Induction Heating Power Calculation Formula

[Nadal Braymiller]

Takepaper pulp rotary drum dryer as an example:

To produce 100kg paper each hour, paper moisture content 50%, heating time 120C;

100/0.5=200kg, that means to heat 100kg paper from room temperature to 120C and 100kg moisture needs to be evaporated, so that induction heating power calculation for rotary drum dryer needs to be divided into two steps.

The power of the induction melting furnace is an important indicator to measure the heating capacity of the induction melting furnace, and to a certain extent determines the heating speed and heating temperature of the induction melting furnace.

So, how is the power calculation of the induction melting furnace calculated?

What problems should be paid attention to in the power design of induction melting furnaces?

The power grid stipulates that for transformers with a capacity of 200KVA or more, the power factor below 0.9 will be fined step by step, and the power factor above 0.9 will be rewarded step by step. This means that the lower the power factor, the more fines, and the higher the power factor, the higher the reward, up to 0.95.

The power factor of the medium frequency is generally around 0.78, and contains 2-7 harmonics. When the theoretical calculation is compensated until the power factor is 1, 188KVAR reactive power compensation equipment is required. The actual design selection can be selected between 150-200. In addition, the traditional Capacitor bank compensation is easily damaged due to harmonic problems under this working condition, and adding a reactor can only filter out a single harmonic, and the filtering effect is not good. It is recommended to use a low-voltage SVG to filter out harmonics while compensating reactive power.

What is the power of a 3-ton intermediate frequency furnace?

The power of 3T is generally around 2500kw, and the melting material is steel. If you are using other materials, you can call us directly for a consultation. The melting time is about 70 minutes per furnace.

The intermediate frequency power is the output power of the inverter, and the measurement is the power of the load (that is, the intermediate frequency quenching furnace if there is an output transformer, including the loss power of the output transformer).

The DC voltage is multiplied by the DC current to calculate the DC power. In addition to the intermediate frequency power, the DC power also includes the loss of the filter element (reactor or DC filter inductor), inverter thyristor or IGBT element, and the connecting busbar from the intermediate frequency output to the load.

So the intermediate frequency power is always smaller than the DC power. However, for a good intermediate frequency power supply, the difference between them (or the loss of the power supply) is not large, and it is reasonable within 5%.

For all induction heating applications where workpieces of specific size and mass need to be heated to a specific temperature in a required period of time, you can use the formula below to calculate the approximate power of the generator required:

When an electrically conductive body is placed in the region of a time varying magnetic field, electric currents are induced in the body causing thermal power generation in the body. This effect, known as induction heating, is widely used in industries ranging from the production of optical glass fiber to the heating of 25 tonne steel slabs [examples are given in BNCE (1984)]. The magnetic field is produced by a suitable arrangement of conductors, the induction coil, connected to a source which can provide the required time varying current in the coil. Electrical power supplied to the coil is thus converted to thermal power in the workpiece through the electromagnetic field, without physical electrical connection to the workpiece. Almost invariably, power sources used for induction heating provide an alternating current to the induction coil, the choice of frequency being critical to the particular heating application.

For a solid circular billet of diameter d and length L, heated in an enclosing circular coil of diameter D, length Lc and having N turns with a current of I amp/turn, the induced power Pw is approximately given by:

where Qrod is given in Figure 1 as a function of d/δ, and Kc is dependent on the ratios d/D, d/δ and L/Lc. Orfeuil (1987) gives empirical values for Kc, which tend to unity as d/D and L/Lc approach unity. The power induced in hollow cylinders of wall thickness t is calculated with Qrod in the above expression replaced by an equivalent flux factor Qcyl, which is a function of t/d, d/δ and μr independently of δ. Davies (1990) shows graphs of Qcyl for a range of these parameters.

where Q is the relevant flux factor, KA is the space factor of the coil system and SC/SW is the ratio of the coil perimeter to that of the workpiece in the same plane. Harvey (1976) shows that coil efficiency can be significantly increased by the use of multilayer windings instead of the more conventional single-layer coil. These high-efficiency coils are now commonly used for heating nonferrous billets at mains frequency.

