Medium-frequency Induction Heating Power Supply: Vacuum Melting and Large Workpiece Heating Equipment

MF Induction Heating Power Supply

Medium-frequency induction heating power supplies (typically with a frequency range of 1–10 kHz) are devices that heat metals using the principle of electromagnetic induction. They are suitable for industrial applications such as heat penetration, melting, forging, and annealing. Compared with high-frequency heating, medium-frequency heating offers greater penetration depth, making it ideal for processing thicker metal workpieces.

1. Working Principles of Medium-Frequency Induction Heating Power Supplies

Electromagnetic Induction: Medium-frequency alternating current (1–10 kHz) passes through an induction coil to generate an alternating magnetic field, inducing eddy currents within the metal workpiece to produce heat.
Skin Effect: Current concentrates on the workpiece surface but penetrates deeper (1–10 mm) than high-frequency heating, making it suitable for larger workpieces.
Heat Penetration Effect: Ideal for scenarios requiring overall heating, such as forging and melting.

2. Main Components and Their Functions

Component	Function Description
Medium-Frequency Power Cabinet	Converts mains frequency electricity (50/60 Hz) to medium frequency (1–10 kHz). Core components include IGBT/SCR inverter modules.
Induction Coil	Made of copper tubing with water cooling. Customized according to workpiece shapes (e.g., cylindrical, flat).
Capacitor Bank	Compensates for reactive power and improves heating efficiency (resonant capacitors).
Cooling System	Water-cooling system (cools power supply, coil, and capacitors) to prevent overheating.
Control System	PLC/touchscreen control for adjusting power, frequency, and heating time, supporting automated production.

Product Overview

This medium frequency induction heating system is designed around the series-resonant inverter structure, consisting of a MF power supply, a compensation capacitor box, and a customized induction coil. It is a high-efficiency, cost-effective solution widely used in metal melting, heat treatment, and thermal fitting applications.

Technical Highlights

Feature	Description
1. Power Structure	Series-resonant inverter topology using IGBT/MOSFET technology
2. Frequency Range	1–20 kHz, ideal for forging, melting, annealing, surface hardening
3. Capacitor Box	Provides capacitive compensation for inductive load, improves power factor
4. Induction Coil	Acts as both inductor and heating element, typically made from 3–10m copper tubing
5. High Efficiency	Operates at resonance point for maximum energy transfer and minimal losses
6. Compact System	Integrated MF power + capacitor + coil makes it easy to deploy and maintain
7. Application Flexibility	Suitable for melting, hot fitting, sintering, forging, spraying & more

Technical Explanation

The system works on LC series resonance, where the induction coil (L) and capacitor box (C) form a resonant circuit. At resonance, impedance is minimized, and current is maximized—allowing efficient energy transfer to the workpiece via eddy current heating.

However, the design also has several limitations:

Induction coil length is typically long (3–10 meters of copper tubing)
The coil is directly connected to high-voltage output (up to 550V) and is not isolated from the grid
In vacuum applications, the coil may cause glow discharge, so insulation is critical (high-temp tape, ceramic mud, varnish, or shielded enclosure required)

Model	Input Power	Output Voltage	Input Power Supply	Output Oscillation Frequency	Load Duration Rate
GWDL-15	15KW	70 - 520V	Three - phase 380V, 50 or 60HZ	200HZ - 20KHZ, determined by customer workpiece heating requirements	100%, 24 - hour continuous operation capability
GWDL-25	25KW	70 - 550V
GWDL-35	35KW
GWDL-45	45KW
GWDL-70	70KW
GWDL-90	90KW
GWDL-110	110KW
GWDL-160	160KW
GWDL-240	240KW
GWDL-300	300KW
GWDL-500	500KW

Induction Heating Resonance Circuit