Issues with vacuum pump motor power and speed!
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How is the motor speed of a vacuum pump determined, and which parameters of the vacuum pump are related to it? Why do Roots pumps require a 2-stage motor? When a 4-stage motor is used, the pumping volume is reduced by half! Thank you!
The speed at level 4 is half that at level 2, so it’s normal for the pumping volume to be halved as well.
Why reduce the air extraction volume by half? What will be the result if we simply switch to a pump of one size smaller?
Because the speed of a 2-pole motor is fixed, the speed of a 4-pole motor is also fixed, being half that of the former. So the volume of the medium drawn in (air or otherwise) is also half of the former.
For pump motors, the flow rate is proportional to the speed of the pump. You can check the second volume.
The speeds at level 2 and level 4 are different, so the pumping volume is also different
The higher the number of poles, the slower the rotational speed, but the torque may increase (any torque above this level is wasted as long as it’s not sufficient to drive the equipment). In positive-displacement rotating devices where the flow rate is determined by the rotational speed, the flow rate is directly related to the speed; therefore, if the rotational speed is halved due to 4 poles, the flow rate will also be halved~