SIEMENS Startup Frequency Converter (SFC System)



Gas turbine power plant as one of the main energy sources is in the attention of consumers for years. In these power plants, the turbine is starting to operate with the help of energy of hot gas pressure caused by fuel combustion (diesel or gas) with air in a closed environment. After turbine start to rotate, generator start to move therefore electrical energy is produced .The air that needed for combustion is provided by the compressor which is coupled by turbine’s shaft and generator and also has been moving with the help of turbine. At the early moments, compressor’s round is not enough to be able to provide the air needed for combustion. Therefore, some equipments named trigger systems (SFC) is used for the initial trigging of gas turbine units. First, turbine with the aid of pressure produced by oil pumps reaches to the speed of 100 rpm then with the aid of trigger system will increase to 600 rpm. In the combustible round (600 rpm) by opening fuel valves and combining with the air produced by the compressor, combustion started and the outcome energy caused an increment in the round of turbine. After reaching turbine to the reliance round (2100 rpm), trigger systems expel out of the process and an independent turbine continues to its rotation.


Startup Frequency Converter (SFC) SIEMENS Technology

Technical Specification:
Type SFC
Device version Stack design
Rated power 3.7 MVA
Rated input voltage 1.4 kV
DC-link power 2.9 MW
DC-link current 1,850 A
DC-link voltage 1,560 V
Thyristor type LSC Thyr. connected in series Thyristor type GSC Thyr. connected in series T1551 N52 1 T1551 N52 1
Voltage rating factor 2.12
Rated losses 36 kW
Required cooling air 7,200 m³/h
Sound pressure level*) 50 Hz power supply 60 Hz power supply 83 dB(A) 85 dB(A)
Weight*) 2,400 kg
DC-link reactor Rated current Starting current Inductance Insulating voltage 1,120 A 1,850 A 2.0 mH 2.5 kV


1-     Primary components such as power sections, DC-link smoothing reactor and sub racks for open-loop and closed-loop control are installed in separate cabinets.

2-     Line stressing during starting remains low. The starting frequency converter does not influence the short-circuit rating of the station service (auxiliaries, etc.).

3-     The optional changeover device can be used to make it possible to start additional gas turbine sets using the same starting frequency converter. As part of this process, the control signals are transferred between the SFC and SEE open-loop control via a serial bus connection.

4-     Mechanical encoders are not required on the rotor for open-loop and closed-loop control and monitoring of the SFC

5-     The generator-side converter can be optimally gated using voltage clocking of the starting frequency converter. Throughout the run-up phase the firing angle is kept close to the inverter stability limit, thereby permitting the converter output to be fully utilized.

6-     The turbine set is accelerated from the lowest speed range, where the generator is not yet able to provide sufficient commutating voltage, by means of DC-link pulsing of the SFC’s line-side converter.