STATIC POWER INVERTERS



STATIC POWER INVERTERS

A. PREPARATION

1. Introduction

2. Variable Speed AC Drive

3. High Efficiency DC Supplies

4. Induction Heating

5. Conversion of DC Power to AC Power at the Terminus of a High Voltage

DC Transmission Line

6. Characteristics of Some Switching Devices

a. Bipolar Transistors

b. Thyristors

c. MOSFET Devices

7. Inverter Circuit Used in this Exercise

8. Bibliography

B. EXPERIMENT

1. Equipment List

2. Procedure

a. General Instructions

b. Principles of Circuit Operation

c. No Load Frequency Response

d. Efficiency and Frequency Response with Load

C. REPORT

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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 waveshapes:

With no signal input to the inverter and an open-circuit on the output (infinite load resistance) observe and copy the FET gate voltages A and A’ on CH1 and CH2 of the oscilloscope. Also, observe and copy the voltages (( and (’) and observe and copy the difference between these voltages which the output of the inverter before the filter. Connect the two voltages (( and (’) to CH1 and CH2 and use the MATH function to display the difference.

Repeat with a 0.2 V, 10 Hz, sinusoidal signal input voltage connected to the BNC of the inverter.

b) No-load frequency 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 signal input voltage so that the output voltage is approximately 40 V peak to peak. Vary the frequency of the input voltage from 10 Hz to 2000 Hz (10, 20, 50, 100, 200, 500, 1000, 2000). Using DMM’s measure the signal input voltage and output voltage at each frequency.

c) Efficiency:

Set the load resistance to 100 Ohms. At a frequency of 60 Hz, adjust the signal input 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).

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.

b) Make a table for the no-load measurements that includes frequency, signal input voltage, output voltage and the calculated ratio of output voltage to input voltage.

Plot the ratio versus frequency. Comment on the frequency response of the inverter and the waveshape of the output.

c) Make a table for the measurements with a 100 Ohm load that includes DC voltage, DC current, calculated DC input power, AC output voltage, calculated output power and calculated efficiency.

Plot efficiency versus output voltage. Comment on the efficiency of the inverter.

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