Induction heater

An induction heater is a key piece of equipment used in all forms of induction heating. Typically an induction heater operates at either medium frequency (MF) or radio frequency (RF) ranges.

Four main component systems form the basis of a modern induction heater

How it works
Induction heating is a non contact method of heating a conductive body by utilising a strong magnetic field. Supply (mains) frequency 50 Hz or 60 Hz induction heaters incorporate a coil directly fed from the electricity supply, typically for lower power industrial applications where lower surface temperatures are required. Some specialist induction heaters operate at 400 Hz, the Aerospace power frequency.

Induction heating should not be confused with induction cooking, as the two heating systems are mostly very physically different from each other. Notably, induction heating (aka forging) systems work with long metallic rods and sheets to bring them up to temperatures as high as ~2500c for work to be done on them.

An induction heater typically consists of three elements.

Often referred to as the inverter or generator. This part of the system is used to take the mains frequency and increase it to anywhere between 10 Hz and 400 kHz. Typical output power of a unit system is from 2 kW to 500 kW.

This contains a combination of capacitors and transformers and is used to mate the power unit to the work coil.

Also known as the inductor, the coil is used to transfer the energy from the power unit and work head to the work piece. Inductors range in complexity from a simple wound solenoid consisting of a number of turns of copper tube wound around a mandrel, to a precision item machined from solid copper, brazed and soldered together. As the inductor is the area where the heating takes place, coil design is one of the most important elements of the system and is a science in itself.

Radio frequency (RF) induction generators work in the frequency range from 100 kHz up to 10 MHz. Most induction heating devices (with induction frequency control) have a frequency range of 100 Hz to 200 kHz. The output range typically incorporates 2.5 kW to 40 kW. Induction heaters in this range are used for smaller components and applications such as induction hardening an engine valve.

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