Excitation - Thyricon

Excitation - Thyricon 

The Thyricon excitation family represents the extensive experience and knowledge of Voith Hydro as one of the major hydropower generator manufacturers. Our excitation product line offers best-in-class technology to feed the hydro generator’s field windings as well as to intelligently and reliably control generator voltage and reactive power.

Thyricon is a highly flexible and adaptable product that can be easily implemented. With an application range up to 4 000 Ampere rated current, at 50 or 60 Hz, it meets all protection and control requirements.

Benefits and features

Thyricon offers many benefits for all types of projects in the hydro world. This applies to new installations, modernization, and rehabilitation projects. Our ambition is to surpass existing standards in the field of hydropower excitation systems through continuous improvement.

Thyricon features several configurations including redundant controllers and fully or n+1 redundant thyristor bridges. The comprehensive controller software includes special features like trend function and special modules to support the service and commissioning team.

  • Reliable technology and engineering
  • Wide range of excitation current
  • Fulfils fast grid response and stability demands
  • Easy integration into existing power stations and control systems


Digital Voltage Regulator

As suggested by its name, the digital voltage regulator‘s primary task is to keep the voltage of the generator terminals at a constant level. Nonetheless, the digital voltage regulator is also expected to maintain the generator inside its capability limits and assist in damping low frequency oscillations in the power system.

Thyricon employs state-of-the-art industrial programmable logic controllers for performing the digital voltage regulation tasks, stator and rotor limiting functions, power system stabilizing and interface with other systems in the power plant. The regulation and control software are engineered according to IEEE standards; which guarantees the best system behavior as well as reliable and safe operation within the generator limits.

Interaction with the digital voltage regulator is provided by a user friendly Human-Machine Interface. This operation panel comprised of an LCD and a keyboard for easy operation. System status and alarms can be monitored both remotely and locally. As an additional function, trend displays on the operator panel are provided. All these features make this HMI an excellent diagnostic tool to accelerate commissioning and maintenance of the Voith Hydro Thyricon Excitation System.


Benefits and features

Controllers are based on standard Siemens electronic components and parts. The program language of the Thyricon controllers is identical to the Siemens automation product line, which facilitates the handling of the excitation system. Therefore, training and maintenance becomes easier and faster. Software programming, as well as commissioning, maintenance and reporting tools are available on personal computers.

Main control and regulation functions

  • Automatic voltage regulator
  • Reactive power and power factor controller
  • Power system stabilizer according to IEEE 421.5 PSS2B
  • Field current and field voltage regulator
  • Field flashing supervision and control
  • Fast generator field de-excitation, by inversion of excitation voltage
  • Smooth transitions due to automatic follow-up between control modes as well as redundant channels

Additional functions

  • User friendly interface for the operation and maintenance crew including parameter changing accessible from the operator panel
  • Communication with the other systems in the power plant
  • Reactive power unloading before disconnecting the machine from the grid
  • Powerful testing and maintenance tools incorporated in the operator panel
  • Monitoring of temperature of power components and air flow of the cooling fans
  • Supervision and protection of main equipment parts
  • Trend functions


Static Excitation System

Superior requirements on dynamic control characteristics and the need to improve the grid stability are clear decision criteria in favor of a static excitation system out of the Voith Hydro Thyricon family.

In Thyricon static excitation systems, the field winding of the generator is fed directly by a fully controlled thyristor rectifier bridge. The direct access to the rotor winding is the reason for the superior dynamic characteristics of such systems. Typically, the power source for the rectifier bridge is derived from the generator stator itself, also known as self-excited. State-of-the-art power electronics combined with a self-excited configuration, enhance the reliability of the static excitation system as its power part is independent from the rest of the power plant. The high ceiling voltage capacity and wide-range operating voltage of the rectifier bridge guarantee that Thyricon continues working even during severe voltage drops in the power system.



  • Superior dynamic control characteristics
  • Negative field forcing capabilities
  • Rotor temperature estimation (field voltage and current)
  • Static power part, no rotating machines required

Common protections and supervision which are available

  • Excitation transformer overcurrent/short circuit
  • Temperature rises in the excitation transformer
  • Rotor earth fault
  • Overload in the field circuit
  • Non-conducting thyristor branch
  • Fan fault


Brushless Excitation System

On smaller generation, instead of static exciter, a directly driven AC exciter machine with the rectifier mounted on the generator shaft is employed. The main advantage of this solution compared with DC exciters is that the problems associated with the commutator and brushes can be completely eliminated. The brushless system eliminates the slip rings and thus all current-carrying brushes. The brushless excitation system is used for high speed synchronous machines with horizontal shaft as well as for hydro power generators.

Common protections and supervision which are available

  • Detection of diode faults in the rotating rectifier of the main exciter
  • Protection against overload in the exciter field winding
  • Earth fault protection. To be connected to an auxiliary slip ring in the main generator field.
  • Thyristor converter failure