Alternating Current Study Guide. Preface. This module is DIFFICULT.

Preface This module is DIFFICULT. This material will take more effort to understand and more effort to pass than tests from previous modules. This is on par with a college-level electrical engineering course. Let s break the module up into more manageable pieces, prioritize, and eat this elephant

Preface Sine Wave Generation Transformers Sine Wave Terminology and Characteristics Power in AC Circuits - Power Triangle - Power Factor Three Basic Circuit Load types: - Resistance - Inductance - capacitance Combination Load Circuits 35/2 ELI the ICE man

See pages 1 and 2 in the mod text. Alternating Current Study Guide Sine Wave Generation Two principles form the basis of all electromagnetic phenomena: - An electric current in a conductor creates a magnetic field that surrounds the conductor. - Relative motion between a conductor and a magnetic field when at least one component of that relative motion is in a direction that is perpendicular to the direction of the field, creates a voltage in a conductor.

See pages 1 and 2 in the mod text. Alternating Current Study Guide Sine Wave Generation Three factors affect the amount of voltage generated: 1. Strength of magnetic field (typically constant) 2. Length of wire loop (typically constant) 3. Phase angle (always changing) Here is the formula to find the magnitude of voltage at ANY phase angle: E = Emax sin Θ but what is a phase angle.

See pages 1 and 2 in the mod text. Alternating Current Study Guide Sine Wave Generation Here is the formula to find the magnitude of voltage at ANY phase angle: E = Emax sin Θ but what is a phase angle.

See pages 1 and 2 in the mod text. Alternating Current Study Guide Sine Wave Generation Here is the formula to find the magnitude of voltage at ANY phase angle: E = Emax sin Θ Learn how to use Google for calcs: sin 0 degrees sin 30 degrees sin 45 degrees sin 60 degrees sin 90 degrees

See pages 1 and 2 in the mod text. Alternating Current Study Guide Sine Wave Generation Here is the formula to find the magnitude of voltage at ANY phase angle: E = Emax sin Θ So if all the values of sine are fractional except for: sin 90 degrees = 1 sin 270 degrees = - 1 Therefore, the maximum value for voltage will occur at phase angles of?

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Phase Angle (degrees) Frequency (Hz or cps) Amplitude (Volts and Amps) Time (secs) Cycle Period (secs) Alternation Peak (Volts and Amps) RMS (Volts) Average (Volts) Phase: in phase or out of phase

Magnitude of volts or amps See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Y Phase Angle or Time X

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Cycle Alternation Each time a waveform changes from zero to peak and back to zero is called an? Two form a.

Sine Wave Terminology and Characteristics Frequency (Hz or cps) The frequency of a waveform is the number of times per second an identical pattern repeats itself or The number of cycles per second is the frequency What is the frequency of this wave form? In Hz? In cps? 1 sec frequency = cycles See pages 3 thru 6 in the mod text. secs

Sine Wave Terminology and Characteristics Frequency (Hz or cps) The frequency of a waveform is the number of times per second an identical pattern repeats itself. What is the frequency of this wave form? In Hz? In cps? 4 sec See pages 3 thru 6 in the mod text.

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Period The period of a waveform is the time to complete one cycle t = time = period t = 1 cps

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Period The period of a waveform is the time to complete one cycle t = 1 cps

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Period The period of a waveform is the time to complete one cycle t = 1 cps 1.0

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Period The period of a waveform is the time to complete one cycle t = 1 cps What is the period? 1 sec

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Wavelength The wavelength lamba (Λ) is the distance traveled by a waveform during a period. Wavelength? Λ = tc t = 1/60 sec (for AC in United States or 0.0167 sec c = speed of electromagnetic radiation or 3 x 10 8 m/s or? sec 186,000 miles/sec or 9.8 x 10 8 ft/sec

See pages 3 thru 6 in the mod text. Alternating Current Study Guide Sine Wave Terminology and Characteristics Wavelength The wavelength lamba (Λ) is the distance traveled by a waveform during a period. Wavelength? Λ = tc Wavelength: 300,000,000/60 = 5,000,000 m 980,000,000/60 = 16,333,000 ft t = 1/60 sec (for AC in United States or 0.0167 sec c = speed of electromagnetic radiation or 3 x 10 8 m/s or? sec 186,000 miles/sec or 9.8 x 10 8 ft/sec Two wavelengths: 1/30 sec or 0.033 secs

Sine Wave Terminology and Characteristics Peak RMS Average

Sine Wave Terminology and Characteristics Peak RMS Average Average = 0.637 x Peak Peak = Average / 0.637 RMS = 0.707 x Peak Peak = RMS / 0.707 KNOW THESE FORMULAS!!

