Our generation cannot develop economy and should leave environmental protection to the next generation. Matching Roots blower with frequency converter is an important means for many manufacturers to achieve energy conservation. Some traditional power frequency equipment can also realize more energy-saving operation through later frequency conversion transformation. New Qianshun Roots blower can be equipped with frequency conversion control. For the equipment that needs frequency conversion transformation, the new Qianshun Roots blower summarizes the aspects that need attention in the selection of frequency converter:
① Select frequency converter according to load characteristics. There are many kinds of machines with different performance and process requirements, and their torque characteristics are also different. Therefore, before applying the frequency converter, it is necessary to understand the load property of the motor, that is, the load property, and then select the frequency converter.
There are three types of loads: constant torque load, square torque load and constant power load. Different types of frequency converters shall be selected for different types of loads.
② When selecting frequency converter, the actual motor current value should be taken as the basis for selecting frequency converter, and the rated power of the motor can only be used as a reference. In addition, it should be fully considered that the output of frequency converter contains high-order harmonics, which will cause the deterioration of power factor and efficiency of the motor. When selecting motor and frequency converter, appropriate margin shall be reserved to prevent excessive temperature rise from affecting the service life of motor.
How to select frequency converter for Roots blower?
③ If the inverter is to be operated with long cables, measures shall be taken to restrain the impact of long cables on the ground coupling capacitance to avoid insufficient output of the inverter. Therefore, the inverter shall be selected by amplifying the first gear, or an output reactor shall be installed at the output end of the inverter.
④ When the frequency converter is used to control multiple parallel motors, it must be considered that the total length of cables from the frequency converter to the motor is within the allowable range of the frequency converter. If the specified value is exceeded, amplify one or two gears to select the frequency converter. In addition, in this case, the control mode of the inverter can only be V/F control mode, and the inverter cannot protect the motor from overcurrent and overload. At this time, it is necessary to add a fuse to each motor for protection.
⑤ For some special applications, such as high ambient temperature, high switching frequency, high altitude, etc., At this time, the capacity of the inverter will be reduced, and the inverter needs to amplify the first gear selection.
⑥ When a frequency converter is used to control a high-speed motor, because the reactance of the high-speed motor is small, the high-order harmonics also increase the output current value. Therefore, the frequency converter of high-speed motor should be slightly larger than that of ordinary motor.
⑦ Frequency converter For pole changing motor, the capacity of frequency converter shall be fully selected to make its maximum rated current lower than the rated output current of frequency converter. In addition, the motor shall be stopped before pole number conversion during operation, otherwise the motor will idle and the inverter will be damaged under bad conditions.
⑧ When driving the explosion-proof motor, the frequency converter has no explosion-proof structure and should be set outside the dangerous place.
⑨ When a frequency converter is used to drive a gear reducer motor, the application range is limited by the lubrication method of the gear rotation part. When lubricating oil, there is no limit in the low speed range; In the high speed range higher than the rated speed, the risk of lubricating oil consumption may occur. Therefore, do not exceed the maximum allowable speed.
⑩ When the frequency converter drives the wound rotor asynchronous motor, most of the existing motors are used. Compared with the ordinary squirrel cage motor, the winding impedance of the wound motor is smaller. Therefore, over-current tripping caused by ripple current is easy to occur, so the inverter with a slightly larger capacity than usual should be selected. Generally, winding motors are mostly used in situations where the flywheel torque GD2 is large. Pay more attention when setting acceleration and deceleration time.
When the inverter drives the synchronous motor, the output capacity is 10%~20% lower than the power frequency power supply. The continuous output current of the inverter is greater than the product of the rated current of the synchronous motor and the nominal value of the synchronous pull in current.
12、 For compressor, vibrator and other loads with large torque fluctuation and oil pump with peak load, the power frequency operation shall be understood, and the frequency converter with rated output current greater than its maximum current shall be selected. When the frequency converter drives the submersible pump motor, the rated current of the submersible pump motor is greater than the rated current of the normal motor, so when selecting the frequency converter, its rated current should be greater than the rated current of the submersible pump motor.
13. When the converter controls Roots blower, due to its large starting current, when selecting the converter, be sure to pay attention to whether the capacity of the converter is large enough.
14. When selecting frequency converter, be sure to pay attention to whether its protection level matches the site conditions. Otherwise, the dust and moisture on site will affect the long-term operation of the inverter.
