Summary: In this paper, through introducing INVT Goodrive5000 medium voltage vfd applied to sugar mill house mill presser in Pakistan, especially to illustrate many benefits of VFD and AC motor system instead of steam turbine system. Which is an important technical improvement and use VFD and AC motor is good for production automation and decrease user cost of production.
Keyword: Goodrive5000 medium voltage inverter, VFD renovation, mill presser, steam turbine, Energy saving.
Sugar is an important food material in our daily life. The most of sugar is made from sugarcane. The sugarcane mill factory normally use sugarcane mill and sugar extraction technology to produce sugar. In Pakistan sugar industry there are some factories use steam turbines to drive shredders and squeezers. This system is an old technology and has many disadvantages. Such as engine pressure is not stable, steam turbine system is too noise, steam pipe is hard and costly to maintenance and steam turbine has low steam using efficiency.
Along with development of inverter technology, more and more AC motor and VFD instead of old traditional technology which is steam turbine. This new technology can deal with all of steam turbine disadvantages and also can bring other benefits such as stepless speed regulation, energy saving and low speed high torque.
HAMZA SUGAR MILL factory is located in the Rahimayar Khan Punjab province. It is the biggest sugarcane mill factory in the whole of Asian. The capacity of sugarcane mill is about 30,000 tons/day. It has three sugarcane mill lines, one line is HAMZA 01, another line is MADINA and the last line is HAMZA 02.
Right now all of sugarcane mill lines use steam turbines driving the squeezers. Due to there are many disadvantages by using steam turbines, the customer wants transform one of steam turbines for example by VFD renovation.
Below diagram is the original steam turbine drive system:
Figure 1.The original main electrical circuit diagram
The system work as below:
Firstly the team comes from the steam pipe, the steam temperature is about 385℃ and steam pressure is about 2.29Mpa; then the steam go to stream turbine and drive squeezer through gear box.
3.1 AC motor and VFD solution.
Based on customer requirement, INVT make AC motor and medium voltage VFD solution for them. INVT use AC motor and medium voltage VFD instead of original team turbine and remain gear box. Detailed motor parameters are as follow:
Table 1.Vertical Motor Parameters
3.2 VFD and control solution.
According to the demand on site, the variable frequency drive consists of transformer cabinet, power unit cabinet, control cabinet and automatic bypass cabinet. Due to squeezer need continuous running, INVT support medium voltage liquid soft starter for spare.
The variable frequency driver is the GD5000 medium voltage inverter. There are local/remote button, emergency stop button and power frequency/variable frequency indicators on the panel of control cabinet. For the control system, INVT support remote control box for customer, the control box has one HMI, some indicator lights, start/stop/fault reset/frequency up/ frequency down buttons and speed meter.
The main electrical diagram as below:
Figure 2 The main circuit electrical diagram
The system work process as below:
Firstly, when the medium voltage power is ready, close the VCB in the switch-gear cabinet; Secondly, after VFD is charged run VFD to drive motor; Thirdly, based on actual need running VFD; Fourthly, if VFD is fault, the grid power from bypass cabinet and liquid soft starter to drive motor.
3.4 Calculate air conditioner power:
The VFD model is GOODRIVE5000-A1800-6.3-S. The VFD rated power is 1400KW. The efficiency of VFD is 96%.So the power consumption is 1400KW*4%=56KW.
The VFD room side is:8000mm*3500mm (W*D), so the whole VFD room are is 28 M².There is an experience simulation:1 M²are need 180W cooling power. So the whole room need cooling power is 28*180W=5.04KW. So the whole room power consumption is 56KW+5.04KW=61.04KW
Based on simulation calculation value that is 1HP air conditioner can cool 2.2 KW heat. So the air conditioner rated power is: 61.04KW/2.2KW=27.7.
Finally we suggest customer choose air conditioner rated power is 30HP.
4.Application and Advantage
After using VFD Drive and AC motor, here are some advantages as follow,
1. Low speed high torque; Motor running at 1Hz can support 150% torque.
2. Energy saving; Before using VFD, the power consumption is 1000KW(Only calculate the power, doesn’t mention driven by turbine or electric power) ,after using VFD the power consumption is 6.6KV*55A*0.96*1.732=603.5KW; So the energy saving is (1000-603.5)KW/1000KW=39.6%.
3. Very low torque pulse without causing the resonance between the motor and other mechanical devices, and reducing the transmission mechanism wearing.
4.Perfect output wave, less than 4% of distortion.
5.Easily controlled by DCS system and remote control;
6.Reduce the loss of shutdown maintenance and save plenty of maintenance costs.
Compared with original steam turbine system, the VFD system has much more advantages. The VFD system is easily controlled by REMOTE box and the VFD running speed can automatic adjusted from 0Hz to 50 Hz. The upgraded inverter system works well, customers are satisfied.
 GOODRIVE5000 Series High-voltage Variable Frequency Speed Control System Manual. Shenzhen Invt Electric CO., LTD.