Sine Wave Terminology and Characteristics Peak RMS Average If Peak-to-Peak is 700V, What is Peak?

Sine Wave Terminology and Characteristics Peak RMS Average If Peak-to-Peak is 700V, What is Peak? 350V If Peak is 350V, what is RMS? Average?

Sine Wave Terminology and Characteristics Peak RMS Average If Peak-to-Peak is 700V, What is Peak? 350V If Peak is 350V, what is RMS? 247V Average? 223V

Sine Wave Terminology and Characteristics Peak RMS Average If Peak-to-Peak is 340V, What is Peak? What is RMS? What is Avg?

Sine Wave Terminology and Characteristics Peak RMS Average If Peak-to-Peak is 340V, What is Peak? 170V If Peak is 170V what is RMS? 120V Average? 108V

Sine Wave Terminology and Characteristics Peak RMS Average If Peak is 392V What is RMS? What is Avg?

Sine Wave Terminology and Characteristics Peak RMS Average If Peak is 392V What is RMS? 277V What is Avg? 250V

Sine Wave Terminology and Characteristics Peak RMS Average If RMS is 200V What is Peak? What is Avg?

Sine Wave Terminology and Characteristics Peak RMS Average If RMS is 200V What is Peak? 283V What is Avg? 180V

Sine Wave Terminology and Characteristics Peak RMS Average If AVG is 300V What is RMS? What is Peak?

Sine Wave Terminology and Characteristics Peak RMS Average If AVG is 300V What is RMS? 333V What is Peak? 471V

Sine Wave Terminology and Characteristics Peak RMS Average If Peak is 150V What Peak-to-Peak?

Sine Wave Terminology and Characteristics Peak RMS Average If Peak is 150V What Peak-to-Peak? 300V

Sine Wave Terminology and Characteristics Peak RMS Average If AVG is 125V What is RMS? What is Peak?

Sine Wave Terminology and Characteristics Peak RMS Average If AVG is 125V What is RMS? 139V What is Peak? 196V

Sine Wave Terminology and Characteristics Peak RMS Average If RMS is 125V What is Peak-to-Peak? What is avg? What is Peak?

Sine Wave Terminology and Characteristics Peak RMS Average If RMS is 125V What is Peak-to-Peak? 354V What is AVG? 113V What is Peak? 177V

Sine Wave Terminology and Characteristics RMS relates directly to an equivalent DC value:

Peak, RMS, DC (constant value) Sine Wave Terminology and Characteristics What is peak? What is peak to peak?

Peak, RMS, DC (constant value) Sine Wave Terminology and Characteristics What is peak? 339V What is peak to peak? 678V In the field, we ALMOST ALWAYS work with RMS values for AC circuits. Unless explicitly indicated otherwise, assume you are using RMS voltage values.

Sine Wave Terminology and Characteristics Phase: -In phase -Out of phase Waves are in phase when they cross the zero points (x-axis) at the same time and the peaks occur, with the same sign (positive or negative) at the same time.

Sine Wave Terminology and Characteristics Phase: -In phase -Out of phase If we think of a wave as having peaks and valleys with a zero-crossing between them, the phase of the wave is defined as the distance between the first zero-crossing and the point in space defined as the origin. - www.learner.org and have the same sign (i.e., positive ot negative) In phase or out of phase? How many degrees out of phase?

Sine Wave Terminology and Characteristics Don t forget, there are non-sinusoidal wave forms. Phase angle is only used for the sine wave because it is the only one which results from rotation generation.

Sine Wave Terminology and Characteristics Quiz 1 1. The minimum voltage is generated by rotating wire when the conductor is moving. a. Across the field at 90 degrees b. With the field at 0 degrees and 180 degrees c. Across the fields at 45 degrees d. Against the field at 180 degrees 2. For an AC circuit, one full cycle represents. a. 0 degrees b. 90 degrees c. 270 degrees d. 360 degrees 3. What is the Hz rating of an AC circuit if the frequency is 60 cycles per ½ second? 4. A circuit has a peak value of 310V, what is the average value?

