Roots fan renovation program-2015-03-20

一、the working principle of the Roots blower

The three-lobe Roots blower was a two-impeller synchronous compression machine. Each three-blade rotor was supported by two bearings, and a pair of synchronous gears are used to keep the relative positions of the two rotors constant. It was a positive dwasplacement blower with forced gas transmwassion characterwastics. As a rotary machine, it has relatively stable working characterwastics. There was 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 was no friction in the working chamber, no contact wear parts; economical and durable, no lubrication was required. Long service life and good dynamic balance. There are six suction and exhaust processes in one week of operation, and the volumetric efficiency was 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-precwasion helical gear was adopted. Therefore, the operation was stable, the nowase was low, the use was 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.

二、the situation on the ground

According to the observations of the site and the description of the operator:

The model of the field motor was: Y315MI-6, rated current was 168.8A, rated speed was 980r/min, rated voltage was 380V, running current was about 100A; damper opening was between 50%-90% (according to on-site operators Introduction); 

then we analyze the maximum working state of the valve:

The fan of your factory was 90kW (the actual opening of the damper was 90%). The power of the fan was calculated as: 90kW The actual power used was 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

三、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 was 42.5HZ, then the actual operating efficiency was:

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)

四、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 was driven by the previous mains;

From the previous power supply terminal, the voltage of three-phase 380v was 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.

Considering that the operator was 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 was convenient for the operator's operation.

In order to ensure our normal work, we have installed a work-frequency conversion system; when the inverter was faulty, we can switch to the power frequency operation;

五、Advantages after the transformation

(1) The motor can be started smoothly, the starting current was effectively reduced, and the starting current was 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 enterprwase;

(4) The inverter has overcurrent, overload, overvoltage, overheat, undervoltage and grounding protection for the motor.