AC source and load modeling in Simulink - Step-by-Step Execution

Concept Flow - AC source and load modeling

Define AC Source Parameters

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Generate AC Voltage Signal

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Connect Load Model

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Calculate Current and Power

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Analyze Output Waveforms

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End

This flow shows how an AC source is defined, connected to a load, and how current and power are calculated and analyzed.

Execution Sample

Simulink

ac_voltage = Vm * sin(2 * pi * f * t + phase)
current = ac_voltage / load_impedance
power = ac_voltage * current
plot(t, ac_voltage, t, current)

This code models an AC voltage source, calculates current through a load, computes power, and plots voltage and current over time.

Execution Table

Step	Time (t)	AC Voltage (V)	Load Impedance (Ohm)	Current (A)	Power (W)
1	0	0.0	10	0.0	0.0
2	0.001	6.28	10	0.628	3.94
3	0.002	12.35	10	1.235	15.25
4	0.003	17.32	10	1.732	30.0
5	0.004	20.0	10	2.0	40.0
6	0.005	20.0	10	2.0	40.0
7	0.006	17.32	10	1.732	30.0
8	0.007	12.35	10	1.235	15.25
9	0.008	6.28	10	0.628	3.94
10	0.009	0.0	10	0.0	0.0
11	0.01	-6.28	10	-0.628	3.94
12	0.011	-12.35	10	-1.235	15.25
13	0.012	-17.32	10	-1.732	30.0
14	0.013	-20.0	10	-2.0	40.0
15	0.014	-20.0	10	-2.0	40.0
16	0.015	-17.32	10	-1.732	30.0
17	0.016	-12.35	10	-1.235	15.25
18	0.017	-6.28	10	-0.628	3.94
19	0.018	0.0	10	0.0	0.0
20	0.019	6.28	10	0.628	3.94
Exit	0.02	0.0	10	0.0	0.0

💡 Simulation time reached 0.02 seconds, completing one full AC cycle.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	After 6	After 7	After 8	After 9	After 10	Final
ac_voltage (V)	0.0	6.28	12.35	17.32	20.0	20.0	17.32	12.35	6.28	0.0	0.0	0.0
current (A)	0.0	0.628	1.235	1.732	2.0	2.0	1.732	1.235	0.628	0.0	0.0	0.0
power (W)	0.0	3.94	15.25	30.0	40.0	40.0	30.0	15.25	3.94	0.0	0.0	0.0

Key Moments - 2 Insights

Why does the current have the same shape as the voltage but scaled down?

Because current is voltage divided by load impedance (Ohm's law), so it follows the voltage waveform shape but with smaller amplitude as shown in execution_table rows 2-10.

Why is power always positive even when voltage and current are negative?

Power is voltage times current; negative times negative gives positive power, indicating energy flow direction, as seen in execution_table rows 11-18.

Visual Quiz - 3 Questions

Look at the execution table at step 5, what is the current value?

A 2.0 A

B 1.732 A

C 0.628 A

D 0.0 A

💡 Hint

Check the 'Current (A)' column at step 5 in the execution_table.

At which step does the AC voltage first become negative?

A Step 10

B Step 11

C Step 9

D Step 12

💡 Hint

Look at the 'AC Voltage (V)' column in execution_table rows 10-12.

If the load impedance doubles, how does the current at step 5 change?

A It doubles

B It stays the same

C It halves

D It becomes zero

💡 Hint

Current = Voltage / Load Impedance; see variable_tracker for current changes.

Concept Snapshot

AC Source and Load Modeling:
- AC voltage: V = Vm * sin(2πft + phase)
- Current: I = V / Load Impedance
- Power: P = V * I
- Load affects current amplitude
- Power positive when voltage and current signs match

Full Transcript

This visual execution traces AC source and load modeling in Simulink. We start by defining AC source parameters, generating the voltage waveform, connecting a load, calculating current and power, and analyzing waveforms. The execution table shows voltage, current, and power values at each time step over one AC cycle. Current follows voltage shape scaled by load impedance. Power remains positive even when voltage and current are negative due to multiplication of two negatives. Key moments clarify why current waveform matches voltage shape and why power is always positive. The quiz tests understanding of current values, voltage sign changes, and effect of load impedance on current. The snapshot summarizes formulas and key points for AC source and load modeling.