Sine Wave Terminology and Characteristics Quiz 1 1. The minimum voltage is generated by rotating wire when the conductor is moving. a. Across the field at 90 degrees b. With the field at 0 degrees and 180 degrees c. Across the fields at 45 degrees d. Against the field at 180 degrees 2. For an AC circuit, one full cycle represents. a. 0 degrees b. 90 degrees c. 270 degrees d. 360 degrees 3. What is the Hz rating of an AC circuit if the frequency is 60 cycles per ½ second? 120Hz 4. A circuit has a peak value of 310V, what is the average value? 197.5V

Sine Wave Terminology and Characteristics Quiz 2 1. In sine wave terminology, the RMS value is a. 0.637 x peak b. 0.707 x peak c. 3.1416 x peak d. 2 x peak 2. If the time for one cycle is 0.01 second, the frequency is a. 0.01 Hz b. 0.1 Hz c. 10 Hz d. 100 Hz 3. Normal AC electricity in North America changes directions how many times per second? 4. Each change of direction is question 3 is known as a(n) 5. Normal AC electricity in North America cycles how many times per second? 6. What is the frequency of normal AC electricity in North America?

Sine Wave Terminology and Characteristics Quiz 2 1. In sine wave terminology, the RMS value is a. 0.637 x peak b. 0.707 x peak c. 3.1416 x peak d. 2 x peak 2. If the time for one cycle is 0.01 second, the frequency is a. 0.01 Hz b. 0.1 Hz c. 10 Hz d. 100 Hz 3. Normal AC electricity in North America changes directions how many times per second? 120 times or 120 alternations 4. Each change of direction in question 3 is known as a(n) alternation 5. Normal AC electricity in North America cycles how many times per second? 60 times per second or 60 Hz 6. What is the frequency of normal AC electricity in North America? 60 Hz

Sine Wave Terminology and Characteristics Quiz 3 1. The typical voltage values encountered in field work for a single phase AC circuit for receptacles is 120V. This values is a a. Peak value b. Peak-to-peak value c. Average value d. RMS value 2. If the phase angles for two sine waves are both 180 degrees, then the two waves. a. Have the same amplitude b. Are in phase c. Have the same peak values d. Are out of phase 3. Given a circuit has an RMS value of 277V, what is the peak value? 4. Given a circuit has an RMS value of 277V what is the peak-to-peak value? 5. Given a circuit has an RMS value of 277V what is the average value?

Sine Wave Terminology and Characteristics Quiz 3 1. The typical voltage values encountered in field work for a single phase AC circuit for receptacles is 120V. This values is a a. Peak value b. Peak-to-peak value c. Average value d. RMS value 2. If the phase angles for two sine waves are both 180 degrees, then the two waves. a. Have the same amplitude b. Are in phase c. Have the same peak values d. Are out of phase 3. Given a circuit has an RMS value of 277V, what is the peak value? 391V 4. Given a circuit has an RMS value of 277V what is the peak-to-peak value? 782V 5. Given a circuit has an RMS value of 277V what is the average value? 250V

Basic Load Types Resistance, Inductance, Capacitance What types of loads do these groups of symbols represent? 1.) 2.) 3.)

Basic Load Type Resistance, Inductance, Capacitance AC source of voltage: Sine wave in a circle Resistive load symbol: Saw tooth wave.

Basic Load Type Resistance, Inductance, Capacitance AC source of voltage: Sine wave in a circle Resistive load symbol: Saw tooth wave. In purely* resistive AC circuits, Ohm s Law applies just as if this were DC circuit. (*purely resistive means no other load type in series or parallel in the circuit). E = IR

Basic Load Type Resistance, Inductance, Capacitance AC source of voltage: Sine wave in a circle Resistive load symbol: Saw tooth wave. 4 Ohms What is the current in this circuit? In purely* resistive AC circuits, Ohm s Law applies just as if this were DC circuit. (*purely resistive means no other load type in series or parallel in the circuit). E = IR

Basic Load Type Resistance, Inductance, Capacitance AC source of voltage: Sine wave in a circle 30 Amps Resistive load symbol: Saw tooth wave. 4 Ohms In purely* resistive AC circuits, Ohm s Law applies just as if this were DC circuit. (*purely resistive means no other load type in series or parallel in the circuit). E = IR

Basic Load Type Resistance, Inductance, Capacitance AC source of voltage: Sine wave in a circle To find I T, we need to find R T first 4 Ohms 6 Ohms To find R T, we have to use a parallel resistors formula. E = IR

Basic Load Type Resistance, Inductance, Capacitance (Reciprocal formula) R T = 1 4 1 + 1 6 4 Ohms 6 Ohms R T = 4 x 6 (Product over sum) 4 + 6 E = IR

