Application
Vacuum for transformers, capacitors and insulating oil
In the manufacture of transformers, capacitors and switchgear, vacuum removes the moisture from the insulation and draws gas and bubbles out of oil and resin: according to Leybold, windings are dried and impregnated under vacuum, transformer oil is dried and degassed, and circuit breakers are evacuated before SF6 filling. Edwards names the casting, drying and impregnation of transformers and cables under vacuum. Below you can see how the application works, what vacuum the manufacturers name and which of their series are intended for it ā 335 models from 5 manufacturers.
Compare 335 modelsHow it works
- 335Models
- 17Series
- 5Manufacturers
- a few ppmResidual moisture after vacuum drying and impregnation of power capacitors (Leybold)
Touch the points: each part of the system explains itself.
In short
Transformers, capacitors and insulating oil: the key facts
- Drying the insulationAccording to Leybold, the vacuum removes moisture from the insulation; for power transformers Leybold names vapour phase drying with DRYVAC, SCREWLINE and oil-sealed rotary vane vacuum pumps. Edwards names the drying of transformers and cables under vacuum with Stokes.
- Impregnating and castingFor instrument transformers, distribution transformers and insulating bushings Leybold names drying, degassing and the removal of bubbles during impregnation and casting; for power capacitors, according to Leybold, vacuum drying and impregnation reduce the moisture to a few ppm. Edwards names casting, drying and impregnation under vacuum.
- Insulating oilAccording to Leybold, transformer oil is dried and degassed under vacuum; according to Busch, oil is dewatered and degassed in a vacuum chamber. Pfeiffer Vacuum lists transformer oil purification with DuoVane and HiLobe, Edwards oil drying and degassing with EH.
- SF6 fillingAccording to Leybold, air and traces of water are removed before circuit breakers are filled with SF6; Leybold names SOGEVAC B, TRIVAC B, Roots pumps and VARODRY for this.
Operating principle
How it works: Transformers, capacitors and insulating oil
The drawing shows the basic principle in section. The systems and pumps of the individual manufacturers differ in detail.
- EvacuationThe tank or chamber is evacuated with the pumping station; for circuit breakers, according to Leybold, this removes air and traces of water before SF6 filling.
- DryingUnder vacuum the moisture evaporates from the insulation at low temperature; for power transformers Leybold names vapour phase drying.
- FillingOil or resin is filled in under vacuum: according to Leybold, gas and bubbles are removed in the process; according to Edwards, transformers and cables are cast and impregnated under vacuum.
Vacuum and sizing
Transformers, capacitors and insulating oil: how much vacuum is needed
What the manufacturers say about pressure, pumping speed and sizing.
What vacuum
Leybold names a result: vacuum drying and impregnation reduce the moisture of power capacitors to a few ppm.
What pumping speed
The pumping speed depends on the tank volume and the amount of moisture; these pumping stations are named: Leybold DRYVAC with RUVAC WH/WSU and oil-sealed rotary vane vacuum pumps with a Roots stage, Pfeiffer Vacuum HiLobe and DuoVane, Edwards EH for oil drying and degassing, Atlas Copco GLS.
What determines the sizing
The water vapour from the insulation and the vapours of the process: Leybold names vapour phase drying of power transformers, the drying and degassing of transformer oil and the removal of bubbles during impregnation and casting. According to Leybold, air and traces of water must be removed before SF6 filling.
Pump types
Leybold names oil-sealed rotary vane vacuum pumps (SOGEVAC, TRIVAC) with Roots pumps as well as DRYVAC, SCREWLINE and VARODRY. Busch names R5, MINK, COBRA, PANDA/PUMA, DOLPHIN and HUCKEPACK, Pfeiffer Vacuum HiLobe and DuoVane, Edwards Stokes and EH, Atlas Copco GLS.
