Name: Student ID: MS2203 Electric Motors and Drivers Module 1 – Introduction to Electric Power Measurement A. Notice You will conduct an experiment with high voltage, and please be careful! Please check the voltage and current using a Multimeter before measuring it by Oscilloscope. B. Learning Objectives Students understand the function of a fuse and a current breaker. Students are able to use a test pen to check the ‘live’ terminal. Students are able to measure resistance. Students are able to measure electric current and electric voltage using a Multimeter. Students are able to use Oscilloscope to measure signal period, peak, peak-to-peak, and RMS (Root Mean Square) value. C. Theory 1. There is two main safety device which will be introduced: fuse and current breaker. Both fuse and current breaker will cut off when electrical current flows into the circuit exceed its maximum current limit. The fuse is a non-reusable device, when an excessive current flows through the circuit, it will be burned and can’t be used again. A circuit breaker, contrary to fuse, is a reusable device. It works just like a switch, when an excessive current flows into the circuit, the current breaker will be automatically turned off. After several minutes, it can be turned on again. Both fuse and current breaker are put in the ‘live’ line. To check whether the terminal is a ‘live’ terminal or not, we will use a test pen. A small light inside the test pen will be turned on when the test pen is connected to the ‘live’ terminal. Figure 1 shows an illustration of how to conduct the test pen experiment. 1 Figure 1. Schematic of Test Pen experiment 2. A multimeter is employed to measure voltage, current, resistance, and capacitance. Figure 2 shows that Multimeter consists of three major parts, such as: a) Selector button: to determine the types of measurement b) The positive and negative terminal c) Display: to show the measurement result Multimeter as Voltmeter Selector button Multimeter as Amperemeter Figure 2. Multimeter Multimeter should be installed in series with the load when it is applied to measure current. Meanwhile, the Multimeter is installed parallel with the load when it is applied to measure electrical voltage. 3. Signal Generator is used for generating electric signal. Figure 3 shows that there are four main buttons in Signal Generator: a) Signal type button: to choose the signal types b) Frequency button: to adjust the signal frequency c) Amplitude button: to adjust the signal amplitude d) Offset button: to set the offset value 2 Frequency button Signal type Amplitude button button Offset button Display Figure 3. Signal Generator Figure 4 shows the definition of offset, amplitude, and period of a sinusoidal signal. Offset is the distance between the average of sinusoidal signal and zero reference, the amplitude is the maximum voltage value from the average value, and period is a time between two successive peaks. The peak value is the farthest point from zero reference, or it can be calculated by amplitude plus offset. Meanwhile, the value of peak-to-peak is two times Voltage (Volt) amplitude. Time (sec) Figure 4. The definition of offset, amplitude, and period in sinusoidal signal 4. An oscilloscope is a device to observe electric signals (voltage vs time). In Oscilloscope, there are two cursors that can be used to determine the signal properties, such as peak-topeak and period. Normally, a vertical cursor is used to measure the signal period, meanwhile a horizontal cursor is used to measure peak-to-peak value. The following link can help students who want to learn how to use the cursor in Oscilloscope. Link: https://www.youtube.com/watch?v=xUZNJd4Aq00 (Keyword: cursor use on Oscilloscope). 3 D. Student Worksheet 1. Grid Voltage Measurement Please measure the RMS and frequency of grid voltage. Based on the measurement result, calculate the peak value of grid voltage and the grid voltage period. VRMS = ____________ Volt Vp = ____________ Volt 𝑓 = ________________ Hz T = _____________ s Does the measurement results are the same as the theoretical value? If not, why does it happen? Answer: _____________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ 2. Test Pen Find the ‘Live’ terminal by using a test pen! Explain how it works! Answer: ________________________________________________________________________________________ ___________________________________________________________________________________________________ ___________________________________________________________________________________________________ ___________________________________________________________________________________________________ Another method to find the ‘live’ terminal is by letting a small controlled current flows through your hand, as shown in the figure below. Live or Neutral terminal Figure 5. ‘Live’ or ‘Neutral’ terminal testing 4 What is the value of resistance used in this experiment? __________________________________ How many amperes pass through your hand? ______________________________________________ Explain how it works! Is it safe for us? Answer: ________________________________________________________________________________________ ___________________________________________________________________________________________________ ___________________________________________________________________________________________________ ___________________________________________________________________________________________________ 3. Fuse Make the electric circuit as shown in the following figure. Switch Load Fuse Figure 6. Fuse testing circuit Load (W) 100 Current (A) What does happen to the fuse and load? Fuse 0.1 A Fuse 0.4 A Fuse 0.75 A 200 300 Provide your analysis related to the measurement data! Answer: _____________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ 4. Current Breaker Make the electric circuit as shown in the figure below. 5 Switch Load Current Breaker Figure 7. Current Breaker testing circuit Load = 100 W, what happens? _____________________________________________________________________ Load = 200 W, what happens? _____________________________________________________________________ Load = 300 W, what happens? _____________________________________________________________________ Provide your analysis related to the measurement data! Answer: _____________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ ________________________________________________________________________________________________________ 5. Multimeter Resistance measurement Calculate the resistance of R1 and R2 (R1 > R2) using Multimeter. Calculate the error (%) towards theoretical value. R1 = , eror (%) = R2 = , eror (%) = What caused the error? _______________________________________________________________________________________________ _______________________________________________________________________________________________ Understanding the effect of internal resistance of Amperemeter Make the electric circuit as it is shown in Figure 8, then perform voltage and current measurement. Firstly, voltage is measured without Amperemeter is installed on the 6 circuit. After that, Amperemeter is installed on the circuit, is there any difference between both results? Figure 8. Current and voltage measurement at resistor V1 = ___________ Volt V2 = ___________ Volt (without Amperemeter) i (current) = ___________ A V2* = ___________ Volt (with Amperemeter) Calculate the internal resistance value of Amperemeter! Give your analysis! 6. Oscilloscope Voltage measurement The instructor will operate a signal generator to create a sinusoidal signal, rectangle signal, or triangle signal. For each signal, determine the type of signal, frequency or period, offset, amplitude, peak, and peak-to-peak value. Answer: 7
