Excitation Current
Current drawn by transformer primary when energized with no load, consisting of magnetizing and core-loss components.
Excitation current (no-load current) drawn when primary energized at rated voltage, secondary open. Components: magnetizing (Im) establishing flux, core-loss (Ic).
Typically 1-5% rated for distribution, 0.5-2% for large power transformers. Predominantly reactive (80-90 degrees lag).
Non-sinusoidal waveform generates harmonics (3rd). QDTB designs cores to minimize through material selection and precision assembly.
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Related Terms
Magnetizing Current
The reactive component of no-load current establishing magnetic flux in the transformer core.
Core Loss
Power dissipated in the transformer magnetic core due to hysteresis and eddy currents, also called iron loss or no-load loss.
Magnetic Core
The laminated silicon steel assembly providing a low-reluctance path for magnetic flux, backbone of transformer operation.
Harmonics
Integer multiples of fundamental frequency from non-linear loads, causing increased transformer losses and overheating.
More Terms Starting with “E”
Eddy Current
Circulating currents induced in conductive materials by changing magnetic fields, causing energy losses in transformers.
Efficiency Class (IE1-IE4)
International classification for transformer energy efficiency, IE1 (standard) to IE4 (premium) with progressively lower losses.
EMF (Electromotive Force)
The voltage generated by electromagnetic induction in a transformer winding, proportional to flux change and turns.
EV Charging Transformer
A transformer for EV charging stations handling harmonic-rich loads and variable power demands.
More in “Electrical Fundamentals”
Apparent Power (kVA)
The total power in an AC circuit combining real (active) and reactive power, measured in kilovolt-amperes (kVA).
Eddy Current
Circulating currents induced in conductive materials by changing magnetic fields, causing energy losses in transformers.
EMF (Electromotive Force)
The voltage generated by electromagnetic induction in a transformer winding, proportional to flux change and turns.
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