Dictionary of Electrical Engineering
Commonly used terms in the Electrical industry.
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D'Arsenval meter
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a permanent-magnet moving-coil instrument with a horseshoe form magnet. It measures direct current only.
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damper winding
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an uninsulated winding, embedded in the pole shoes of a synchronous machine, that includes several copper bars short-circuited by conducting rings at the ends, used to reduce speed fluctuation in the machine by developing an induction-type torque that opposes any change in speed.
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damping
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a characteristic built into electrical circuits and mechanical systems that prevents rapid or excessive corrections that may lead to instability or oscillatory conditions.
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damping coefficient
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electrical torque component in phase with the rotor speed.
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dB
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See decibel
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dBc
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ratio of the signal power (p) to a reference signal power (pref), usually the modulation carrier signal, expressed in decibels referenced to a carrier (dBc). Thus a harmonic signal that is 1/100th of the power in a desired fundamental signal is at -20 dBc.
PdBd = 10 log10 ( p / pref )
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dBm
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Power ratio in decibels referenced to 1 milliwatt.
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dBW
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ratio of the signal power in watts (p watts)to a 1W reference power, expressed in decibels referenced to 1 W (dBW). Thus
1 watt signal power is equal to 0 dBW, and -30 dBW is equal to 0 dBm.
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DC
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direct current
See DC voltage
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DC block
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A circuit simulation component that behaves like a capacitor of infinite value.