Basic Load Type Resistance, Inductance, Capacitance (Reciprocal formula) R T = 1 4 1 + 1 6 = 2.4 Ω 4 Ohms 6 Ohms R T = (Product over sum) 4 x 6 4 + 6 = 2.4 Ω E = IR

Basic Load Type Resistance, Inductance, Capacitance (Reciprocal formula) R T = 1 4 1 + 1 6 = 2.4 Ω 4 Ohms 6 Ohms R T = (Product over sum) 4 x 6 4 + 6 = 2.4 Ω Now use Ohm s Law. E = IR

Basic Load Type Resistance, Inductance, Capacitance What are the units?? I T = E R 120 V = = 50 A 2.4 Ω 4 Ohms 6 Ohms E = IR

Basic Load Type Resistance, Inductance, Capacitance In purely* resistive AC circuits, Ohm s Law applies just as if this were DC circuit. (*purely resistive means no other load type in series or parallel in the circuit). What are examples of resistive loads?

Basic Load Type Resistance, Inductance, Capacitance Capacitive load symbol:

Basic Load Type Resistance, Inductance, Capacitance Capacitor: A fundamental electrical element having two conducting surfaces separated by an insulating material and having the capacity to store charge on its plates. Capacitance: A measure of a capacitor s ability to store charge; measured in farads (F).

Basic Load Type Resistance, Inductance, Capacitance As the capacitor charges or discharges, a current flows through it which is restricted by the internal impedance of the capacitor. This internal impedance is commonly known as Capacitive Reactance and is given the symbol X C in Ohms. Unlike resistance which has a fixed value, for example, 100Ωs, 1kΩ, 10kΩ etc, (this is because resistance obeys Ohms Law), Capacitive Reactance varies with the applied frequency so any variation in supply frequency will have a big effect on the capacitors, capacitive reactance value. As the frequency applied to the capacitor increases, its effect is to decrease its reactance (measured in ohms). Likewise as the frequency across the capacitor decreases its reactance value increases. Notice frequency and capacitive resistance are INVERSELY related. Capacitance in farads 3.14 Frequency in HZ

Basic Load Type Resistance, Inductance, Capacitance Think of reactance as something that does the opposite of the main action it is a re-action and it resists the main action Hence reactance measured in ohms Capacitive Reactance Inductive Reactance Inductance measured In henrys. - Remember formulas with NFL and NFC. First make the jump that the symbol Π looks like a letter n. Now think of football the National Football Conference is a subset or subsidiary conference in the National Football League (put NFC in denominator) of the NFL.

Basic Load Type Resistance, Inductance, Capacitance Factors that affect capacitance: Area of the plates: More area, more capacitance. Distance between plates: Less distance, more capacitance. Dielectric Permittivity: More permittivity, more capacitance.

Basic Load Type Resistance, Inductance, Capacitance Factors that affect capacitance: INVERSELY RELATED!!! Area of the plates: More area, more capacitance. Distance between plates: Less distance, more capacitance. Dielectric Permittivity: More permittivity, more capacitance.

Basic Load Type Resistance, Inductance, Capacitance When capacitors are in parallel this has the effect of making one capacitor with a larger area. This means capacitors in parallel can be added together to determine total capacitance. To determine overall capacitance in series, the reciprocal formula must be used. Putting capacitors in series has the effect of making the dielectric thicker. All of this means capacitors are calculated the opposite of resistors.!ay Caramba!

Basic Load Type Resistance, Inductance, Capacitance Given two capacitors are in series and one capacitor is 10 μf and another is 20 μf, what is C T? 10 μf 20 μf

Basic Load Type Resistance, Inductance, Capacitance Given two capacitors are in series and one capacitor is 10 μf and another is 20 μf, what is C T? 1 10 μf R T = 1 10 + 1 20 20 μf Use reciprocal formula:

Basic Load Type Resistance, Inductance, Capacitance Given two capacitors are in series and one capacitor is 10 μf and another is 10 μf, what is C T? 1 10 μf R T = 1 10 + 1 20 = 6.67 μf 10 μf Use reciprocal formula: Kirchoff s Law applies to voltage. E = V 1 + V 2 + V 3. Across each capacitor in series, the voltage will drop. In this case, this means each of the two equal capacitors has one-half the applied voltage.

Basic Load Type Resistance, Inductance, Capacitance Each of five equal capacitors in series has the applied voltage? a. 5% b. 5 times c. 50% d. 1/5

Basic Load Type Resistance, Inductance, Capacitance Given two capacitors are in parallel and one capacitor is 10 μf and another is 20 μf, what is C T?