Technology
Transformers, capacitors and insulating oil: the vacuum pumps the manufacturers name
Listed are the series the manufacturer itself names for this application. āShow only ā¦ā sets the filter of the product overview.
Oil-lubricated rotary vane vacuum pumps
117 models Ā· 1.25ā1,800 mĀ³/h
Liquid ring vacuum pumps
70 models Ā· 25ā16,160 mĀ³/h
Roots vacuum pumps
67 models Ā· 210ā13,540 mĀ³/h
Screw vacuum pumps
47 models Ā· 70ā4,652 mĀ³/h
Claw vacuum pumps
32 models Ā· 18ā1,150 mĀ³/h
Rotary piston vacuum pumps
2 models Ā· 234ā442 mĀ³/h
Product overview
Transformers, capacitors and insulating oil: all 335 models compared
Use the filters on the left to narrow the selection ā by manufacturer, technology and the modelsā key figures, for 50 or 60 Hz.
Atlas Copco GLS series 2 models
Busch COBRA Industry series 36 models
COBRA NS 0070 CPumping speed 70 mĀ³/h 50 Hz85 mĀ³/h 60 HzUltimate pressure 0.03 mbarRated motor power 4 kW 50 Hz4.4 kW 60 HzVariants 
COBRA NC 0100 BPumping speed 110 mĀ³/h 50 Hz130 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 3.5 kW 50 Hz4.8 kW 60 HzVariants 4
COBRA NC 0100 B ECOTORQUEPumping speed 130 mĀ³/h 50 Hz130 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 4.8 kW 50 Hz4.8 kW 60 HzVariants 
COBRA NS 0160 CPumping speed 135 mĀ³/h 50 Hz170 mĀ³/h 60 HzUltimate pressure 0.03 mbarRated motor power 5.5 kW 50 Hz6.6 kW 60 HzVariants 
COBRA NC 0200 BPumping speed 220 mĀ³/h 50 Hz265 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 6 kW 50 Hz7.6 kW 60 HzVariants 4
COBRA NC 0200 B ECOTORQUEPumping speed 265 mĀ³/h 50 Hz265 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 7.6 kW 50 Hz7.6 kW 60 HzVariants 
COBRA NC 0300 BPumping speed 320 mĀ³/h 50 Hz385 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 7.5 kW 50 Hz9.5 kW 60 HzVariants 4
COBRA NC 0400 BPumping speed 350 mĀ³/h 50 Hz420 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 7.5 kW 50 Hz9.5 kW 60 HzVariants 
COBRA NX 0450 APumping speed 350 mĀ³/h 50 Hz420 mĀ³/h 60 HzUltimate pressure 0.1 mbarRated motor power 7.5 kW 50 Hz9.5 kW 60 HzVariants 
COBRA NC 0300 B ECOTORQUEPumping speed 385 mĀ³/h 50 Hz385 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 9.5 kW 50 Hz9.5 kW 60 HzVariants 
COBRA NC 0400 B ECOTORQUEPumping speed 420 mĀ³/h 50 Hz420 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 9.5 kW 50 Hz9.5 kW 60 HzVariants 
COBRA NX 0450 A ECOTORQUEPumping speed 420 mĀ³/h 50 Hz420 mĀ³/h 60 HzUltimate pressure 0.1 mbarRated motor power 11 kW 50 Hz11 kW 60 HzVariants 
COBRA NC 0500 BPumping speed 490 mĀ³/h 50 Hz490 mĀ³/h 60 HzUltimate pressure 0.01 mbarRated motor power 9 kW 50 Hz9 kW 60 HzVariants 
COBRA NC 0630 C VRPumping speed 580 mĀ³/h 50 Hz680 mĀ³/h 60 HzUltimate pressure 25 mbarRated motor power 22 kW 50 Hz22 kW 60 HzVariants 
COBRA NS 0600 CPumping speed 600 mĀ³/h 50 Hz600 mĀ³/h 60 HzUltimate pressure 0.01 mbarRated motor power 15 kW 50 Hz15 kW 60 HzVariants 
