unit 4 Elec Principles hv

Three-phase voltages are _____ out of phase with each other.

120 degrees

The horsepower rating of three-phase motors and the kilovolt-ampere rating of three-phase transformers are about _____ greater than for single-phase motors or transformers with a similar frame size.

150 percent

Because inductive reactance and capacitive reactance are _____ out of phase with each other, they subtract from each other in an AC circuit.

180°

In a circuit containing a capacitor, the impressed voltage is _____ with the applied voltage.

180° out of phase

In a balanced three-phase system, the conductors need be only about _____ the size of conductors for a single-phase, two-wire system of the same kilovolt-ampere (kVA) rating.

75 percent

When a capacitor is connected to a(n) _____ circuit, current appears to flow through the capacitor.

AC

Each complete wave form of 360° is called A.

Cycle

Frequency is measured in

Hertz

The symbol XL stands for _____.

Inductive reactance

What is the unit for capacitive reactance?

Ohms

The quality of a capacitor is found by Q = _____.

R/XC

When a capacitor is connected in a circuit with a resistor, the amount of time needed to charge the capacitor is called the _____.

RC time constant

the square root mean of the square of instaneous current is known as the

RMS

What type of load contains pure resistance?

Resistive

Of the different power values in an RC circuit, which is known as apparent power?

VA

The power in a capacitor is reactive power. What is the unit for reactive power?

VAR

If a three-phase load is a pure reactive load, then the power calculated has units of _____

VARs

The symbol for reactive power of an inductor is _____.

VARs

What is the symbol for capacitive reactance?

XC

The symbol for reactance is _____.

XL

What is a device that opposes a change of voltage?

a capacitor

Variable capacitors normally have a dielectric of ____

air

In a capacitor, the voltage difference between the plates controls the _____.

amount of dielectric stress

if an Ac waveform is rectified and converted into DC, the voltage that results is ----- value

average

The difference between the two frequencies at which the current is 0.707 of the maximum current value is the _____.

bandwidth

Nonpolarized capacitors _____.

can be used with either AC or DC

Countervoltage presented by a capacitor is called _____.

capacitive reactance

Dividing a circuit's total applied voltage by the total impedance results in the total _____.

current

In a RLC series circuit, _____ is the same through all components and the _____ are out of phase.

current; voltages

A three-phase connection in which three separate inductive loads have been connected together is a(n) _____ connection.

delta

Line voltage and phase voltage are the same in the _____ connection.

delta

A HIPOT is a test set used to test capacitor _____.

dielectric

The material between a capacitor's plates is rated by a value called the _____.

dielectric constant

A term used to indicate the same value as the r m s value is the ____ value.

effective

Polarized capacitors are also known as _____ capacitors.

electrolytic

Energy in a capacitor is stored as a(n) _____.

electrostatic charge

Capacitors charge and discharge at a(n) _____ rate.

exponential

What letter symbolizes the farad?

f

t/f, both AC and DC can be transformed.

false

What is the basic unit of capacitance?

farad

A charge curve for a capacitor is divided into _____ time constants.

five

the number of cycles completed in one second is called a

frequency

The unit of inductance is the _____.

henry

The total current-limiting effect is called _____.

impedance

When current rises and falls at the same rate as the voltage and reverses the direction of flow when the voltage reverses polarity, the current is said to be _____ with the voltage.

in phase

Increasing the surface area of the plates will cause the capacitance of a capacitor to _____.

increase

When a magnetic field continually changes magnitude and direction, a voltage is continually being induced in the coil. This voltage is called _____ voltage.

induced

Circuits are generally considered to contain _____ when any type of load that contains a coil is used.

inductance

The capacitive reactance of a capacitor is _____ proportional to frequency.

inversely

If a RLC series circuit contains more inductive VARs than capacitive VARs, the circuit has a _____ power factor.

lagging

If the voltage in a RLC series circuit is ahead of the current, the power factor is referred to as _____.

lagging

In a pure inductive circuit, current _____.

lags voltage by 90°

If a RLC series circuit contains more capacitive VARs than inductive VARs, then the circuit has a _____ power factor.

leading

If the current leads the voltage in a RLC series circuit, the power factor is referred to as _____.

leading

If the voltage is behind the current in a RLC series circuit, the power factor is referred to as _____.

leading

In a pure capacitive circuit, the current _____ the applied voltage by _____.

leads; 90°

In some capacitors, there is a small amount of current that flows from one plate, through the dielectric material to the other plate. This current is called _____ current.

leakage

The alternator must supply the _____ for each of the loads.

line current

In a three-phase connection, what is the voltage measured between the lines?

line voltage

What type of AC waveform features voltage rising at a constant rate with respect to time?

linear

The JAN standard is used to mark a capacitor intended for _____.

military

In a three-phase circuit, the true power (watts) is found by _____.

multiplying apparent power by the power factor

Polarized capacitors _____.

must be used with DC only

In three-phase power systems, the delivered power _____.

never falls to zero

When calculating the power of a pure resistive load, the voltage and current are in phase with each other and the power factor is _____.

one

square waves are generally produced by electronic devices called

oscillators

the maximum point of a waveform is called the

peak

In a three-phase connection, what is the voltage measured across a single winding?

phase voltage

A capacitor is constructed by separating two metal conductors known as _____ with an insulating material known as a(n) _____.

plates; dielectric

The _____ of a circuit is the cosine of the phase angle.

power factor

The amount of resistance compared with the inductive reactance determines the _____ of the coil.

quality (Q)

The current-limiting property of an inductor is called _____.

reactance

Volt-amperes-reactive is used to measure the _____ in a pure inductive circuit.

reactive power

In a RLC series circuit, the point at which XL and XC are equal is called _____.

resonance

When AC voltage is rectified and converted into DC, the resulting waveform is normally not pure, flat DC. The pulses that occur are called _____.

ripples

The voltage rating of a capacitor _____.

should never be exceeded

Rotating machines normally produce a waveform called a ---- wave

sine

What is the most common of all AC waveforms?

sine

The_____ effect occurs when AC induces eddy currents into the conductor, which cause the electrons to be repelled toward the outer surface of the conductor.

skin

In a wye-connected system, the line voltage is higher than the phase voltage by a factor of _____.

square root of three

Another name for the three-phase wye connection is the _______________ connection.

star

To help overcome the problem of skin effect in high-frequency circuits, conductors with a large amount of _______________ must be used. surface area

surface area

The _______________ indicates the amount of capacitance change with temperature.

temperature coefficient

In calculating apparent power (VA) in a three-phase circuit, the phase values of voltage and current are multiplied by _____.

three

In a DC Circuit the product of volts times the amperes is called the ---- power

true

In a capacitive circuit, the voltage leads the current by 90 electric degrees.​

true

​In a series RC circuit, total impedance is a combination of resistance and capacitive reactance.

true

Dividing a circuit's total applied voltage by the total impedance results in the total _____.

true; apparent

In an RLC series circuit, the ratio of resistance, inductance, and capacitance determines how much the applied _____ leads or lags the circuit current.

voltage

In a capacitor, the amount of dielectric stress is proportional to the _____.

voltage difference between the plates

What is the unit of measure for the power delivered to the load in a DC circuit?

watts

Line current and phase current are the same in the _____ configuration.

wye

The three-phase connection in which one end of each of the windings are connected together is called a(n) _____ connection.

wye

the amplitude of a waveform is measured from

zero to the highest value obtained in either direction

When the voltage and current have _____ polarities in a pure capacitive circuit, the capacitor is discharging and the energy is returned to the circuit.

​opposite