1.Solid state H.F. welder fortube mill lineadopts the most advanced fixed-angel phase-locking control technique, inverter working status do not change as load tank circuit change, which keep the work at the best small sensitivity resonance status all the time, welder works stably with high efficiency. 2.Solid state H.F. welder fortube mill line has advanced functions like high/low lock-lost protection, frequency upper limit/lower limit protection, invert over-current, tank circuit over-voltage and etc. Also more accurate and efficient on open-circuit, short-circuit, arcing of inductor malfunction, it guarantees welder stable running. 3.Besides regular protections, each inverter bridge adopts multiple protections, such as DC side over-current, AC side over-current, AC side over-voltage and etc. It realizes protection redundancy, guarantees inverter safe running. 4.Rectifier side control circuit adopts singlechip technology which solves automatic phase-recognize successfully, i.e. no requirements on 3-phase power supply input line; thyristor trigger circuit adopts all digital equal interval triggering, it reduces non-characteristics harmonics furthest and power net pollution. 5.Rectifier control circuit has soft startup, soft stop function which prevents welder over-current and over-voltage caused by rising too much of current and voltage when startup/stop. 6.It adopts matching transformer to realize electric isolation and load matching of solid state H.F. welder with merits of whole set high efficiency, easy matching regulation. 7.The welder fortube mill linehas large power allowance, when in good load matching conditions it allows running under 110% rated power for a long time at least. With the adoption of PLC and touch-screen to compose HMI control system which is high intelligent and easy operation. Main design index for solid state HF welder fortube mill line: Output powerDCpowerWelder modelRatedvoltageRatedcurrentFrequencyrangeElectricityefficiencyDesign status60kW80kW GGP60-0.5-H 450V180A450 500kHz≥85%Continuous working system100kW120kW GGP100-0.45-H 450V270A400 450kHz≥85%Continuous working system150kW180kW GGP150-0.4-H 450V400A350 400kHz≥85%Continuous working system200kW240kW GGP200-0.35-H 450V530A300 350kHz≥85%Continuous working system250kW300kW GGP250-0.35-H 450V670A300 350kHz≥85%Continuous working system300kW360kW GGP300-0.35-H 450V800A300 350kHz≥85%Continuous working system400kW480kW GGP400-0.3-H 450V1070A200 300kHz≥85%Continuous working system500kW600kW GGP500-0.3-H 450V1330A200 300kHz≥85%Continuous working system600kW720kW GGP600-0.3-H 450V1600A200 300kHz≥85%Continuous working system700kW840kW GGP700-0.25-H 450V1870A150 250kHz≥85%Continuous working system800kW960kW GGP800-0.25-H 450V2130A150 250kHz≥85%Continuous working system1000kW1200kW GGP1000-0.25-H 450V2670A150 250kHz≥85%Continuous working system1200kW1440kW GGP1200-0.25-H 450V3200A150 250kHz≥85%Continuous working system Note: The frequency of solid state H.F. welder can reach to 800 KHz by special professional design.