RLC + Power Flashcards

1
Q

How do you calculate True Power?

What is True Power?

A

Irms^2 * R

Power dissipated by the resistor

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2
Q

How do you calculate reactive Power?

What is reactive Power?

A

Power stored and released by the capacitor or inductor

Irms^2 * XL or Irms^2*Xc

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3
Q

How do you calculate apparent Power?

What is apparent Power?

A

Phasor sum of Reactive and True power

Irms^2 * Z
Vrms * Irms

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4
Q

How do you calculate Reactive Power and True power form apparent power?

A
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5
Q

What is the Unit of True power

A

Watts

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6
Q

What is the unit of Apparent Power

A

VA (Volt ampare)

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7
Q

What is the unit of Reactive power

A

VAR (volt ampere reactive)

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8
Q

Derive the Transient response Differential Equation for an RLC circuit

Explain the solution

A

Solution has two parts the transient and steady state response.

i = i(transient) + i(steady state)

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9
Q

Explain the Characteristics of an Underdamped responce

A

LCR circuit experiences decaying oscillations (ringing) at the natural frequency of the system

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10
Q

Explain the Characteristics of an overdamped response

A

response has a peak and a decaying exponential

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11
Q

Explain the Characteristics of a critically damped response

A

responce has a peak and exponential that decays to zero in the shortest possible time

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12
Q

Explain how the solution to the LCR transient response differential equation can tell you if a system is over, under or critically damped.

A
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13
Q

why can we ignore the steady state response in an RLC circuit?

A

capacitor prevents current flowing in this condition.

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14
Q

explain how to calculate the impedance of an RLC circuit that is connected to a sinusoidal voltage and the phase angle

A
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15
Q

calculate the peak current and phase angle of the following circuit,

A
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16
Q

Explain what is meant by series resonance in a LCR Circuit

When does this Occur
What is the impedance at resonance
what is the frequency which resonance happens

A

Due to the Capacitor and inductor connected in series there will be a frequency where the current increases to a peak value.

17
Q

Explain the conditions needed for a LCR circuit to be at resonance

What frequency does this occur at

A

Impedance of Inductor = Impedance of Capacitor

therefore
V(inductor) = V(Capacitor)
V(resistor) =V(supply)

18
Q

How do you derive the formula that calculates the frequency for resonance of a series RLC Circuit?

A
19
Q

Explain why Apparent Power is equal to true Power at resonance of a series RLC Circuit?

A

Reactive Components cancel out at resonance
Phasor sum of 0 and True power = True power

20
Q

Draw the Phase Diagram of an LCR Circuit

A
21
Q

What is Q Factor

A

Ratio of Reactive Power in Capacitor or inductor

and average power in the Resistor

22
Q

What does a High Q Factor imply

What does a Low Q imply

A

Sharp Resonance Peak with Narrow Width

Broad Resonance Peak with wide Width

23
Q

What is Q Factor in terms of energy

A

Ratio of Energy stored in the Circuit

and the energy dissipated per cycle

24
Q

How does Q Factor Impact the damping of the transient state

A

High Q factor means the circuit is less damped

Sustains oscillations for a longer period of time

Low Q factor means the circuit is more damped

Oscillations Decay More Quickly

25
Q

Derive an Equation for Q Factor in terms of Resistance Inductance and Capacitance

A
26
Q

Explain why care must be taken with RLC circuits at resonance

A

Voltage across inductor and capacitor is the same

Both can go much higher then the voltage supply at resonance

27
Q

What is another formula for Q Factor in terms of bandwidth

A
28
Q

What is the Bandwidth in a LCR circuit

How do you calculate the bandwidth.

A

the difference between the two values of apparent power that equal 1/2 of the power of the resonant peak.

Reduce the current by a factor of root(2), or reduce impedance by a factor of root(2)

29
Q

Derive how to calculate Bandwith from an RLC Circuit.

A
30
Q

Draw a Bandpass Filter using a Capacitor and inductor

A
31
Q

Draw a bandstop filter using a capacitor and inductor

What does a band stop do?

A

Sharp decrease of current near a specific frequency

32
Q

How do you calculate the Voltage across a Band pass filter made from Capacitors and Inductors

A
33
Q

Draw a Tank Circuit

Explain the what happens

A

Capacitor charges Up

Capacitor discharges

Inductor magnetic field strength increases, applied in the opposing direction to current flow

The inductor magnetic field applies to oppose the current dropping to zero, in turn charging the capacitor .

Capacitor discharges , but sending current in the opposite direction to as before.

Repeat Steps 3,4

This whole process then repeats

34
Q

What happens to a tank circuit at resonance

A

it draws no current for the power supply

effectively becoming a brick wall. where no current can pass through

Infinite resistance

35
Q
A