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Geared Variable Speed Coupling

Reliable speed control with geared variable speed couplings from Voith

The core components of the geared variable speed coupling are a hydrodynamic variable speed coupling combined with a mechanical gear stage. The gear stage is designed for the initial increase or decrease of the input driver speed. The variable speed coupling then varies the speed of the driven machine within the required range.

Variable speed drives using a Voith geared variable speed coupling are compact, efficient and offer unbeatable reliability. The reliability of the couplings is 99.97%. The range of application includes powers up to 30 MW and output speeds up to 20,000 rpm. The standard motor and the geared variable speed coupling form a strong pairing in the thermal power plants and in oil and gas industry applications.

The special feature of geared variable speed couplings from Voith is that they provide three functions in one machine: Speed control, transmission for speed conversion, and integrated oil supply that delivers oil to the entire driveline. Besides the enormously reliability the lifetime exceeds 30 years. The supply of spare parts is guaranteed over the entire lifetime.

It has been around for seven decades - the Voith geared variable speed coupling. More than 500 customers in 83 countries trust this type of speed control. Over 10,000 geared variable speed couplings contribute to saving innumerable kilowatt hours of energy.

Your contact

Voith Turbo GmbH & Co. KG
Variable Speed Drives
Voithstraße 1
74564 Crailsheim, Germany

Tel. +49 7951 32-261
Fax +49 7951 32-650

Service, Spare Parts, Repair
Tel. +49 7951 32-1666
Fax +49 7951 32-903

Service Helpline (24/7)
Tel. +49 7951 32-1616

Technical data

Power 1 – 30 MW
Output speed Up to 20,000 rpm
Reliability ~ 99,97%
Lifetime Over 30 years

Advantages and benefits

  • Productivity: The hydrodynamic variable speed coupling varies the speed of the driven machine precisely, quickly and repeatably within the required control range. The motor only supplies the power that the process needs. With speed control, you save a considerable amount of energy over throttle control.
  • Robustness: The robust design ensures that the geared variable speed coupling is less sensitive to environmental effects. Heat, cold, moisture, dust and dirt present no particular challenges to the unit. It can also be used in potentially explosive atmospheres.
  • Motor Start: The hydrodynamic coupling is empty during motor starting, separating the motor from the driven machine. In this way, a motor start under no-load conditions is possible without any additional measures or equipment. Starting the motor under no-load conditions is particularly important for weak power grid conditions, with driven machines having a large mass moment of inertia or in the case of processes with an initially large load torque. Standby drives for boilder feed pumps can be started quickly and safely using the geared variable speed coupling.
  • Maintenance and Repair: We combine wear-free hydrodynamic power transmission with mechanical components that are designed for a lifetime of at least 30 years. The recommended overhaul interval is 8 years and can be planned well in advance.
  • Design: The geared variable speed coupling consists of simple mechanical components. A hydrodynamic coupling, a gear stage and the oil system are integrated into a single housing.

Typical applications

Thermal power plants
- Boiler feed pumps
- Coal mills

Combined cycle power plants
- Boiler feed pumps

Nuclear power plant
- Feed pumps

Natural gas liquefaction (LNG)
- Flash-gas compressors
- Refrigerating compressors
- Boil-off gas compressors

Gas transport
- Pipeline compressors

Offshore platforms
- Gas lift compressors
- Export gas compressors
- Loading pumps

- Injection compressors
- Export gas compressors
- Water-injection pumps
- Loading pumps

Refineries and petrochemicals
- Process gas compressors
- Hydrogen recycling compressors

Gas treatment
- Wet gas compressors
- Refigerating compressors
- Acid gas compressors

Oil and gas prodction
- Gas lift compressors
- Depletion compressors
- Injection compressors

Technical information

Design and function

  • The hydrodynamic variable speed coupling and the mechanical gear with double helical design are integrated into an enclosed housing with a horizontal split.
  • The gearbox is located before or after the variable speed coupling depending on the customer's application.
  • Using the hydrodynamic power transmission principle, a fluid flow transmits the power from the pump wheel to the turbine wheel.
  • The pump wheel rotates at a constant input speed and the turbine wheel at variable output speed.
  • The scoop tube varies the coupling filling. The filling amount determines the power transmitted and consequently the speed of the driven machine.
  • An actuator varies the position of the scoop tube. In this way, the speed can be controlled in a stepless manner over a wide operating range.
  • Working and lube oil are supplied to the geared variable speed coupling from the integrated oil tank. The working and lube oil circuits are seperate.
  • The integrated lube oil supply system can supply lube oil to the motor and the driven machine. A seperate lube oil supply system is not required.


Scoop tube positioning using the Voith VEHS electrohydraulic actuator

The Voith VEHS electrohydraulic actuator positions the scoop tube fast and in a stepless manner at high precision. The short reaction time and the high position accuracy adapt the operating behavior of the driven machine to the process conditions exactly.