Possible causes of transformer overheating: 1 The selection is too high, resulting in core heating (check under no-load if the core is indeed hot); 2 The selection is not high, but the core itself has large high-frequency loss, leading to core heating (check under no-load if the core is indeed hot); 3 The line current density is too large, causing winding heating. If the core is not hot under no-load, then it should be due to excessive winding current density, of course excluding the possibility of high-frequency harmonics generated by distributed parameters causing core heating; 4 The winding current density and core △B selection are both inappropriate, resulting in both winding and core heating. 5 In step-up transformers (output high voltage),...