Device and method for driving a vacuum pump

Abstract

A vacuum pump drive having an electric motor and a frequency converterelectrically connected to the electric motor and arranged at a distance to the motor, wherein in the electric feed line from the frequency converter to the electric motor a transformer in the form of a transmitter of ferrite or sinter material is arranged.

Claims

1. A vacuum pump drive having an electric motor and a frequency converter electrically connected to said electric motor and arranged at a distance to said motor, wherein in the electric feed line from said frequency converter to said electric motor a transformer in the form of a transmitter of ferrite or sinter material is arranged.

2. The vacuum pump drive according to claim 1, wherein a first section of the electric feed line between the frequency converter and the transformer is made considerably longer than a second section of said electric feed line between said transformer and the electric motor.

3. The vacuum pump drive according to claim 2, wherein the first section is at least twice as long as a second section of the electric feed line between the transformer and the electric motor.

4. The vacuum pump drive according to claim 2, wherein the frequency converter and the transformer are configured for transmitting a first voltage via the first feed line section, which is larger than the voltage transmitted via the second feed line section between said transformer and the electric motor.

5. The vacuum pump drive according to claim 4, wherein the first voltage is at least twice as large as the voltage transmitted via the second feed line section between the transformer and the electric motor.

6. The vacuum pump drive according to claim 1, wherein the frequency converter is arranged at a distance of at least 100 m from the electric motor.

7. The vacuum pump drive according to claim 6, wherein the transformer is arranged closer to the electric motor than to the frequency converter.

8. The vacuum pump drive according to claim 1, wherein the electric cables of the first feed line section between the frequency converter and the transformer have a small cross-section of approximately 1.5 mm.sup.2.

9. The vacuum pump drive according to claim 1, wherein the cables of the first feed line section between the frequency converter and the transformer have a capacitance of less than approximately 100 pF/m.

10. The vacuum pump drive according to claim 1, wherein the cables of the first feed line section between the frequency converter and the transformer are made thinner and with a smaller capacitance than the cables of the second feed line section between said transformer and the electric motor.

11. A method for driving a vacuum pump having a vacuum pump drive according to claim 1, wherein via the first feed line section between a frequency converter and a transformer a higher voltage and a smaller current are transmitted than via the second feed line section between said transformer and an electric motor.

12. The method according to claim 11, wherein the voltage of the first feed line section is at least five times and preferably at least eight times as large as the voltage of the second feed line section.

13. The vacuum pump drive according to claim 3, wherein the first section is approximately ten times as long as a second section of the electric feed line between the transformer and the electric motor.

14. The vacuum pump drive according to claim 5, wherein the first voltage is at least eight times as large as the voltage transmitted via the second feed line section between the transformer and the electric motor.

15. The vacuum pump drive according to claim 6, wherein the frequency converter is arranged at a distance of at least 500 m from the electric motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereunder exemplary embodiments of the disclosure are explained in detail with reference to the drawings in which:

(2) FIG. 1 shows a first exemplary embodiment,

(3) FIG. 2 shows a second exemplary embodiment, and

(4) FIG. 3 shows a third exemplary embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) In all three illustrated exemplary embodiments an electric motor 12 for driving a vacuum pump 14 is provided. The electric motor 12 is supplied with an electrical voltage of variable frequency and amplitude from a frequency converter 16 via an electric feed line 18. The torque of the electric motor 12 is generated, depending on the amplitude and the frequency, via the frequency converter 16.

(6) The frequency converter 16 is arranged at a distance of at least 800 m and preferably 1 km from the electric drive motor 12 and the vacuum pump 14 due to safety requirements. For reducing the electrical losses during the transmission of the drive voltage in the long electric feed line 18, an electric transformer 20 in the form of a transmitter of ferrite or sinter material is provided in the feed line 18. A first section 18a of the electric feed line 18 is the feed line section between the frequency converter 16 and the transformer 20. A second fine section 18b of the electric feed line 18 is the feed line section between the transformer 20 and the electric motor 12. It is common to all three exemplary embodiments that the first feed line section 18a is considerably longer that the feed line section 18b. While the feed line section 18b has a length of only a few meters, the feed line section 18a is several hundreds of meters long.

(7) The frequency converter 16 and the transformer 20 are configured to transmit a voltage of several hundreds of volts, 400 V for example, via the first feed line section 18a, while a voltage of only a few tens of volts, 48 V for example, is transmitted via the feed line section 18b. When the 48 V alternating voltage of the second feed line section 18b is used, the safety requirements for radioactive environment, high temperatures, explosive environments or large accelerating plants, for example, are complied with, while the line losses during the transmission from the frequency converter to the electric motor 12 are reduced by the first feed line section 18a, which is as long as possible, transmitting a considerably higher alternating voltage at considerably smaller losses.

(8) The cross-section of the lines used for the first feed line 18a is smaller than the cross-section of the lines used for the second feed line 18b and amounts to a maximum of 1.5 mm.sup.2. The capacitance of the lines used for the first feed fine section 18a is also smaller than the capacitance of the lines used for the second feed line section 18b and amounts to less than approximately 100 pF/m.

(9) Thus, while via the first feed line section 18a a high voltage and a small current are transmitted over a long line through a thin cable having a low capacitance and low losses, a high current and a small voltage are transmitted via a short feed line section 18b.

(10) The essential advantage of the disclosure is that, depending on the position of the transformer 20 inside the feed line 18, the current load of a major portion of the motor feed line 18 is considerably reduced. Thus the line losses are substantially minimized. At the same time, the electrically conductive cross-section of the feed line 18 can be considerably reduced. Thus costs are saved and at the same time the electrical capacitance of the feed line and thus the charge-transfer currents or reactive currents in the drive converter 16 are reduced.

(11) In the exemplary embodiment of FIG. 1 a three-phase transformer is operated inside a three-phase feed line 18.

(12) In the exemplary embodiment of FIG. 2 a two-phase transformer is operated in a two-phase feed line 18.

(13) In the exemplary embodiment of FIG. 3 two parallel connected two-phase transformers 20 are operated in a three-phase feed line 18.