Along with the frequency conversion technology matures, you need to use the frequency conversion motor industry more and more.
The field use of variable frequency motor is also more and more widely.
According to the different requirements of the motor, therefore, reasonable choice of variable frequency motor parameters, such as pole, fundamental frequency and fundamental frequency power is very important.
On the cost and meet the motor using the environment, plays a vital role.
Due to less number of motor efficiency, power factor and other performance better than the number of multipolar motor, therefore, choose the number of variable frequency motor is the same as ordinary motor, should choose the number of less motor, give priority to choose 4 pole motor.
Sometimes requires high speed, can choose 2 extremely, but also by the 2 pole motor bearing limit speed and rotor critical speed limit, such as Y2 -
Frequency conversion motor 2 but not more than 50 hz frequency range.
Otherwise need to enlarge shaft diameter, in order to improve the critical speed, but also can't more than 60 hz.
Some need a high torque can choose the number of large motor, such as Marine motor.
Due to the power of the inverter output frequency changes of voltage and frequency is below, and the motor flux must remain unchanged, so the motor power in frequency decrease at the same time also need to synchronize to drop, motor torque, constant torque converter.
Rising above fundamental frequency motor frequency voltage remains constant, so the motor power basically remain unchanged, increase gradually decrease with the rotating speed and torque, constant power speed regulation.
Owing to the motor inverter power supply, so the motor reference frequency can be according to the requirements of motor design inverter to adjust to the extent permitted.
Motor power also can according to the requirements of the equipment use constant torque and constant power usage for choice, which is under the condition of the number of selected motor, can be used according to the actual need to choose the fundamental frequency and fundamental frequency power of motor suitable parameters, which makes design compared to the conventional motor frequency conversion motor has more flexibility.
Fundamental frequency to subordinate constant torque speed, the power/speed torque = 9550 *.
Need torque must be speed decreased, the power can be reduced accordingly;
To maintain the fundamental frequency, voltage constant, motor current is reduced accordingly.
Therefore, under the premise of meeting the motor torque requirement, you can try to choose the fundamental frequency of lower.
Such as the original selected fundamental frequency 50 hz, 132 kw, 1485 r/min, frequency conversion motor, 380 v when the current is 241 a, constant torque when the torque is 9550 x 132/1485 = 849 nm;
If the fundamental frequency switch to 35 hz, 4 pole motor, the speed to 1040 r/min, 849 nm torque constant, power into 849 x 1040/9550 = 92.
Is to maintain the 380 v voltage, electric current reduced to (
×241 = 169。
Change the fundamental frequency and fundamental frequency power, the motor current smaller, so for the user, you can use the small capacity of the inverter.
That is about the number of frequency conversion air compressor mechanical and electrical machine, the selection of specific parameters such as frequency range method and theory, for your reference.