Basic Load Type Resistance, Inductance, Capacitance Given two capacitors are in parallel and one capacitor is 10 μf and another is 20 μf, what is C T? 10μF + 20 μf =30 μf

Basic Load Type Resistance, Inductance, Capacitance Examples of Capacitive loads: - capacitor banks (used to improve power factor) - electronic power supplies

Basic Load Type Resistance, Inductance, Capacitance AC source of voltage: Sine wave in a circle Inductor load symbol: Inductor: A fundamental element of electrical systems constructed of numerous turns of wire around a core. Inductance: a measure of the ability of a coil to oppose any change in current through the coil and to store energy in the form of a magnetic field in the region surrounding the coil. Inductance is the result of the expanding and collapsing field caused by the changing current no current change, no inductance.

Basic Load Type Resistance, Inductance, Capacitance

Basic Load Type Resistance, Inductance, Capacitance Inductive reactance. This is the counter EMF (CEMF). This is the same as saying the counter voltage, or force against the original force. More inductance, more inductive reactance. Higher Frequency, more inductive reactance. How does this compare to capacitive reactance:

Basic Load Type Resistance, Inductance, Capacitance Examples of Inductive Loads are:

Basic Load Type Resistance, Inductance, Capacitance Examples of Inductive Loads are: Motors xfmr solenoid Relays and Contactors

Basic Load Type ELI the ICE man We have studied three types of loads on an electrical circuit. These loads are?

Basic Load Type ELI the ICE man We have studied three types of loads on an electrical circuit. These loads are? 1. Resistive 2. Capacitive 3. Inductive

Basic Load Type ELI the ICE man 1. Resistive 2. Capacitive 3. Inductive

Basic Load Type ELI the ICE man ELI the ICE man is a mnemonic that helps to remember the PHASE RELATIONSHIP Between CURRENT and VOLTAGE in inductive and capacitive circuits.

Basic Load Type ELI the ICE man A mnemonic is: a device such as a pattern of letters, ideas, or associations that assists in remembering something.

INDUCTIVE AC circuit CAPACITIVE AC circuit Alternating Current Study Guide Basic Load Type ELI the ICE man

Basic Load Type ELI the ICE man ELI the ICE man is a mnemonic that aids in remembering the phase relationship between the voltage and current in an AC circuit. E = voltage L = Inductance I = Current (electromotive force, measured in volts) (L is used due to Heinrich Lenz, measured in henrys) (intensité de courant French, measured in amps) C= Capacitance (F is used indicating farads, measure in farads.

Basic Load Type ELI the ICE man In an inductive circuit ELI the ICE man Voltage leads Current E = voltage L = Inductance I = Current (electromotive force, measured in volts) (L is used due to Heinrich Lenz, measured in henrys) (intensité de courant French, measured in amps) C= Capacitance (F is used indicating farads, measure in farads.

Basic Load Type ELI the ICE man In an capacitive circuit ELI the ICE man Current leads Voltage E = voltage L = Inductance I = Current (electromotive force, measured in volts) (L is used due to Heinrich Lenz, measured in henrys) (intensité de courant French, measured in amps) C= Capacitance (F is used indicating farads, measure in farads.

INDUCTIVE AC circuit CAPACITIVE AC circuit Alternating Current Study Guide Basic Load Type ELI the ICE man

RESISTIVE AC circuit Alternating Current Study Guide Basic Load Type ELI the ICE man

RESISTIVE AC circuit Alternating Current Study Guide Basic Load Type ELI the ICE man So ELI the ICE man has no application to RESISTIVE circuits because the relationship between voltage and current is IN PHASE.

Basic Load Type ELI the ICE man Finally, remember: An inductor opposes changes is current. A capacitor opposes changes in voltage. ELI the ICE man help you to remember this, too! The current follows the voltage because the INDUCTOR opposes a change in current. The voltage follows the current because the CAPACITOR opposes a change in voltage.

QUIZ 1 Three Types of Loads 1. What does the E the L and the I stand for in ELI the ICE man? 2. What are the three types of circuit loads discussed in this module 3. Each of six equal capacitors in series has the applied voltage? a. 6.67 times b. 6 times c. 1/6 d. 0.6 4. Write the formula for capacitive reactance: 5. What is the numeric value of pi (Π)?

