Electrical Flashcards
Resistive resistance is:
Resistance that remains constant.
Reactive resistance is:
Resistance found in devices with a magnetic coil, which creates a magnetic field in direct opposition to the volt, creating back-emf.
Emf:
Electromotive force
Ohms law:
E=I×R, the relationship between Volt, Current and Resistance
Continuity
Describes a complete path for electron movement from one point to another.
Power equation
P= IxE watt=amp x volt
Voltage drop (VD)
The loss of emf (volt) between 2 wires or across a load.
Causes of VD
An electrical load, loose wire or undersized conductor.
Ampacity
The amount of current a conductor can safely carry with out overheating.
Volt and resistance determine the mount if electron flow. Watt measures. . .
The rate of energy conversion
Self Inductance
When varying lines of magnetic flux induce an EMF in a coil, the coil has self inductance.
Mutual Inductance
When varying lines of magnetic flux induce an EMF in an adjacent coil, the coils have mutual Inductance. Based of transformers.
Inductive Reactance
A type of resistance that us produced when a coil of wire carries an alternating current.
LRA
Locked Rotor Amp, the amp draw of a motor on start up
FLA
Full Liad Amp, the Amp draw of a motor at peak torque and hp. Full load.
RLA
Rated Load Amp, the Amp draw of a compressor when operating at its rated load, rated voltage and rated frequency.
Resistance is used to measure for
An electrical short
A grounded connection
An open
A higher than normal resistance
Capacitors are rated in
Farads/ microfarads
Define power
The rate at which work is being done
True power
The amount of power actually used by a load (W)
Reactive power
The power absorbed and returned by the circuit without doing any useful work. (VAR)
Apparent power
The total power (True + Reactive) in the circuit (VA)
Inductive reactance
Resistance caused by magnetic fields, like a motor
Capacitive reactance
Resistance caused by the shortage of electrons
Power factor
PF = True power (W) / Apparent Power (VA)
The lower the power factor, the greater the amount of current that must be carried to handle the load.
Phase splitting
Start and run windings have diff Inductance values, the current flowing through the start winding is out of phase with the run winding, split phase causes a rotating magnetic field in the stator causing the rotator to start turning.
Split phase motor
A single phase induction motor used in applications that operate in the fractional hp range
Variable Frequency Drive (VFD)
Control circuit that modifies the frequency of signals to ac motors.
Uses a rectifier to change 60hz ac to DC then back to AC at a different frequency.
An electrical property that opposes the current change in an AC circuit.
Inductance
When too much current flows through an electrical circuit.
Overload
A unit of electrical power, equivalent to the watt.
Volt-amp (VA)
Thermistor
Regulates the flow of current by changing its resistance based on heat.
Bonding
A continuous electrical connection of all the metal parts in an electrical system.
Short circuit
When current is unintentionally routed around a component or load instead of through it.
Diode
A solid state device that allows DC current to flow in one direction.
Anode
The positive side of a diode
Cathode
The negative side of a diode
Transducer
A device that converts the input signal from one form of energy to an output signal of another form of energy
Diac
A diode for AC, allows current to flow in both directions
Rectifier
An electronic circuit that converts AC to DC
Inverter
Converts DC to AC
Thermistor
A solid state device that changes its resistance as the temp of the thermistor changes.
NTC vs PTC
Negative temp coefficient= thermistor decreases resistance as temp increases
Positive temp coefficient = thermistor increases resistance as temp increases.