COBRA NC 0630 CPumping speed 630 mĀ³/h 50 Hz630 mĀ³/h 60 HzUltimate pressure 0.01 mbarRated motor power 15 kW 50 Hz17 kW 60 HzVariants 
COBRA NC 0630 C ECOTORQUEPumping speed 630 mĀ³/h 50 Hz630 mĀ³/h 60 HzUltimate pressure 0.01 mbarRated motor power 17 kW 50 Hz17 kW 60 HzVariants 
COBRA DX 0650 A PLUSPumping speed 650 mĀ³/h 50 Hz650 mĀ³/h 60 HzUltimate pressure 0.1 mbarRated motor power 15 kW 50 Hz15 kW 60 HzVariants 
COBRA NX 0650 APumping speed 650 mĀ³/h 50 Hz650 mĀ³/h 60 HzUltimate pressure 0.1 mbarRated motor power 12.5 kW 50 Hz15 kW 60 HzVariants 
COBRA NX 0650 A ECOTORQUEPumping speed 650 mĀ³/h 50 Hz650 mĀ³/h 60 HzUltimate pressure 0.1 mbarRated motor power 15 kW 50 Hz15 kW 60 HzVariants 
COBRA NF 0750 APumping speed 750 mĀ³/h 50 Hz750 mĀ³/h 60 HzUltimate pressure 0.05 mbarRated motor power 15 kW 50 Hz15 kW 60 HzVariants Busch DOLPHIN series 70 models
Busch HUCKEPACK series 4 models
Busch MINK series 32 models
Busch PANDA/PUMA series 26 models
Busch R5 series 58 models
Edwards EH series 5 models
Edwards Stokes series 4 models
Leybold DRYVAC series 9 models
Leybold RUVAC WH/WHU series 7 models
Leybold RUVAC WS/WSU series 8 models
Leybold SCREWLINE series 2 models
Leybold SOGEVAC series 23 models
Leybold TRIVAC series 20 models
Pfeiffer Vacuum DuoVane series 12 models
Pfeiffer Vacuum HiLobe series 17 models
No model matches these filters.
Atlas Copco GLS series 2 models
Busch COBRA Industry series 36 models
Busch DOLPHIN series 70 models
Busch HUCKEPACK series 4 models
Busch MINK series 32 models
Busch PANDA/PUMA series 26 models
Busch R5 series 58 models
Edwards EH series 5 models
Edwards Stokes series 4 models
Leybold DRYVAC series 9 models
Leybold RUVAC WH/WHU series 7 models
Leybold RUVAC WS/WSU series 8 models
Leybold SCREWLINE series 2 models
Leybold SOGEVAC series 23 models
Leybold TRIVAC series 20 models
Pfeiffer Vacuum DuoVane series 12 models
Pfeiffer Vacuum HiLobe series 17 models
Models a manufacturer no longer carries in its current range are listed in its āOutdated modelsā section.
Industries
Transformers, capacitors and insulating oil: where the manufacturers name it
The manufacturers list these uses on their own pages.
Electrical industry (transformers, cables, switchgear)
For the electrical industry Leybold names the manufacture of power transformers (vapour phase drying), power capacitors (moisture down to a few ppm), instrument transformers, distribution transformers and insulating bushings, as well as oil degassing and the SF6 filling of circuit breakers.
Industry page: Electrical industry (transformers, cables, switchgear) ā
Energy
For the energy sector Edwards names transformer and cable drying with Stokes: transformers and cables are cast, dried and impregnated under vacuum.
Power generation
Busch and Pfeiffer Vacuum list transformer drying and transformer oil purification for power plants and power generation: Busch with R5, MINK, COBRA, PANDA/PUMA and DOLPHIN, Pfeiffer Vacuum with HiLobe and DuoVane.
