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    Medium Frequency Power Supply Cabinet

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    Overview

    Medium frequency induction melting power cabinet serves as the core power conversion unit for induction melting production lines. It converts 50/60Hz grid frequency AC into medium‑frequency AC to feed induction coils for metal melting. Two mainstream power device solutions are IGBT power cabinetandSCR thyristor power cabinet, with two typical circuit topologies: series resonant circuitandparallel resonant circuit.
     
     

    IGBT Medium Frequency Power Cabinet

     

    Core Device

    IGBT (Insulated‑Gate Bipolar Transistor), full‑control voltage‑driven power semiconductor. Self‑turn‑off capability, DSP digital control, voltage‑source inverter. Mostly equipped with series resonant topology, parallel resonant version is available on custom request. Working Frequency: 1kHz‑50kHz, wide frequency range, suitable for special alloy melting.
     

    Advantages

    1. Fast fault response, strong resistance to short‑circuit, earth fault and water‑cooling failure; low module damage rate.
    2. High power factor 0.92‑0.98, low total harmonic distortion, less extra reactive power compensation required.
    3. Direct cold‑start from cold furnace, empty furnace or hot furnace; high start‑up success rate. Support one‑rectifier‑multi‑inverter “one drive multiple furnaces” function with flexible power distribution.
    4. Low loop current reduces heat loss on cables and water‑cooling components, 10‑15% energy saving compared with traditional SCR power supply. Disadvantages: Higher initial investment; strict requirements for cooling water quality and heat dissipation. Application: 50‑3000kW, melting steel, iron, copper, aluminum and special alloys. Ideal for continuous casting, multi‑furnace alternate production and new workshops with strict grid‑harmonic requirements.
     

    SCR Thyristor Medium Frequency Power Cabinet

     

    Core Device

    SCR (Silicon‑Controlled Rectifier / Thyristor), half‑controlled current‑driven semiconductor. Trigger‑on only, relying on circuit commutation to turn off. Traditionally matched with parallel resonant topology, series resonant SCR is custom‑made, current‑source inverter. Working Frequency: 200Hz‑10kHz, limited turn‑off time restricts high‑frequency performance. Advantages
    1. Mature technology, widely available spare parts, competitive purchasing cost.
    2. Simple circuit design, easy‑maintenance, friendly for old‑plant retrofitting projects.
    3. Mass‑proven high‑power solution for single‑furnace independent operation. Disadvantages: Power factor drops under partial‑load condition; higher grid harmonic distortion, extra harmonic filter is usually needed. Difficult cold‑no‑load start. Higher risk of cascade component damage under fault condition. Not suitable for one‑drive‑multiple‑furnace layout. Application: 300‑5000kW, cast iron & cast steel melting, single furnace independent operation, budget‑limited projects and legacy workshop renovation.
     

    Series Resonant Circuit Explanation

     

    Circuit Principle

    Induction coil and compensation capacitor are connected in series to build resonant loop, voltage‑source inverter. Minimum impedance at resonance, high loop voltage with low loop current, low heat loss. Advantages
    1. Power factor above 0.95 across full‑load range, low THD, meets CE grid‑quality standards.
    2. Reliable direct cold start; support one‑drive‑two / one‑drive‑multiple furnaces with adjustable power allocation.
    3. Low loop current reduces thermal loss of cables, water‑cooling cables and capacitors, remarkable energy‑saving performance. Disadvantages: High voltage stress on resonant loop, high requirement for component voltage withstand rating, higher manufacturing cost; strict selection for compensation capacitors. Common Matching: Mostly paired with IGBT inverter modules, custom SCR series resonant power supply is available.

    Parallel Resonant Circuit Explanation

     

    Circuit Principle

    Induction coil and compensation capacitor work in parallel for resonance, current‑source inverter. High circulating current inside resonant loop with relatively low output voltage. Classic topology for traditional SCR medium frequency furnaces.

    Advantages

    1. Lower voltage stress on power devices, lower overall equipment cost; well‑proven circuit for easy maintenance.
    2. Good load tolerance for single‑furnace operation; easy component sourcing. Disadvantages: Poor power factor under light‑load condition; large circulating current causes extra heat loss on cables and capacitors. Generally cannot support multi‑furnace shared power supply. Extra reactive compensation & harmonic filter are often necessary. Common Matching: Adopted for most SCR thyristor medium frequency power supplies; also available for custom IGBT parallel resonant units.
     
     
     

    Selection Guidance

    • SCR + Parallel Resonance: Traditional single‑furnace projects, budget‑oriented, old factory upgrading.
    • IGBT + Series Resonance: Prioritize energy saving, grid‑harmonic compliance, multi‑furnace working mode, frequent start‑stop, export‑oriented industrial projects.

    Core Strengths

    Spare Parts
    Casting Machines
    Core Melting Equipment
    Other Supporting Equipment

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