How Efficient is Your Heat Induction Machine?

Induction heating transfers power directly to the part being heated, avoiding heat loss in the surrounding work environment. This efficiency saves energy expenses and allows for faster time to temperature.

It is also easy to control. You can quickly heat a part to your desired level and stop, which is hard to do with competing technologies.

How It Works

Induction heating is an energy-efficient alternative to traditional batch ovens. The induction system uses an electromagnetic field to directly heat the work piece, bypassing the need to heat air or other materials that are not being processed (known as joule loss). The induction process can also be used with non-conductive parts such as glass and plastics (provided they contain a ferromagnetic component such as silicon or graphite) and even reactive metals like titanium and aluminum.

In a typical induction heating system, an electronic oscillator generates a rapidly alternating magnetic field that penetrates the object to be heated. This creates electric currents inside the conductor called eddy currents, which generate heat by the Joule effect. Additional heating occurs through magnetic hysteresis losses in ferromagnetic materials, like iron. The alternating current frequency and the work coil design are key elements in optimizing the power density and penetration depth.

The ability to rapidly direct the alternating magnetic field to the workpiece eliminates heat generation in the surrounding areas of the workpiece, which allows for very short heating times. This is especially important in applications where the object may be moving or changing shape during heating, as it reduces heat loss and damage to the product.

The eddy currents generated by the rapid magnetic field are very small compared to the size of the material being processed. This makes induction very suitable for applications where high precision and fine control of temperature are required. The sensitivity of induction to the size and shape of the object being heated is known as its spatial frequency.

The induction power supply is optimized to achieve a critical frequency with minimized eddy currents and hysteresis losses. This results in the most efficient use of power. The optimum frequency is determined by the work coil, material type, and coupling between the work coil and the workpiece. For example, carbon – although it is a non-metal – is easier to heat than stainless steel with the same frequency. This is because carbon has a much lower resistivity than metals and requires less energy for a given volume of material to be heated.

Power

Unlike other heating methods that introduce heat into the surrounding environment, induction machines direct all of their energy to directly heating the part. This results in minimal wasted energy, which saves energy expenses. In addition to reducing power consumption, this approach provides greater process control. The ability to control the exact amount of energy needed is a major benefit for many industrial applications.

To achieve this precision, induction machines convert utility-frequency AC power into higher-frequency alternating current that is delivered over a custom-designed cable to the workhead. The power supply also contains a bank of capacitors and a custom-designed work coil that combine to create an electromagnetic field that is precisely focused on the workpiece. When the power is applied, the magnetic field induces eddy currents in the metal part that cause it to quickly heat up. Water cooling is usually required to cool the work coil and power supply.

The power supply needs to be matched to the impedance of the workpiece to ensure that maximum current and voltage values do not exceed their safe limits. This can be accomplished by using an impedance-matching circuit in the power supply or with a series of resistors and capacitors. The capacitors must be selected with a low voltage drop and on-state resistance so they will not overheat from the large currents used at the high frequencies. IGBTs are generally chosen, but MOSFETs can be used depending on the application.

As a general rule, magnetic materials heat more efficiently using induction than non-magnetic materials because they generate eddy currents that quickly heat the workpiece. The hysteretic heating method of induction works best on conductive metals like steel. The critical induction frequency depends on the specific material but is often around a Curie temperature of 600degC for carbon steel.

Temperature

The temperature needed for your induction heating process depends on the material you’re working with and the desired heating depth. Conductive materials like metals can be heated directly with induction, while non-conductive materials must be coupled with a susceptor. Conductive and magnetic materials heat quickly, requiring less power, while non-conductive materials require more power and have slower heating rates.

The amount of time it takes for a metal to reach the target temperature determines the energy required and the induction heating efficiency. The deeper you want the heating to penetrate, the longer it will take. Fortunately, induction machines can be configured with adjustable frequency and power to accommodate your processing needs.

Induction equipment can provide precise and uniform heat distribution in just seconds, allowing for quicker cycles. This precision allows you to reduce scrap rates and increase productivity. Induction heating is ideal for industrial processes that require exact temperatures, including brazing, annealing, tempering, and hardening.

With induction, you only use power when you need to heat your workpieces, saving on electricity costs. Induction also uses fewer resources, such as air or water cooling, than furnaces and ovens.

The power supply that drives the induction system is a major contributor to overall machine efficiency. It is important to ensure that you have the correct size power supply to meet your requirements for your application.

Another major factor in heat induction machine efficiency is the coil design. It is necessary that the coils be designed for a specific application to prevent waste of power. A poorly designed coil can produce inefficient magnetic fields and generate too little current.

Using a free online tool to calculate your power usage will help you determine the best configuration for your induction heating application. The calculator lets you input your material, coil specifications, and power requirements to calculate critical factors, such as power density and heating time. The tool can also help you optimize your coil dimensions and geometry to reduce manufacturing costs. For example, you can use the tool to determine if a flexible coil is right for your application or if you need a rigid one with a specific geometry.

Cooling

Induction heating is a fast, efficient, and precise non-contact method of heating conductive materials such as metals and semiconductors. It also allows for precision temperature control, which is critical to many industrial processes such as brazing, hardening, annealing, soldering, and more. The ability to precisely control the electromagnetic field’s power, frequency, and duration enables precise temperature profiles for specific applications, leading to better product quality and efficiency in manufacturing processes.

The power supply is a key component to the operation of an induction heating machine. The power supply converts DC current into alternating current that is fed into the induction coil. Typically, the coil is custom-designed to give your application the right heat pattern and maximize the efficiency of the power supply’s load-matching system.

Once the power supply is properly tuned, induction heating can be a highly repetitive process once the initial setup is complete. This translates to reduced downtime and improved productivity and can help automate welding, brazing, and soldering processes.

A major source of energy loss in an induction heater is cooling the induction coil to keep it from melting, which requires a significant amount of electricity. The cooling systems in an induction power supply can use air, liquid, or passive cooling methods. Air cooling performs the least well in cost, uniformity, and efficiency.

The power supply’s transformer is another large source of energy loss in an induction heating system. While the rotor, stator, and shaft can be cooled using air, liquid, or passive cooling, it’s best to utilize water because of its high efficiency and low operating costs. Water cooling also ensures the power supply is operating within safe temperature ranges and helps prevent any damage from overheating. Overall, an induction heating power supply’s power losses are minimal, and compared to the power lost in a traditional heater band, they can be up to 95% more efficient. That translates to a reduction in energy consumption and lower utility bills for your business.