Oil and gas
For oil and gas Busch names oil purification with COBRA, R5 and HUCKEPACK (in the text also DOLPHIN): the oil is dewatered and degassed in a vacuum chamber.
Frequently asked questions
Transformers, capacitors and insulating oil: frequently asked questions
How does vacuum drying of transformers work?
The active part stands in the tank or in a drying chamber that a pumping station evacuates. Under vacuum the moisture evaporates from the insulation at low temperature ā according to Leybold, the vacuum removes the moisture from the insulation. The insulating oil is then filled in under vacuum so that no air and no bubbles remain (Leybold: removal of bubbles during impregnation and casting).
Why is a transformer dried under vacuum?
Because moisture in the insulation reduces its insulating effect. Leybold names the drying of the insulation in power transformers, distribution transformers, instrument transformers and insulating bushings, and for power capacitors a residual moisture of a few ppm after vacuum drying and impregnation. Edwards names the drying of transformers and cables under vacuum.
What is vapour phase drying of power transformers?
Leybold names vapour phase drying as a process in the manufacture of power transformers, without describing it in more detail; in it the vacuum removes the moisture from the insulation. Leybold names DRYVAC, SCREWLINE and oil-sealed rotary vane vacuum pumps for it.
Which vacuum pump for transformer drying?
Leybold names DRYVAC, SCREWLINE and oil-sealed rotary vane vacuum pumps, and for capacitors DRYVAC with RUVAC WH/WSU. Busch names R5, MINK, COBRA, PANDA/PUMA and DOLPHIN, Pfeiffer Vacuum HiLobe, Edwards Stokes, Atlas Copco GLS.
How is transformer oil degassed and dried under vacuum?
According to Busch, the oil is dewatered and degassed in a vacuum chamber; according to Leybold, transformer oil is dried and degassed under vacuum. Under vacuum, dissolved gases and water escape from the oil. Leybold names oil-sealed rotary vane vacuum pumps with a Roots stage as well as VARODRY and SCREWLINE for this, Busch COBRA, R5 and HUCKEPACK (also DOLPHIN), Pfeiffer Vacuum DuoVane and HiLobe, Edwards EH.
How much vacuum does transformer drying need?
Leybold names a result: in power capacitors, vacuum drying and impregnation reduce the moisture to a few ppm. The pressure required for this depends on the process and the insulation.
What does the vacuum do when impregnating and potting windings?
According to Leybold, instrument transformers, distribution transformers and insulating bushings are dried and degassed under vacuum, and bubbles are removed during impregnation and casting: resin or oil fills the insulation without trapped air. Edwards names the casting and impregnation of transformers and cables under vacuum with Stokes.
Why are circuit breakers evacuated before SF6 filling?
According to Leybold, air and traces of water are removed before circuit breakers are filled with SF6. Leybold names SOGEVAC B, TRIVAC B, Roots pumps and VARODRY for this.
Which vacuum pump for the manufacture of power capacitors?
For the manufacture of power capacitors Leybold names DRYVAC with RUVAC WH/WSU: vacuum drying and impregnation reduce the moisture to a few ppm.
Oil-lubricated or dry for transformer drying?
Leybold names both approaches: oil-sealed rotary vane vacuum pumps such as SOGEVAC and TRIVAC, with a Roots stage for oil degassing, as well as DRYVAC, SCREWLINE and VARODRY. The choice depends on the process and on the vapours it produces.
A single pump or a central vacuum system?
A central system in a room of its own keeps noise and heat away from production and matches its output to the demand. Central vacuum systems are planned and built by Eugen Theis Vakuum, a company of the Ehrler & Beck group ā more under Central Vacuum.
Does Ehrler & Beck also supply spare parts and service?
Yes. Ehrler & Beck offers original spare parts and accessories as well as maintenance and repair.
Which pump suits your process?
Tell us the application, the medium and the volume ā we advise you on selection, spare parts and service.
