Summary: In this case，through introducing INVT GD5000 medium voltage drive applied to main fan in steel in the Thailand to illustrate economy and characteristics of variable frequency drive. Especially significant energy saving.
Keyword: GD5000 medium voltage drive, TATA steel, main fan, energy saving.
1.Project introduction and analysis
N.T.S steel group PLC. Co Ltd is one steel manufacturer plant in Thailand. This plant belongs to TATA steel group Thailand. TATA steel group is the 6th largest steel company in the world.
There are three main fans used baffle to control air speed and air flow. This is the old technology speed control method, through this way has below disadvantages:
1) Narrow adjusted speed range.
Due to baffle control method can't be elaboration and sensitive, so the system adjusted speed range is narrow.
2) High maintenance costs for pipe network of air.
There is lots of big and long pipe network of air in the working process. Because of air is high pressure, those pipes need much maintenance work and costs during whole plant maintenance period.
3) High power loss.
Because of baffle control method is old and outmoded speed control technology, there is much power consumption during speed adjust period.
Figure 1.N.T.S. steel group PCL
2. System Configuration
2.1 Motor introduction.
Detailed motor parameters are list as follow：
Table 1.Main fan motor Parameters
| Motor Model | Power | Rated Voltage | Rated Current | Rated Speed | Power Factor | Load Type |
| AMA 450L6ABAM | 1000KW | 6600V | 104A | 991RPM | 0.88 | Main fan |
Figure 2.The main fan motor nameplate
2.2 System solution.
Based on INVT experience on steel industry VFD renovation project, INVT can supply whole solution for the customer.
According to customer demand, the variable frequency drive consists of transformer cabinet, power cell cabinet and control cabinet. The GD5000 VFD has function of local/remote button and emergency stop button on control cabinet.
INVT suggest VFD solution:
Table 2.VFDs for main fan
| VFD Model | Power | Rated Voltage | Rated Current | Quantity |
| GD5000-A1250-6.6-S | 1000kw | 6.6KV | 109A | 3 |
Main systme diagram:
Figure 3.The system diagram
Figure 4.The main fans VFD and motor
3. Application and Advantage
After using VFD, there are some major advantages as follow:
1.Wide range speed adjusted.
Because VFD is a step-less speed regulation, the main fans can be run smoothly with wide speed range. It means that the speed adjusted can be elaboration and sensitive.
2.Increase grid line power factor.
The grid line power factor is over 0.97. It can increase efficiency of the grid power.
3.Energy saving.
The main fan and it system running at optimal situation and can save energy. From the site real running situation, the energy saving ratio is about 30% by roughly calculate.
4.Perfect output waveform.
Output waveform is perfect, less than 2% of distortion.
5.Prolong motor working life time.
VFD can keep motor running at optimal situation.
4. Conclusion
Compared with old technology, the VFD driven method has many advantages. Especially significant energy saving. The energy saving ratio can reach 30%. The transformational VFD system works very well, customers are satisfied with INVT solution and INVT VFD met with customer's requirements.
References
[1] GD5000 Series Medium-voltage Variable Frequency Speed Control System Manual. Shenzhen INVT Electric CO., LTD.
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