QUIZ 1 Three Types of Loads 1. What does the E the L and the I stand for in ELI the ICE man? E = voltage, I = current, L = inductive circuit 2. What are the three types of circuit loads discussed in this module Resistive, Capacitive, Inductive 3. Each of six equal capacitors in series has the applied voltage? a. 6.67 times b. 6 times c. 1/6 d. 0.6 4. Write the formula for capacitive reactance: 5. What is the numeric value of pi (Π)? 3.14 or 3.1416

QUIZ 2 Three Types of Loads 1. What does the I the C and the E stand for in ELI the ICE man? 2. Write the formula for inductive reactance. 3. Based on the formula for inductive reactance, what increases inductive reactance. 4. Current leads the voltage in what type of circuit? 5. Current and voltage are in phase in what type of circuit?

QUIZ 2 Three Types of Loads 1. What does the I the C and the E stand for in ELI the ICE man? I = current, C = capacitive circuit, E = voltage 2. Write the formula for inductive reactance. 3. Based on the formula for inductive reactance, what increases inductive reactance. Frequency (f) and inductance (L) 4. Current leads the voltage in what type of circuit? Capacitive.ELI the ICE man 5. Current and voltage are in phase in what type of circuit? Resistive

QUIZ 3 Three Types of Loads 1. In a capacitive circuit the current leads the voltage? True/False 2. In a inductive circuit, the voltage leads the current? True/False 3. Based on the formula for inductive reactance, what increases inductive reactance. 4. If the area of capacitor plates are increased, the capacitance. Increases/Decreases 5. ELI the ICE man helps to remember the phase relationships between current and voltage in resistive circuits and inductive circuits. True/False

QUIZ 3 Three Types of Loads 1. In a capacitive circuit the current leads the voltage? True/False True ICE 2. In a inductive circuit, the voltage leads the current? True/False True ELI 3. Based on the formula for inductive reactance, what increases inductive reactance. Frequency and inductance 4. If the area of capacitor plates are increased, the capacitance. Increases/Decreases Increases 5. ELI the ICE man helps to remember the phase relationships between current and voltage in resistive circuits and inductive circuits. True/False between current and voltage in an inductive circuit and a capacitive circuit.

QUIZ 4 Three Types of Loads 1. Write Ohm s Law 2. Given: An AC circuit containing resistance only. What is the voltage if the resistance is 4 ohms and the current is 60 amps? 3. Given: An AC circuit containing resistance only. What is the current flow if the resistance is 8 ohms and the voltage is 120 volts? 4. If the distance between capacitor plates is increased, the capacitance. Increases/Decreases

QUIZ 4 Three Types of Loads 1. Write Ohm s Law E = IR 2. Given: An AC circuit containing resistance only. What is the voltage if the resistance is 4 ohms and the current is 60 amps? E = 4 x 60 = 240V 3. Given: An AC circuit containing resistance only. What is the current flow if the resistance is 8 ohms and the voltage is 120 volts? E/R = 120/8 = 15A 4. If the distance between capacitor plates is increased, the capacitance. Increases/Decreases

QUIZ 5 Three Types of Loads 1. Write the formula for capacitive reactance. 2. Based on the formula for capacitive reactance, what factors will increase capacitive reactance? 3. Find C T for two capacitors in parallel. Capacitor One = 4 μf and Capacitor Two = 4 μf. 4. Find C T for two capacitors in series. Capacitor One = 4 μf and Capacitor Two = 4 μf.

QUIZ 5 Three Types of Loads 1. Write the formula for capacitive reactance. 2. Based on the formula for capacitive reactance, what factors will increase capacitive reactance? Decrease frequency, decrease capacitance 3. Find C T for two capacitors in parallel. Capacitor One = 4 μf and Capacitor Two = 4 μf. 4. Find C T for two capacitors in series. Capacitor One = 4 μf and Capacitor Two = 4 μf. 4 μf + 4 μf = 8 μf Product Over Sum: (4x4) / (4 + 4) = 16 / 8 = 2 μf Capacitors of Equal Value: C/N = 4 / 2 = 2 μf Reciprocal Method: = 1 / ((1/4) + (1/4)) = 1 / (1/2) = 2 μf

Basic Load Type Power Triangle and Power Factor (True) The Power Triangle

Basic Load Type Power Triangle and Power Factor (True) The Power Triangle This is a vector diagram. The length of the vectors represent the magnitude.

Basic Load Type Power Triangle and Power Factor Here is how I remember the triangle. It s stupid but it helps me remember. Sometimes a train has to Ascend a mountain. Ascend helps to remember Apparent Power. (True) Trains prefer to travel on flat tracks. (The t-r in trains help to remember t-r in True Power. Flat tracks helps to remember level line of triangle A train can never Rise straight up a mountain. Rise helps to remember Reactive Power.

