Overexcitation
A condition where core flux exceeds design level due to excessive voltage or reduced frequency.
Overexcitation occurs when V/Hz ratio exceeds design value, causing core flux toward saturation. Results from excessive voltage, reduced frequency, or both.
Effects: magnetizing current increases dramatically with harmonics, core losses increase causing overheating, stray flux causes eddy heating in tank, abnormal noise.
IEEE/IEC define capability curves (typically 110% V/Hz continuous). Protection (ANSI 24) trips before damage. GSU transformers particularly vulnerable during load rejection.
QDTB designs with appropriate overexcitation margins and specifies protection settings.
Related Products
Related Terms
Magnetic Core
The laminated silicon steel assembly providing a low-reluctance path for magnetic flux, backbone of transformer operation.
Frequency (Hz)
The number of AC cycles per second (50 or 60 Hz), determining transformer design parameters.
EMF (Electromotive Force)
The voltage generated by electromagnetic induction in a transformer winding, proportional to flux change and turns.
More Terms Starting with “O”
Oil-Immersed Transformer
A transformer using mineral oil as insulation and cooling medium, most common for outdoor power and distribution.
On-Load Tap Changer (OLTC)
A device changing transformer tap positions under load without interrupting supply for automatic voltage regulation.
Oil Preservation System
Equipment preventing moisture and oxygen from entering transformer oil, including conservators and sealed tanks.
ONAN Cooling
The simplest transformer cooling method using natural oil circulation and natural air convection, requiring no pumps or fans.
More in “Operating Conditions”
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