Core Architecture and Technical Evolution
Medium-frequency power supply technology has undergone a leap from early analog control and parallel resonance to today’s fully digital control and series resonance (such as the “one-tows-two” dual power supply system). Its core essence lies in the change of the inverter topology, which directly determines the power factor and overall energy consumption performance of the equipment on the grid side.
Regardless of the topology, the basic physical model of the resonant frequency follows f = 1 / (2 π √LC), but the two circuits have fundamental differences in energy interaction methods, power regulation mechanisms, and their impact on the foundry’s power grid.
Hardcore Comparison: Series vs. Параллельный резонанс
To visually present the differences between the two technical architectures, below is a comparison of their core electrical characteristics:
| Характеристика | Параллельный резонанс (Traditional Topology) | Сериал резонанс (Modern Topology) |
| Inverter Type | Current-source inverter (requires a large-capacity smoothing reactor) | Voltage-source inverter (requires a large-capacity DC filter capacitor) |
| Исправление & Управление мощностью | SCR phase-controlled rectification (power regulated by changing the firing angle) | Diode full-wave rectification or half-controlled bridge (power regulated via chopper or on the inverter side) |
| Коэффициент мощности | Varies with power regulation; often below 0.8 на малой мощности | Remains high across the entire power range ($\cos\phi>0.95$) |
| Harmonic Pollution | Высокий (generates significant high-order harmonics during deep phase control) | Минимальный (rectifier side is fully open, low waveform distortion rate) |
| Startup Performance | Sweep-frequency startup; prone to failure during cold or full-furnace starts | Highly adaptable; nearly 100% startup success rate under various furnace conditions |
Energy Efficiency Analysis and Workshop Benefits
In actual smelting and casting production, energy efficiency is the core competitiveness that determines the cost per ton of steel:
- Advantage of Constant Power Выход: Series resonance circuits can maintain a constant, high power output throughout the entire melting cycle (whether in a cold furnace or full of molten iron). This characteristic significantly shortens the melting time per batch and directly reduces heat radiation losses at high temperatures.
- Line Loss and Transformer Utilization: Parallel resonance draws a large reactive current during low-power stages (such as heat preservation or furnace baking), leading to an unnecessary increase in line loss. В отличие, the constant high power factor of the series topology maximizes the utilization rate of the transformer capacity, effectively avoiding the electrical waste of “a big horse pulling a small cart.”
- Comprehensive Power-Saving Benefits: Compared to traditional parallel equipment, series resonance power cabinets with the same furnace capacity can typically reduce the comprehensive power consumption per ton of steel by 10% к 15% due to improved inverter efficiency and reduced reactive power losses.
