B.
EXPERIMENT
Lab procedure:
Supply 60V DC of correct polarity to the inverter through a load box. Also, supply 120 V AC to the
inverter. Prepare to measure the input DC voltage and DC current. Note, the reset button on the inverter
must be pressed each time the inverter is energized.
a) Voltage waveforms:
With no signal input to the inverter and an open-circuit on the output (infinite load resistance) observe
and capture the FET gate voltages A and A’ on CH1 and CH2 of the oscilloscope. Also observe and
record the FFT of voltage A (be sure to look at frequencies out to at least 25kHz). Also, observe and
capture the voltages ( and ’ – these are the outputs of the inverter before the filter) and observe
and capture the difference between these voltages. Connect the two voltages ( and ’) to CH1 and
CH2 and use the MATH function to display the difference.
Repeat with a 0.2 V, 60 Hz, sinusoidal signal input voltage connected to the BNC input of the inverter.
b) No-load response:
Observe the filtered output of the inverter by connecting the output terminals to CH1 and CH2 and
using the MATH function to display the difference. Do not ground either output terminal. With an
open-circuit on the output of the inverter connect a sinusoidal 60 Hz input voltage so that the output
voltage is approximately 40 V peak to peak. Using DMM’s measure the signal input voltage and
output voltage at this frequency. Observe and capture the FFT of the filtered output under this no-load
configuration.
c) Efficiency:
Set the load resistance to 100 Ohms. At a frequency of 60 Hz, adjust the BNC input signal voltage so
that the output voltage varies between 10 and 40 V peak to peak in 5 V steps. Measure the input DC
voltage, current and the AC output voltage (rms). Capture one FFT of the filtered output.
Repeat with a 50 Ohm load.
Lab report:
a) Present and comment on the waveshapes observed at A and A’,  and ’ and at the output of the
inverter before the filter. Also comment on the FFT of the waveform at A.
b) Make a table for the measurements with both the 100 Ohm and 50 Ohm loads that includes
measured DC voltage and DC current, calculated DC input power, measured AC output voltage,
calculated output power and calculated efficiency.
Plot efficiency versus output voltage for each load. Comment on the efficiency of the inverter.