Hot-Spot Temperature
The highest temperature within transformer winding insulation, determining aging rate and loading capability.
Hot-spot temperature is the highest temperature within the winding insulation system. Always higher than average winding and top oil temperatures.
Critical for insulation life. Per Arrhenius theory, life halves every 6-8C above rated. For Class A insulation (105C), normal hot-spot limit is 98C for 20-year life.
Calculated: hs = top-oil + H x gradient. Direct measurement via fiber-optic sensors provides most accurate monitoring.
QDTB optimizes cooling duct design to minimize hot-spot gradient, enabling higher loading and extended life. Our cooling designs ensure uniform temperature distribution.
Related Products
Related Terms
Temperature Rise
The temperature increase of transformer components above ambient at rated load, a key design parameter.
Insulation Class (A/E/B/F/H)
Standardized temperature ratings for transformer insulation materials defining maximum operating temperatures.
Cooling Class (ONAN/ONAF/ODAF)
Standardized codes describing transformer cooling methods: O=Oil, N=Natural, A=Air, F=Forced, D=Directed flow.
More Terms Starting with “H”
Harmonics
Integer multiples of fundamental frequency from non-linear loads, causing increased transformer losses and overheating.
Hysteresis Loss
Energy lost in core steel from repeated reversal of magnetic domains each AC cycle, a component of core loss.
HV/LV Bushing
High-voltage and low-voltage insulated conduits for transformer winding connections through the grounded tank.
More in “Performance Parameters”
Core Loss
Power dissipated in the transformer magnetic core due to hysteresis and eddy currents, also called iron loss or no-load loss.
Copper Loss
Power lost as heat in transformer windings due to electrical resistance, proportional to the square of load current.
Efficiency Class (IE1-IE4)
International classification for transformer energy efficiency, IE1 (standard) to IE4 (premium) with progressively lower losses.
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