The overall efficiency of induction heating is ηsupplyηthermalηc ηsupply is typically 0.8-0.9 (per unit) and accounts for losses in cables, power factor correction capacitors and frequency conversion equipment; the thermal efficiency, ηthermal, represents thermal losses from the workpiece and is critically dependent on operating temperature, thermal insulation and method of operation of the heater. Typical values are in the range 0.7-0.9 (per unit).

Transverse flux induction heating is employed for heating continuous metal strips. In this mode, the magnetic field is directed at the broad face of the material rather than through its narrow cross-section, with the induced current flowing across the width of the strip. The advantages of the method include a higher efficiency, particularly for nonferrous strips, at much lower operating frequencies than are possible with conventional axial flux induction heaters. Ireson (1989) gives a useful overall account of the technique and its commercial realization.

Apart from mains frequency installations, power supplies for modern, induction heaters are derived from solid state frequency converters. Unit sizes up to 7 MW have been installed for metal melting at 1-3 kHz and I MW units are now available for frequencies up to 500 kHz, previously the domain of power vacuum tube triodes.

Induction heating is a process for heating metals and other electrically-conductive materials that is precise, repeatable and a safe non-contact method. It involves a complex combination of electromagnetic energy and heat transfer that passes through an induction coil, creating an electromagnetic field within the coil to metal down materials. Materials such as Steel, Copper, Brass, Graphite, Gold, Silver, Aluminum, and Carbide can be heated for a range of applications, which include various heat treating applications such as hardening, annealing, tempering, brazing, soldering, shrink fitting, heat staking, bonding, curing, melting and many more.

ii. Induced heat. When an electrically conductive material is exposed to an alternating magnetic field, depending on the material, heat is induced by two mechanisms; Joule Heating and Magnetic Hysteresis. The latter occurs in the magnetic metals (such as Carbon Steel below Curie temperature) in which the rotation of the adjacent magnetic dipoles due to the direction change of the imposed magnetic field will lead into friction and heat. This effect increases by increasing the frequency of the imposed magnetic field.

Joule Heating is the main heating effect caused by induction phenomenon. Any current I, ac or dc, passing through an electrically conducting material causes voltage drop V resulting in energy conversion to heat. Heat power is defined by V.I=R.I^2, where R is the electrical resistance of the current path. The resistance of the current path is inversely proportional to the cross-section area in which the current is flowing.

Using high frequencies in induction heating industry (Mainly 10kHz to 700kHz) implies very thin penetration depths in metals (typically less than 1mm). Passing high current density (big I) through that shallow depth (big R) results in high R.I^2. Consequently, high energy conversion from electrical to heat occurs.

By following these steps and considering the key factors, you can accurately calculate the induction heating power required for your specific application, ensuring efficient and effective heating of the material.

Induction heating is a process in which an alternating electrical current is passed through a conductive material, generating a magnetic field. This magnetic field induces eddy currents in the material, which then causes it to heat up due to resistance.

The main factors that affect induction heating calculations include the frequency and magnitude of the current, the electrical conductivity and magnetic permeability of the material, and the geometry and size of the heating coil.

To calculate the heating time for a specific material, you will need to know its electrical resistivity, specific heat capacity, and initial and desired final temperatures. These values can be used in the appropriate equation to determine the required heating time.

A single-turn heating coil is a simple, circular loop of wire, while a multi-turn heating coil has multiple loops or turns. Multi-turn coils are more efficient for heating larger volumes of material, while single-turn coils are better for smaller or more precise applications.

Induction heating calculations can be used for most conductive materials, including metals and some non-metals. However, the effectiveness of induction heating may vary depending on the electrical and magnetic properties of the material.

Induction heating involves passing an alternating electrical current through a copper coil, creating a magnetic field that induces eddy currents in the metal object placed within the coil. These eddy currents generate heat, causing the metal to reach its melting point.

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