Basic Load Type Power Triangle and Power Factor POWER FACTOR (True) 1. The power company makes VA 3. This is what we use after the reactance affects the supply. 2. Because of all the inductive loads and capacitive loads, there is some level of reactance causing a loss of efficiency

Basic Load Type Power Triangle and Power Factor POWER FACTOR (True) 1. The power company makes VA 3. This is what we use after the reactance affects the supply. PF = P True P Apparent 2. Because of all the inductive loads and capacitive loads, there is some level of reactance causing a loss of efficiency creating all of these electro-magnetic fields is necessary to perform work, but the magnetic fields don t actually do work.

Basic Load Type Power Triangle and Power Factor POWER FACTOR PF = P T P A This is an efficiency ratio. The value will e between 0 and 1. Of course 1 is perfect efficiency. Facilities try to target 0.9 or better. As the customer you want good efficiency because you are paying for P A and your getting P T as your output. Also the power company is going to start charging you a premium to clean up all the reactive power effects. Low PF is a double whammy!

QUIZ 1 Power Triangle and Power Factor 1. Draw the Power Triangle, showing what each of the three sides represents. 2. Reactive Power is greater than Apparent Power. True/False 3. True, or Real Power, is greater than Apparent Power. True/False 4. Power = I 2 R is the formula for a. True, or Real Power. b. Reactive Power. c. Apparent Power. d. Super Power

QUIZ 1 Power Triangle and Power Factor 1. Draw the Power Triangle, showing what each of the three sides represents. 2. Reactive Power is greater than Apparent Power. True/False Apparent is the hypotenuse, it will always be biggest 3. True, or Real Power, is greater than Apparent Power. True/False Apparent is the hypotenuse, it will always be biggest (True) 4. Power = I 2 R is the formula for a. True, or Real Power. b. Reactive Power. c. Apparent Power. d. Super Power

QUIZ 2 Power Triangle and Power Factor 1. What does PF stand for? 2. The ratio of Power to Apparent Power is called Power Factor? 3. Apparent Power is greater than Real, or True, Power True/False 4. Power = IE is the formula for a. True, or Real Power. b. Reactive Power. c. Apparent Power. d. Super Power

QUIZ 2 Power Triangle and Power Factor 1. What does PF stand for? POWER FACTOR REAL/TRUE 2. The ratio of Power to Apparent Power is called Power Factor? 3. Apparent Power is greater than Real, or True, Power True/False 4. Power = IE is the formula for a. True, or Real Power. b. Reactive Power. c. Apparent Power. d. Super Power

Transformers Let s think about what a transformer is. In your NCCER text a transformer is defined as: - A device that transforms electrical energy from one circuit to another by electromagnetic induction. The energy is transferred WITHOUT a change in frequency. If the primary circuit is 60Hz the secondary circuit is 60Hz. The Frequency is constant. However, the CURRENT and VOLTAGE do usually change when the energy is transferred in the transformer. In fact, most of the time when we install a transformer, it is primarily to change high voltage to lower voltage for things like receptacle panels.

Transformers Look at this basic transformer figure. Let s assume the first circuit is 480V (primary winding) and the other circuit (the secondary winding) will be a lower voltage, say 120V or 240V or 208V. We typically install a transformer because at some source we have a voltage too high for the load, so we have to transfer this electrical energy to a separate circuit (via electromagnetic induction (the transformer s job) to another, usually lower voltage, circuit.

Transformers Lower Voltage 208V Higher current 208A High voltage 480V Lower current 90A STEP-DOWN xfmr Typically installed for our field work

Transformers Lower Voltage 208V Higher current 208A High voltage 480V Lower current 90A STEP-DOWN xfmr Typically installed for our field work I P E POWER IS CONSTANT. The power provided by the primary circuit is equal to the power provided by the secondary circuit. Power = Volts x Amps 75,000 VA on primary side is equal to 75,000 VA on secondary side. This is a 75kVA transformer.

Transformers Secondary winding will always go to the electrical LOAD. Primary winding will always be from the electrical SOURCE.

