fans, the operating current of the motor is 180A under various working conditions. After the VFD applied to the dusting fans, the electricity saving rate is more than 47.5% averagely at the low speed section.