Output increase of existing systems using medium frequency or mains frequency are possible in the range up to 10%, although a basic requirement is a water recooling system of adequate size. Changing the voltage at the coil by 5% while maintaining the same frequency produces an output increase of approx. 10%. Most transformers have +/- taps. Condensers are voltage-stable to approx. + 5%. A reduction of the frequency by approx. 8% at the same voltage will give an output increase of approx. 10%. At the same frequencies and coil voltages, output increases can also be obtained by altering the number of windings.
In the case of a mains frequency for example, the induction coil has 25 windings and a length/height of approx. 1000 mm. If the number of windings is now reduced by 1 winding to 24 windings while maintaining the same coil length/height, the electrical output will be increased by approx. 8%. If the length of the coil is also reduced, the output will be increased by approx. 4%.
The total wall thickness from the new lining to the coil diameter at the copper winding determines the coupling. If the wall thickness of an induction furnace is reduced by 1 mm, this will give an output increase of approx. 0.8%, for the same frequency and voltage. An increase in diameter of 10 mm will therefore give an output increase of approx. 4%.
In mains frequency systems, an output increase of up to 10% may also be possi- ble by means of over-compensation by the condenser bank and the associated capacitive voltage transformation.