The power unit (often called the inverter) is used to change the frequency of the incoming 3 phase mains supply (normally 50Hz to 60Hz) to a higher frequency output typically between 1kHz to 12mHz.
This higher frequency energy is fed to a work-head, which by utilisation of capacitors and transformers matches the output impedance of the power unit to a suitable inductor. This generates a large AC current flow and therefore a strong magnetic field within the inductor. On introduction of a suitable work piece to the magnetic field the principle of electromagnetic induction creates a current flow within the work-piece, this in combination with the resistance of the material causes an electrical loss which is expressed as heat. In magnetic materials below their curie point hysteresis losses also add to the heat generated.
The diameter, number of turns and geometry of the coil will affect the efficiency of the process and heating pattern. When the unit is to be operated manually it is advisable to design the coil in such a way as to reduce the output voltage below levels which are acceptable under the EWR (Electrical Wire Routing). When using a single turn coil (low voltage) the coil can be made from solid copper and machined making a coil less vulnerable to damage.
In melting, mass heating and forging applications it is not unusual to use multi turn coils. Due to the voltages produced in this type of coil, output terminals and the coils themselves will need to be suitably insulated. Normally the coil turns will be insulated and varnished to prevent flashovers between turns, in certain applications further protection will be provided by a refractory lining. The lining also offers protection to the turns form the high temperature component as well as limiting the radiated losses.
Induction heaters available in a range of frequencies to suit the whole range of applications typically frequencies of 1kHz up to 10kHz are used for forging melting and deep case hardening in the 3mm to 6mm ranges. Higher frequency equipment in the 30kHz to 200kHz range are used for shallower cases in the 0.5mm to 2mm range and also for brazing, shrink fitting and small diameter forging work.
It is usual for the larger power units in the 50kW to 500kW range to run at the lower frequency range, say 1kHz up to 10kHz, and the smaller units from 1Kw output up to 100Kw to operate at the higher frequencies of 30kHz to 300kHz.
Systems are available which can run at both high frequency and powers say 500kW at 200kHz as are units which run at frequencies into the mHz however these are normally for specialist applications such as plasma generation and high volume strip heating.
Please browse our website for more information about Induction Equipment Installation then contact us on 0114 272 3369 to speak to a member of our team or e-mail us on firstname.lastname@example.org.