Vacuum pumping device with electronic control of the motor

1. A vacuum pumping device for evacuating a chamber (CV), said vacuum pumping device experiencing in use a plurality of different identifiable operating phases, comprising:

an oil mechanical pump (P) comprising:

a housing ( 1 ) with a suction port ( 3 ) and a discharge port ( 5 ), the housing having a cylindrical chamber ( 7 ) and a rotor ( 9 ) disposed eccentric with respect to said chamber ( 7 ) said rotor having radial vanes ( 11 ), loaded by springs ( 13 ), said housing being equipped with an electric motor (M) for rotating said rotor ( 9 );

an oil bath ( 15 ), with said oil mechanical pump being immersed therein; and

an electronic control device (C) for supplying said electric motor (M) with power by a voltage signal S U , said electronic control device (C) comprising:

a frequency converter, which controls an excitation frequency F ecc of the voltage signal S U powering said motor as a function of the value of at least a measured current drain I meas of said (M), the variation range of said excitation frequency Fecc being in any case limited in accordance with the upper limiting value for the maximum power P MAX that can be delivered by said electronic control device (C) a different value of said upper limiting value being set for each of said plurality of different identifiable operating phases, and an oil temperature detector ( 17 ) sending to said electronic control device (C) a signal representative of the temperature of said oil bath in the vacuum pump, said plurality of different operating phases being identified in accordance with said signal representative of the temperature of said oil bath, wherein said upper limiting value takes a value P reg during a steady state operation of the pump, and a value P start1 during a cold start phase of the pump, wherein P reg <P start1 , said upper limiting value takes said value P start1 when the temperature of said oil bath is lower than a predetermined limiting value for the temperature of said oil bath.

2. The pumping device as claimed in claim 1 , wherein said upper limiting value for the maximum power P MAX that can be delivered by said electronic control device (C) takes said value P start1 during the cold start phase of the pump for a predetermined time interval.

3. The pumping device as claimed in claim 2 , wherein said predetermined time interval has duration of about 400 sec.

4. The pumping device as claimed in claim 1 , wherein said frequency controlling means comprise a frequency converter, to increase the excitation frequency F ecc of the voltage signal S U by which the motor is powered as long as the measured current drain I meas of the motor is below a predetermined threshold limiting current I comp .

5. The pumping device as claimed in claim 4 , wherein said upper limiting current I comp is given by:

I comp =K 1 ·V set/ V busDC

where:

K 1 is a constant depending on the system,

V set is the equivalent voltage, and

V busDC is the peak voltage supplied to the motor (M).

6. The pumping device as claimed in claim 5 , wherein

I MAX =P MAX /V busDC and

I comp <I MAX .

7. The pumping device as claimed in claim 6 , wherein V busDC =187 V.

8. A vacuum pumping device for evacuating a chamber (CV), said vacuum pumping device experiencing in use a plurality of different identifiable operating phases, comprising:

an oil mechanical pump (P) comprising:

a housing ( 1 ) with a suction port ( 3 ) and a discharge port ( 5 ), the housing having a cylindrical chamber ( 7 ) and a rotor ( 9 ) disposed eccentric with respect to said chamber ( 7 ) said rotor having radial vanes ( 11 ), loaded by springs ( 13 ), said housing being equipped with an electric motor (M) for rotating said rotor ( 9 );

an oil bath ( 15 ) with the oil mechanical pump being immersed therein; and

an electronic control device (C) for supplying said electric motor (M) with power by a voltage signal S U , said electronic control device (C) comprising:

a frequency controlling an excitation frequency F ecc of the powering said motor voltage signal S U as a function of the value of at least a measured current drain I meas of said motor (M),

the variation range of said excitation frequency Fecc being in any case limited in accordance with an upper limiting value for the maximum power P MAX that can be delivered by said electronic control device (C);

a different value of said upper limiting value being set for each of said plurality of different identifiable operating phases; and

an oil temperature detector ( 17 ) supplies to said electronic control device (C) a signal representative of the temperature of said oil bath in the vacuum pump, said different operating phases are identified in accordance with the signal representative of the temperature of said oil bath;

wherein said upper limiting value takes a value P reg during a steady state operation of the pump, and a succession of values P start1 and P start2 during a cold start phase of the pump, with P reg <P start2 <P start1 , said upper limiting value takes the succession of values P start1 and P start2 when said temperature of said oil bath is lower than a predetermined limiting value for the temperature of the oil bath.

9. The pumping device as claimed in claim 8 , wherein said upper limiting value for the maximum power P MAX that can be delivered by said electronic control device (C) takes said succession of values P start1 and P start2 during the cold start phase of the pump, during a succession of predetermined time intervals.

10. The pumping device as claimed in claim 9 , wherein said succession of predetermined time intervals has duration of about 400 sec during which the upper limiting value P start1 for the maximum power P MAX that can be delivered by said electronic control device (C) is applied and of about 300 sec during which the upper limiting value P start2 for the maximum power P MAX that can be delivered by said electronic control device (C) is applied.

11. The pumping device as claimed in claim 8 , wherein said frequency controlling means comprise a frequency converter, to increase the excitation frequency F ecc of the voltage signal S U by which the motor is powered as long as the measured current drain I meas of the motor is below a predetermined threshold limiting current I comp .

12. The pumping device as claimed in claim 11 , wherein said upper limiting current I comp is given by:

I comp =K 1 ·V set/ V busDC

where:

K 1 is a constant depending on the system,

V set is the equivalent voltage, and

V busDC is the peak voltage supplied to the motor (M).

13. The pumping device as claimed in claim 12 , wherein

I MAX =P MAX /V busDC and

I comp <I MAX .

14. The pumping device as claimed in claim 13 , wherein V busDC =187 V.