Power Frequency Induction Furnace Electrical System and Capacity Relationship Explained

Power frequency induction furnace (Power Frequency Induction Furnace) is a widely used equipment for metal melting, and its electrical system design directly affects efficiency and power factor. This article integrates relevant experimental data and configuration instructions, including the relationship between capacity and transformer, compensation capacitor installation, and three-phase balancing methods. The following content is based on standard physics experiment notes, presenting key information directly to help understand the operating principles of power frequency induction furnaces.

Main Components and Connections of Power Frequency Induction Furnace

Low Voltage AC Power Isolation Adjustment (Figure 2-2a)

• Install a set of different voltage level taps on the low-voltage side of the power transformer.
• Use the switching of low-voltage AC power to adjust the furnace voltage.
• Suitable for small-capacity furnaces to ensure voltage stability.

High Voltage AC Control Isolation Adjustment (Figure 2-2b)

• Install adjustment capacitors on the high-voltage side of the power transformer.
• Adjust the primary voltage through vacuum load isolation to achieve the purpose of adjusting the furnace voltage.

Three-Phase Power Balance Installation

Three-phase power balance is key to ensuring grid stability. The power frequency induction furnace is a single-phase load, achieving balance through balancing reactors and capacitors.

Balance Conditions

• The power factor of the phase where the furnace is located equals 1.
• Phase sequence connection forward: Furnace connected between A and B phases; balancing capacitor connected between B and C phases; balancing reactor connected between C and A phases.
• The relationship between the capacity QL of the balancing reactor, the capacity Qc of the balancing capacitor, and the furnace power P is as follows: QL = Qc = P / √3

Adjustment Methods

• Balance by adjusting the three-phase currents of the furnace.
• C-phase current changes with the capacity of the balancing container.
• A and B phase currents change with the material and molten iron conditions in the furnace.
• Balance A and B phases by adjusting the compensation capacitors in parallel with the induction coil.
• Simultaneously change the capacity of the balancing container to achieve three-phase power balance.

Compensation Capacitors

Compensation capacitors are used to improve power factor, and the power factor of power frequency induction furnaces is generally in the range of 0.15 to 0.25.

Installation and Adjustment

• Compensation capacitors are connected in parallel with the induction coil.
• Adjust capacity according to power factor changes.
• When A-phase current is greater than B-phase current, increase compensation capacitors.
• When A-phase current is less than B-phase current, reduce compensation capacitors.
• When A-phase current equals B-phase current, the compensation capacity is appropriate.
• Placed in a dry, ventilated, low-dust indoor environment (refer to Figure 2-4).

Power Transformer Configuration

The power transformer is the core power supply equipment for power frequency induction furnaces. Small-capacity furnaces (below 1 ton) can directly draw power from the low-voltage grid, while large-capacity ones require dedicated transformers.

Capacity and Power Relationship (Figure 2-3)

• Low-voltage AC power isolation voltage adjustment and high-voltage AC control.
• Relationship curve: Capacity and current transformer’s power show a linear relationship, with specific data in the table below.

Domestic Power Frequency Induction Furnace Capacity and Power Transformer Parameters (Table 2-1)

• Primary voltage is 10000V, secondary voltage increases with capacity.
• Structure similar to ordinary power transformers, but secondary voltage is adjustable (there are two methods for secondary voltage).

Hydraulic System and Furnace Body Structure

Hydraulic System

• Includes oil tank, oil pump, oil pump motor, hydraulic system pipes and valves, and hydraulic operation console.
• Used for furnace body tilting and operation control.

Furnace Body Parts

• Components: Furnace cover, furnace frame, furnace body, tilting mechanism, and water and electrical systems.
• Appearance of 10-ton power frequency induction furnace (Figure 2-5).
• Structure of the furnace body part of domestic 5-ton power frequency induction furnace (Figure 2-6).

Operation Precautions for Power Frequency Induction Furnace

• Ensure three-phase balance to avoid grid fluctuations.
• Regularly adjust compensation capacitors to maintain high efficiency.
• Large-capacity furnaces require dedicated transformers to avoid overload.

Through the above configuration, power frequency induction furnaces can achieve efficient melting, suitable for materials like cast iron. Relevant experimental data show that power factor compensation can significantly improve performance.