Transformers - VOLTAGE RELATIONSHIP Not every transformer is a STEP-DOWN. You can have a STEP-UP transformer. High voltage at primary STEPPED DOWN to lower voltage at secondary. Low voltage at primary STEPPED UP to higher voltage at secondary.` Don t assume you can wire a transformer backwards to use lower voltage primary to get higher voltage secondary. The transformer has to be a STEP-UP or a regular transformer has to be REVERSE FEED CAPABLE

Voltage Alternating Current Study Guide Transformers PHASE RELATIONSHIP Some Transformers have the primary and secondary voltage IN PHASE. These are called LIKE-WOUND transformers 480V 208V Time

Voltage Alternating Current Study Guide Transformers PHASE RELATIONSHIP Some Transformers have the primary and secondary voltage 180 degrees out of phase. These are called UNLIKE-WOUND transformers 480V 208V Time

Transformers Turns and Turns Ratio The turns ratio affects the change in voltage from the primary side to the secondary side. In the turns ratio, the primary turns are always listed first, than the secondary turns. So using the figure below the turns ratio would be 10:5 (or reduce to 2:1) 5 Turns 10 Turns

Transformers - Turns and Turns Ratio The voltage change is directly proportional to this turns ratio. So in the figure below, with a 2:1 turns ratio, if the primary voltage was 120V what would the secondary voltage be? 5 Turns 10 Turns

Transformers Turns and Turns Ratio The voltage change is directly proportional to this turns ratio. So in the figure below, with a 2:1 turns ratio, if the primary voltage was 120V what would the secondary voltage be? 60V 5 Turns 10 Turns

Transformers Special Types Isolation Transformer Autotransformer Current Transformer

Transformers Special Types Isolation Transformer Autotransformer Current Transformers (one xfmr on each phase)

Transformers Special Types Current Transformer = CT

Transformers Special Types CTs which will feed a ammeter. CT Cabinet

Transformers Special Types More typical mounting of CTs for service conductors note that the CTs are hard-mounted and not floating. (sorry, best picture we could find for now.)

QUIZ 1 1. Electricity from the power source connects at the windings. Electricity from the windings goes out to the load. 2. A is a device that transforms electrical energy from one circuit to another by electromagnetic induction. 3. Frequency is the (same/different) at the primary and secondary windings of a transformer. 4. Transformers work via e i (aka transformer action).

QUIZ 1 primary 1. Electricity from the power source connects at the windings. secondary Electricity from the windings goes out to the load. transformer 2. A is a device that transforms electrical energy from one circuit to another by electromagnetic induction. 3. Frequency is the (same/different) at the primary and secondary windings of a transformer. 4. Transformers work via electro-magnetic induction (aka transformer action).

QUIZ 2 1. A transformer has a 4:1 turns ratio. The secondary voltage is 75V. What is the primary voltage. 2. In transformers turn ratios, the is always the first number in the ratio. 3. A transformer has a 3:1 turns ratio. The primary voltage is 75V. What is the secondary voltage. 4. It is not recommended to open a CT s secondary when the primary is under load - true/false

QUIZ 2 1. A transformer has a 4:1 turns ratio. The secondary voltage is 75V. What is the primary voltage. 300V primary 2. In transformers turn ratios, the is always the first number in the ratio. 3. A transformer has a 3:1 turns ratio. The primary voltage is 75V. What is the secondary voltage. 25V 4. It is not recommended to open a CT s secondary when the primary is under load - true/false

QUIZ 3 1. We typically install a step- transformer in the field to change the primary voltage of 480V down to a 208/120V panel. 2. A facility has a 208V service. A 480V HVAC unit has been installed. To supply the new unit with 480V you will need either a step- transformer or a properly sized reverse capable xfmr. 3. A given transformer has the following phase relationship: when the primary is +480V the secondary is +240. Based on this phase relationship, what type of transformer is this: - wound. 4. A current transformer is also known as a (two letters).

QUIZ 3 1. We typically install a step- down transformer in the field to change the primary voltage of 480V down to a 208/120V panel. 2. A facility has a 208V service. A 480V HVAC unit has been installed. To supply the new unit with 480V you will need either a step- up transformer or a properly sized reverse feed capable xfmr. 3. A given transformer has the following phase relationship: when the primary is +480V the secondary is +240. Based on this phase relationship, what type of transformer is this: like - wound. CT 4. A current transformer is also known as a (two letters).

QUIZ 4 1. There are three phase conductors for a service for a given facility. The service is active and loaded. What would happen if you were to remove the secondary wires from one of the CTs while it was under load? A dangerously high would likely occur.

QUIZ 5 1. Based on figure below, these voltage curves indicate a step-up or step-down transformer? 2. Based on the figure below, these voltage curves indicate a like-wound or unlike-wound transformer?

QUIZ 5 1. Based on figure below, these voltage curves indicate a step-up or step-down transformer? Step-up (aka Buck and Boost 2. Based on the figure below, these voltage curves indicate a like-wound or unlike-wound transformer? unlike wound