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Roots fan renovation program

2015-03-20

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1. The working principle of the Roots blower
The three-lobe Roots blower is a two-impeller synchronous compression machine. Each three-blade rotor is supported by two bearings, and a pair of synchronous gears are used to keep the relative positions of the two rotors constant. It is a positive displacement blower with forced gas transmission characteristics. As a rotary machine, it has relatively stable working characteristics. There is a small gap between the rotor and the rotor, the rotor and the pump body, and between the rotor and the side cover. Therefore, there is no friction in the working chamber, no contact wear parts; economical and durable, no lubrication is required. Long service life and good dynamic balance. There are six suction and exhaust processes in one week of operation, and the volumetric efficiency is high. The utility model has the advantages of simple structure, convenient use and maintenance, no internal lubrication, and the medium to be conveyed does not contain oil. The support of the pump rotor adopts a reliable anti-backlash structure, the rotating parts are carefully balanced, and the high-precision helical gear is adopted. Therefore, the operation is stable, the noise is low, the use is more reliable, and the long-term operation can be performed under the high pressure difference. The dynamic sealing part adopts the imported patented technology and adopts the imported oil seal to control the runout of the shaft seal to be less than 0.01mm.

2. The situation on the ground
According to the observations of the site and the description of the operator:
The model of the field motor is: Y315MI-6, rated current is 168.8A, rated speed is 980r/min, rated voltage is 380V, running current is about 100A; damper opening is between 50%-90% (according to on-site operators Introduction);

then we analyze the maximum working state of the valve:
The fan of your factory is 90KW (the actual opening of the damper is 90%). The power of the fan is calculated as: 90KW The actual power used is 85% of the rated power of the motor. According to the annual work 300 days, 24 hours a day, 0.5 yuan per kilowatt hour to calculate the annual electricity cost theoretical value (1KW × 1 hour = 1 kWh):
90KW × 300 days × 24 hours × 0.5 yuan × 85% ≈ 276,000 yuan
3. The investment payback period
Apply the inverter to fully open the damper, and the fan speed will be 85% of the original speed, ie (at the highest frequency), the frequency is 42.5HZ, then the actual operating efficiency is:
Operating rate %=[1-(1-15%)3]×100%=61.5%
The theoretical calculation of electricity charges should be:
90KW × 300 days × 24 hours × 0.5 yuan × 61.5% = 19,000 yuan / year
Save electricity costs as:
 27.6-19.9=77,000 yuan / year
(The investment cost can be recovered in one year)

4. The transformation method and circuit diagram
We retrofit to follow the principle of small changes and high efficiency; so the previous line we do not move, just between the previous line and the motor, plus our inverter device, in the variable frequency working mode, driven by the voltage output from the inverter Fan; in the power frequency mode, the fan is driven by the previous mains;
From the previous power supply terminal, the voltage of three-phase 380v is led to the QF terminal of our inverter. As the working voltage of our inverter, the output of our inverter (U, V, W) can output the three-phase we need. The variable power supply controls the speed of our fan motor; thus achieving the air volume we need to operate the motor in the best mode.



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Considering that the operator is operating upstairs, we can put the speed control button upstairs and the operator can operate directly upstairs. Make a tachometer upstairs, the operator can see the current speed of the motor, which is convenient for the operator's operation.
In order to ensure our normal work, we have installed a work-frequency conversion system; when the inverter is faulty, we can switch to the power frequency operation;

5. Advantages after the transformation
(1) The motor can be started smoothly, the starting current is effectively reduced, and the starting current is controlled within 2 times of the rated current;
(2) Reduce the hard impact on the motor bearings, fan bearings and machinery, reduce the maintenance cost of the system and the labor intensity of maintenance;
(3) Make the motor run under the optimal condition and reduce the running cost of the enterprise;
(4) The inverter has overcurrent, overload, overvoltage, overheat, undervoltage and grounding protection for the motor.



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