Power supply for electric arc gas heater

Patent metadata

Field	Value
Publication number	US-10856373-B2
Application number	US-201515516055-A
Country	US
Kind code	B2
Filing date	Sep 25, 2015
Priority date	Oct 1, 2014
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

Abstract

This invention concerns power supplies suitable for electric arc gas heaters such a plasma torches. It more particularly relates to the dimensioning of the inductor in the switched-mode DC to DC converter used for feeding the torch. The invention concerns in particular a DC power supply for driving a non-transferred electric arc gas heater, comprising: an AC to DC rectifier providing a potential U 0 ; a DC to DC switching converter having a switching frequency f S ; a current control loop having a latency Formula (I); and, a ballast inductor having an inductance L; characterized in that inductance L is such that Formula (II) and Formula (III). Such a design ensures the stability of the current control loop, while also ensuring a sufficient amount of current ripple to spread out the erosion zone on the electrodes of the torch.

τ
;

(
I
)

L
>

(

U
0

1500

)

⁢
τ

,

(
II
)

L
<

1

f
s

⁢

(

U
0

200

)

.

(
III
)

First claim

The invention claimed is:

1. A DC power supply for driving a non-transferred electric arc gas heater, comprising:
an electrode;
an AC to DC rectifier configured to provide a voltage potential U 0 ; and
a MW-level DC to DC switching converter coupled between the AC to DC rectifier and the electrode, wherein the MW-level DC to DC switching converter comprises:
a pulse-width modulated chopper configured to operate at a switching frequency f s ; and
a ballast inductor coupled between the pulse-width modulated chopper and the electrode, wherein:
the MW-level DC to DC switching converter is configured to have a current control loop latency τ;
the ballast inductor is configured to provide a minimum inductance greater than

(

U
⁢
0

1
⁢
5
⁢
0
⁢
0

)

⁢
τ

to maintain a loop stability criterion; and
the ballast inductor is further configured to provide a maximum inductance less than

1

f
⁢
s

⁢

(

U
⁢
0

2
⁢
0
⁢
0

)

to produce a peak to peak current ripple to enhance wandering of electric arc roots on the electrode under operation.

2. The DC power supply according to claim 1 , wherein the DC to DC converter is a buck converter.

3. The DC power supply according to claim 1 , wherein U 0 >3000 V.

4. The DC power supply according to claim 1 , wherein power delivered to the non-transferred electric arc gas heater is between 1 and 10 MW.

5. The DC power supply according to claim 1 , wherein the non-transferred electric arc gas heater is a non-transferred segmented plasma torch with hollow electrodes.

6. The DC power supply of claim 1 , wherein:
the MW-level DC to DC switching converter further comprises a regulator; and
the current control loop latency τ includes a first time delay of the regulator and a second time delay of the pulse-width modulated chopper.

7. The DC power supply of claim 1 , wherein the peak to peak ripple current is at least 50 amps over a duty cycle range of the pulse-width modulated chopper.

8. The DC power supply of claim 7 , wherein the duty cycle range is at least 20% to 80%.

9. A method of operating a non-transferred electric arc gas heater having a MW-level DC to DC switching converter coupled with an electrode, the method comprising:
providing a voltage potential U 0 to an input of the MW-level DC to DC switching converter; and
providing a current from an output of the MW-level DC to DC switching converter to the electrode, wherein the MW-level DC to DC switching converter comprises:
a pulse-width modulated chopper configured to operate at a switching frequency f s ; and
a ballast inductor coupled between the pulse-width modulated chopper and the electrode, wherein:
the MW-level DC to DC switching converter is configured to have a current control loop latency τ; and
the ballast inductor is configured to provide a minimum inductance greater than

(

U
⁢
0

1
⁢
5
⁢
0
⁢
0

)

⁢
τ

to maintain a loop stability criterion; and
the ballast inductor is further configured to provide a maximum inductance less than

1

f
⁢
s

⁢

(

U
⁢
0

2
⁢
0
⁢
0

)

to produce a peak to peak current ripple to enhance wandering of electric arc roots on the electrode under operation.

10. The method of claim 9 , wherein:
the MW-level DC to DC switching converter further comprises a regulator; and
the current control loop latency τ includes a first time delay of the regulator and a second time delay of the pulse-width modulated chopper.

11. The method of claim 9 , wherein the peak to peak ripple current is at least 50 amps over a duty cycle range of the pulse-width modulated chopper.

12. The method of claim 11 , wherein the duty cycle range is at least 20% to 80%.

Assignees

• Umicore Nv

Inventors

• Ostermeyer John
• Heulens Jeroen

Classifications

• H05H1/36

  Circuit arrangements (H05H1/38, H05H1/40 take precedence) · CPC title

• H05B7/185 Primary

  Heating gases for arc discharge (gas-filled discharge tubes H01J37/32) · CPC title

• B23K9/073

  Stabilising the arc · CPC title

• H05B7/144

  Power supplies specially adapted for heating by electric discharge; Automatic control of power, e.g. by positioning of electrodes · CPC title