Air compressors of sliding vane eccentric rotor type
An air compressor includes a stator, which includes an inlet and an outlet and defines a substantially cylindrical bore, and a rotor eccentrically rotatably mounted in the bore. The rotor is connected to be rotated by a three-phase asynchronous electric motor of pole amplitude modulated type which i...
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Zusammenfassung: | An air compressor includes a stator, which includes an inlet and an outlet and defines a substantially cylindrical bore, and a rotor eccentrically rotatably mounted in the bore. The rotor is connected to be rotated by a three-phase asynchronous electric motor of pole amplitude modulated type which is switchable between low speed six pole operation and high speed four pole operation under the control of a controller. A pressure sensor communicates with the compressor outlet and is connected to the controller which is arranged to produce a first signal when the compressor discharge pressure falls below a first threshold value and a second signal when this pressure rises above a second threshold value. Each of the three electrical power supply lines of the motor is associated with a respective impedance, which is connected in parallel with a shunt path including a respective switching device, which is switchable under the control of the controller, whereby when the switching device is closed the impedance is shunted and is effectively switched out of the associated power line and when the switching device is open the shunt path is interrupted and the impedance is effectively switched into the power supply line. The controller is arranged so that when the compressor is operating at low speed and the first signal is produced the motor is switched to operate at high speed and when the compressor is operating and high speed and the second signal is produced the compressor is switched to operate at low speed. |
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