ABSTRACT
This chapter describes the permitted magnetic loads of constructional parts, from the point of view of possible local excessive heating. In large electric machines and power transformers, and elements of switching stations, a local excessive heating hazard of constructional parts can appear, due to eddy currents induced by concentrated alternating magnetic field. For instance, a change of positioning of the bolted joints of the cover with the tank changes the overheating hazard of joint bolts in a remarkable way. The temperature method gives the possibility to measure the magnetic field intensity on the body surface in a very short time without the need to heat the object. Elimination of the possibility of local excessive heating can be achieved by the removing of both causes and effects of heating. Thermal effects of local concentration of power losses can be decreased by corresponding heat evacuation to less endangered spots.
