INVT GD5000 -S Series MVD Applied to Coal Mill Fan and Raw Mill fan of Cement in India

Abstract: This article introduces the application of INVT GD5000 series medium-voltage four-quadrant vector VFD in the Coal mill fan and raw mill fan , cement, India.

Keywords: GD5000, Coal mill fan and Raw mill fan , Medium-voltage Variable-frequency Drive, cement, India.

1. Forewords

Raw mill fan in cement industry carries gas and raw meal. The pressure drop in raw mill fan is very high. If a vertical roller mill is used for raw grinding in cement industry then a large raw mill fan is installed. Usually cement industries use centrifugal fans to carry out this process.

Coal mill fans: In cement industry coal mill fans are used to supply required air for burning coal and remove the exhaust gases produced after burning. These fans help in effective burning of coal inside the mill. For a large clinker line there are usually 2 or 3 cement mills

The distribution of compressed air in iron-making equipment can be divided into sintering area, raw material area, coke oven area and blast furnace area. The compressed air in the steelmaking plant is mainly used for continuous casting, converter pneumatic and purging, and aerosol cooling for continuous casting. Compressed air in hot rolling mills is mainly used for mill and furnace pneumatic equipment and cold rolling purge. The compressed air of the unit is mainly used for strip cleaning, pickling, continuous winding, pneumatic equipment and hot dip galvanizing equipment. Application of compressor in iron and steel industry.

Generally speaking, the compressed air produced by the air compressor in the compressed air system of iron and steel enterprises is treated by the cold and dry machine, and the pressure dew point is reduced to 3-5C to provide the user with power (ordinary) compressed air; Or the compressed air treated by the adsorption dryer is processed by the cold dryer. Reduce the water content to a pressure dew point below -20 ° C to remove dust particles with a dust content of less than 5 m and less than 5 mg/m. Oil content less than 1 mg/m3, used as compressed air for the instrument for user use. In addition, the compressed air used for steam mist cooling during steelmaking and continuous casting does not require direct air compressor exhaust to the continuous casting.

2.  Project introduction

Before the reconstruction of  cement, the old rotor resistance method was used. However, there are the following disadvantages:

1)  The rotor resistance control method is that the efficiency is low because of the additional losses present in the resistors connected within the rotor circuit. 

2) The efficiency is greatly reduced at low speeds because of the higher value of the slip.

3) His starter can only be used for starting a slip ring induction motor.

4) It needs frequent maintenance due to presence of slip rings and carbon brushes.

3.  Motor parameter

4. Project reform

* VFD Selection:

The project adopts GD5000 series MVD independently developed and produced by INVT. The MVD is a medium voltage variable frequency speed regulating device of vector control H bridge series multi-level technology. The original old system can still be used at present, so it will not be dismantled temporarily, and will be reserved as the backup system.

5. VFD principle

INVT GD5000 series VFD is a high-tech energy-saving product, which adopts advanced IGBT power unit multi-level technology, digital control technology and SPWM pulse width modulation technology. It has the advantages of high power factor, high efficiency, energy saving, high stability etc… and has the rated power energy feedback ability.

Each phase of the VFD is composed of six power units in series, and the three-phase Y is connected to the output. The output adopts the SPWM wave superimposed by 6 power units in 6.6 kv of each phase to form high-quality output waveform, which is supplied to the motor.

Optical fiber communication is adopted between control cabinet, power unit cabinet, transformer cabinet and bypass cabinet to prevent electromagnetic interference. Achieve complete isolation of high and low voltage, improve safety.

The input side of the power unit is composed of fuse, rectifier and filter parts, and the rectifier part is composed of six IGBT. The inverter consists of four IGBT H bridge inverter outputs, and the motor is driven by the unit series.

6. MVD system advantage

* High reliability

The GD5000 series inverters of INVT have perfect protection functions, such as overcurrent, overvoltage, overload, stall and other protection functions.

* Small start-up current

The impact current in the process of starting and accelerating is small, and the maximum starting current in the process of accelerating does not exceed 1.9 times of the rated current.

* Wide range of speed regulation

VFD system belongs to the step-less of peed regulation, the motor control in the process of acceleration and deceleration is stable. The speed regulation is soft.

* Production efficiency is high

The stability of the INVT GD5000 series VFD is high, and the speed does not change with the change of the load. The VFD can control the motor to run stably at a given speed.

7.  Field site photos

Field site photos

8. Complimentary Close

The practice has proved that the in Coal mill fan and Raw mill fans runs well after the technical transformation of VFD, the energy consumption of the fans of coal mill and raw mill is reduced and the power factor of the power grid is also improved. Facts have proved that the Medium Voltage VFD has superior product performance, in the cement industry in the energy saving transformation application can create huge economic benefits.In the energy saving and environmental protection has played an important role. It can completely replace the traditional control mode and has very high promotion value.