－21－
5.3 Power
requirement
The power required to operate the pump is the total of the power required to overcome
the rotational resistance of the pump (mechanical work) and the power required to
compress the air (compression work)and reaches a maximum at an inlet evacuation
pressure of around 2.7×10
4
to 4×10
4
Pa.
If the inlet evacuation pressure has reduced to 13.3 Pa or less, the compression work
is considerably reduced and more power is consumed in mechanical work.
Figure7. Shows minimum power required operating the pump.
Figure7. Characteristics of motor power
