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Electrical Theory & Applications for HVACR
Glossary
Page 129
counter electromoƟve force
acƟon that takes place in motors when voltage (EMF) is self‐ induced in the rotor conductors which is
opposite of the source voltage
covalent bond
atoms joined together to form a stable molecule by sharing electrons
current
movement of electrons in a conductor, usually expressed in amperes; symbol is I (for intensity)
current relay
a relay operated by the starƟng current of a motor; allows the start winding to drop out of the circuit
aŌer the motor starts
cycle
the voltage generated by the rotaƟon of a conductor through a magneƟc field, from a zero reference
in a posiƟve direcƟon, back to zero in a negaƟve direcƟon; one complete cycle equals 360 degrees of
rotaƟon
cycles per second
the number of alternaƟng current waves in one second of current flow
D
data plate
equipment idenƟficaƟon label, usually containing informaƟon such as model, serial number, voltage,
and amperage
dead
describes a porƟon of a circuit with no voltage
dead leg
the grounded phase of a three‐phase delta wound transformer
dead short
a very low‐resistance connecƟon that allows the unrestricted flow of electrons
dedicated circuit
a circuit that is fused and supplies power to one appliance only
de‐energize
to stop electron flow to a device or open a circuit
delta transformer
a three‐phase transformer that has the finished end of one winding connected to the finished end of
a second winding; configuraƟon resembles the Greek leƩer delta (Δ)