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Experiment 2: Simulation
Introduction to Matlab/Simulink and Transformer Tests Using Simulink
Modified date: 01-05-
Transformer Tests Using Simulink
Objectives:
The main objective is to obtain transformer equivalent circuit parameters by simulating three transformer tests.
This part of the lab consists of three different simulations:
- Open Circuit Test
- Short Circuit Test
- Load Test
Simulations are designed to follow the actual hardware experiments as closely as possible. That will give you a chance to compare the simulation results to those of the actual experiment. For the tests, we will use the Matlab Power System Blockset that provides models of the main elements of power systems such loads, transformers, etc. Simulink diagrams for each test will be provided during the experiment. The single-phase transformer used in these simulations has the following nameplate information and the equivalent circuit is given in Fig. 1.
Nameplate Information: Rated Power: 2500 VA Rated Voltage: 120/120 V Rated Frequency: 60 Hz
R p
Xp
R s
Xs
V s
I s
V p R^ c jXm
I p
ideal
transformer
Figure 1: Equivalent circuit of a transformer
No Load Test:
This test will provide you with core losses of the transformer. Using simulation results you will able to determine the magnetization resistance and reactance of the transformer (Rc and Xm). The Simulink diagram is depicted in Figure 2. Please open the Simulink diagram called xformer_noload and spend some time to understand it. As shown in Figure 2, we have a single-phase transformer that is connected to an RLC load. An AC source is connected to the primary side of the transformer. We use several measurement blocks of the Power System Blockset to measure real and reactive power of the primary, voltages and currents (including phase angles) of the primary and secondary. The simulations parameters are already set up for you. In order to simulate the no load situation under various voltage level, a very small amount of real and reactive power loads are chosen (double-click on the series RLC load to see the values). Please follow the steps below:
Experiment 2: Simulation
Introduction to Matlab/Simulink and Transformer Tests Using Simulink
Modified date: 01-05-
- Set the AC source peak voltage value to 0 V. To do that, double-click the AC source and set the peak amplitude (V) to 0. Do not change anything else and save the changes.
- Run the simulation (Simulation/Start).
- Double-click on the powergui (blue box on the left) to see the RMS values of voltages and currents: click Steady-State Voltages and Currents , then choose RMS values. in the dialog box for Units, record measurements in Table 1: primary voltage ( Primary Voltage ) , scondary voltage ( Secondary Voltage ), primary current( Current Measurement ), secondary current ( Current Measurement 1 ).
- Type real_reactive_power(length(real_reactive_power),:) in the MATLAB workspace (and hit “Enter”) to obtain input real and reactive powers. It will give you the values of P and Q. The first component of the row is the input real power (P in watts) and the second component is the input reactive power (Q in VARS).
- Record your data in a table format shown in Table 1.
- Repeat the steps from 1 to 5 for the voltage values: 30, 60, 90, 120, 150, and 170 V.
- Record your data in the same table.
- Note that the data at 170 V corresponds to the rated rms voltage (120 V). Why is this so? The rms values of the primary voltage and current, and the input real power will be used to compute the magnetization resistance and reactance of the transformer (R (^) c and X (^) m).
- For your lab report
- Compute and record values for Rc and X (^) m
- Provide the table containing all the data
- Plot current vs. voltage for both the primary and secondary side
- Plot the input real power vs. input voltage (primary voltage)
- Compare your results with those obtained from the actual hardware experiments.
- Information on powergui: Please refer to the list to obtain the measurements in Table 1 from the list in powergui: **1. Vp =Primary Voltage
- Ip = Current Measurement
- Vs = Secondary Voltage
- Is = Current Measurement**
Table 1: Example Table for No Load Test
Vac peak Value (V)
RMS
Primary Voltage, Vp (V)
RMS
Primary Current Ip (A)
Ip Phase Angle (degrees)
RMS
Secondar y Voltage Vs (V)
RMS
Secondar y Current Is (A)
Is Phase Angle (degrees)
Input Real Power P (W)
Input Reactive Power (VAR)
0 30 60 90 120 150 170
Experiment 2: Simulation
Introduction to Matlab/Simulink and Transformer Tests Using Simulink
Modified date: 01-05-
- Type real_reactive_power(length(real_reactive_power),:) in the MATLAB workspace (and hit “Enter”) to obtain input real and reactive powers. It will give you the values of P and Q. The first component of the row is the input real power (P in watts) and the second component is the input reactive power (Q in VARS).
- Record your date in a table format shown in Table 2.
- Repeat the steps from 1 to 5 for the voltage values: 5, 10, 15, 17, 20 V.
- Record your data in the table below.
- Note that the data at 20 V approximately corresponds to the rated rms current (20.83A V). The rms values of the primary voltage and current, and the input real power will be used to compute the equivalent winding resistance and reactance of windings, which are referred to the primary side (Req and Zeq ).
- For your lab report
- Compute and record Req and Zeq.
- Provide the table containing all the data
- Plot current vs. voltage for both primary and secondary
- Plot the input real power vs. input voltage (primary voltage)
- Compare you results with those of the actual hardware experiment.
Table 2: Example table for Short Circuit Test
Vac peak Value (V)
RMS
Primary voltage, Vp (V)
RMS
Primary Current Ip (A)
Ip phase angle (degrees)
RMS
Secondar y Voltage Vs (V)
RMS
Secondar y Current Is (A)
Is phase angle (degrees)
Input real power P (W)
Input reactive power (VAR)
0 5 10 15 17 20
Experiment 2: Simulation
Introduction to Matlab/Simulink and Transformer Tests Using Simulink
Modified date: 01-05-
Figure 3: The Simulink diagram for short circuit test
Load Test:
The load test is designed to study the effects of the three different types of loads on the voltage regulation and efficiency of the transformer. Fig. 4 shows the Simulink diagram for the load test. Observe that a series RLC load is connected to the secondary side. Double-click in the series RLC load in the Simulink diagram. A dialog box shown in Fig. 5 will pop up. This dialog box allows you to specify the real, inductive reactive and capacitive reactive power components of the load. We will simulate the following load types:
1. Load 1-resistive load: Nominal voltage = 120 V, Nominal frequency = 60 Hz, Active power P (W) = 2500, Inductive reactive power QL = 0 and Capacitive reactive power Qc = 0. 2. Load 2-Inductive load: Nominal voltage = 120 V, Nominal frequency = 60 Hz, Active power P (W) =2500 Inductive reactive power QL = 1090 Var and Capacitive reactive power Qc = 0. 3. Load 3-Capacitive load: Nominal voltage = 120 V, Nominal frequency = 60 Hz, Active power P (W) = 2500, Inductive reactive power QL = 0 and Capacitive reactive power Qc = 1500 Var.
Experiment 2: Simulation
Introduction to Matlab/Simulink and Transformer Tests Using Simulink
Modified date: 01-05-
Figure 4: The Simulink diagram for the load test
Figure 5: The RLC load dialog box
