What Is a Magnetic Yoke in an Induction Furnace?
A magnetic yoke is the laminated silicon-steel limb placed outside the induction coil of a melting furnace. Furnace builders also call the same part a silicon steel column. Its job is magnetic and mechanical at the same time.
Without the limb, leakage flux closes through the steel shell and through nearby steelwork. The shell runs hot, the power supply sees a larger magnetising current, and the coil has less support when the furnace is energised. A high-permeability stack gives that flux a shorter path through the melt. Arc stacking, used on these yokes, keeps the rolling direction of grain-oriented sheet following the coil, so the joint is less likely to saturate in one spot.
The limb also braces the coil. Stainless clamps and through-bolts hold the sheets. On a 60 ton yoke that clamp is ten M20 stainless bolts. On a 5 ton yoke the through-bolts are demagnetised stainless, so the bolts themselves do not become a local flux path.
Heat is the other limit. A stack that is allowed to run hot grows, loosens, and rusts on the cut edges. Water-cooled channels, stainless tanks, embedded copper tubes and embedded stainless tubes are four ways to hold the steel near ambient temperature. Cut edges are coated, on most builds with a DuPont anti-arc insulating coating, and on the 5 ton vacuum-furnace yoke with THERMAL S.C.
If you are specifying a yoke, the useful data are furnace capacity, frequency, power, coil diameter, coil height, number of yokes, cooling method, and a photo or drawing of the existing part. Send those to sales@magneticyoke.com or use the quote form.